Linux 2.6.36-rc5

[linux-2.6/get_maintainer.git] / drivers / usb / musb / musb_host.c

/*
 * MUSB OTG driver host support
 *
 * Copyright 2005 Mentor Graphics Corporation
 * Copyright (C) 2005-2006 by Texas Instruments
 * Copyright (C) 2006-2007 Nokia Corporation
 * Copyright (C) 2008-2009 MontaVista Software, Inc. <source@mvista.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 * NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/list.h>

#include "musb_core.h"
#include "musb_host.h"


/* MUSB HOST status 22-mar-2006
 *
 * - There's still lots of partial code duplication for fault paths, so
 *   they aren't handled as consistently as they need to be.
 *
 * - PIO mostly behaved when last tested.
 *     + including ep0, with all usbtest cases 9, 10
 *     + usbtest 14 (ep0out) doesn't seem to run at all
 *     + double buffered OUT/TX endpoints saw stalls(!) with certain usbtest
 *       configurations, but otherwise double buffering passes basic tests.
 *     + for 2.6.N, for N > ~10, needs API changes for hcd framework.
 *
 * - DMA (CPPI) ... partially behaves, not currently recommended
 *     + about 1/15 the speed of typical EHCI implementations (PCI)
 *     + RX, all too often reqpkt seems to misbehave after tx
 *     + TX, no known issues (other than evident silicon issue)
 *
 * - DMA (Mentor/OMAP) ...has at least toggle update problems
 *
 * - [23-feb-2009] minimal traffic scheduling to avoid bulk RX packet
 *   starvation ... nothing yet for TX, interrupt, or bulk.
 *
 * - Not tested with HNP, but some SRP paths seem to behave.
 *
 * NOTE 24-August-2006:
 *
 * - Bulk traffic finally uses both sides of hardware ep1, freeing up an
 *   extra endpoint for periodic use enabling hub + keybd + mouse.  That
 *   mostly works, except that with "usbnet" it's easy to trigger cases
 *   with "ping" where RX loses.  (a) ping to davinci, even "ping -f",
 *   fine; but (b) ping _from_ davinci, even "ping -c 1", ICMP RX loses
 *   although ARP RX wins.  (That test was done with a full speed link.)
 */


/*
 * NOTE on endpoint usage:
 *
 * CONTROL transfers all go through ep0.  BULK ones go through dedicated IN
 * and OUT endpoints ... hardware is dedicated for those "async" queue(s).
 * (Yes, bulk _could_ use more of the endpoints than that, and would even
 * benefit from it.)
 *
 * INTERUPPT and ISOCHRONOUS transfers are scheduled to the other endpoints.
 * So far that scheduling is both dumb and optimistic:  the endpoint will be
 * "claimed" until its software queue is no longer refilled.  No multiplexing
 * of transfers between endpoints, or anything clever.
 */


static void musb_ep_program(struct musb *musb, u8 epnum,
                        struct urb *urb, int is_out,
                        u8 *buf, u32 offset, u32 len);

/*
 * Clear TX fifo. Needed to avoid BABBLE errors.
 */
static void musb_h_tx_flush_fifo(struct musb_hw_ep *ep)
{
        void __iomem    *epio = ep->regs;
        u16             csr;
        u16             lastcsr = 0;
        int             retries = 1000;

        csr = musb_readw(epio, MUSB_TXCSR);
        while (csr & MUSB_TXCSR_FIFONOTEMPTY) {
                if (csr != lastcsr)
                        DBG(3, "Host TX FIFONOTEMPTY csr: %02x\n", csr);
                lastcsr = csr;
                csr |= MUSB_TXCSR_FLUSHFIFO;
                musb_writew(epio, MUSB_TXCSR, csr);
                csr = musb_readw(epio, MUSB_TXCSR);
                if (WARN(retries-- < 1,
                                "Could not flush host TX%d fifo: csr: %04x\n",
                                ep->epnum, csr))
                        return;
                mdelay(1);
        }
}

static void musb_h_ep0_flush_fifo(struct musb_hw_ep *ep)
{
        void __iomem    *epio = ep->regs;
        u16             csr;
        int             retries = 5;

        /* scrub any data left in the fifo */
        do {
                csr = musb_readw(epio, MUSB_TXCSR);
                if (!(csr & (MUSB_CSR0_TXPKTRDY | MUSB_CSR0_RXPKTRDY)))
                        break;
                musb_writew(epio, MUSB_TXCSR, MUSB_CSR0_FLUSHFIFO);
                csr = musb_readw(epio, MUSB_TXCSR);
                udelay(10);
        } while (--retries);

        WARN(!retries, "Could not flush host TX%d fifo: csr: %04x\n",
                        ep->epnum, csr);

        /* and reset for the next transfer */
        musb_writew(epio, MUSB_TXCSR, 0);
}

/*
 * Start transmit. Caller is responsible for locking shared resources.
 * musb must be locked.
 */
static inline void musb_h_tx_start(struct musb_hw_ep *ep)
{
        u16     txcsr;

        /* NOTE: no locks here; caller should lock and select EP */
        if (ep->epnum) {
                txcsr = musb_readw(ep->regs, MUSB_TXCSR);
                txcsr |= MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_H_WZC_BITS;
                musb_writew(ep->regs, MUSB_TXCSR, txcsr);
        } else {
                txcsr = MUSB_CSR0_H_SETUPPKT | MUSB_CSR0_TXPKTRDY;
                musb_writew(ep->regs, MUSB_CSR0, txcsr);
        }

}

static inline void musb_h_tx_dma_start(struct musb_hw_ep *ep)
{
        u16     txcsr;

        /* NOTE: no locks here; caller should lock and select EP */
        txcsr = musb_readw(ep->regs, MUSB_TXCSR);
        txcsr |= MUSB_TXCSR_DMAENAB | MUSB_TXCSR_H_WZC_BITS;
        if (is_cppi_enabled())
                txcsr |= MUSB_TXCSR_DMAMODE;
        musb_writew(ep->regs, MUSB_TXCSR, txcsr);
}

static void musb_ep_set_qh(struct musb_hw_ep *ep, int is_in, struct musb_qh *qh)
{
        if (is_in != 0 || ep->is_shared_fifo)
                ep->in_qh  = qh;
        if (is_in == 0 || ep->is_shared_fifo)
                ep->out_qh = qh;
}

static struct musb_qh *musb_ep_get_qh(struct musb_hw_ep *ep, int is_in)
{
        return is_in ? ep->in_qh : ep->out_qh;
}

/*
 * Start the URB at the front of an endpoint's queue
 * end must be claimed from the caller.
 *
 * Context: controller locked, irqs blocked
 */
static void
musb_start_urb(struct musb *musb, int is_in, struct musb_qh *qh)
{
        u16                     frame;
        u32                     len;
        void __iomem            *mbase =  musb->mregs;
        struct urb              *urb = next_urb(qh);
        void                    *buf = urb->transfer_buffer;
        u32                     offset = 0;
        struct musb_hw_ep       *hw_ep = qh->hw_ep;
        unsigned                pipe = urb->pipe;
        u8                      address = usb_pipedevice(pipe);
        int                     epnum = hw_ep->epnum;

        /* initialize software qh state */
        qh->offset = 0;
        qh->segsize = 0;

        /* gather right source of data */
        switch (qh->type) {
        case USB_ENDPOINT_XFER_CONTROL:
                /* control transfers always start with SETUP */
                is_in = 0;
                musb->ep0_stage = MUSB_EP0_START;
                buf = urb->setup_packet;
                len = 8;
                break;
        case USB_ENDPOINT_XFER_ISOC:
                qh->iso_idx = 0;
                qh->frame = 0;
                offset = urb->iso_frame_desc[0].offset;
                len = urb->iso_frame_desc[0].length;
                break;
        default:                /* bulk, interrupt */
                /* actual_length may be nonzero on retry paths */
                buf = urb->transfer_buffer + urb->actual_length;
                len = urb->transfer_buffer_length - urb->actual_length;
        }

        DBG(4, "qh %p urb %p dev%d ep%d%s%s, hw_ep %d, %p/%d\n",
                        qh, urb, address, qh->epnum,
                        is_in ? "in" : "out",
                        ({char *s; switch (qh->type) {
                        case USB_ENDPOINT_XFER_CONTROL: s = ""; break;
                        case USB_ENDPOINT_XFER_BULK:    s = "-bulk"; break;
                        case USB_ENDPOINT_XFER_ISOC:    s = "-iso"; break;
                        default:                        s = "-intr"; break;
                        }; s; }),
                        epnum, buf + offset, len);

        /* Configure endpoint */
        musb_ep_set_qh(hw_ep, is_in, qh);
        musb_ep_program(musb, epnum, urb, !is_in, buf, offset, len);

        /* transmit may have more work: start it when it is time */
        if (is_in)
                return;

        /* determine if the time is right for a periodic transfer */
        switch (qh->type) {
        case USB_ENDPOINT_XFER_ISOC:
        case USB_ENDPOINT_XFER_INT:
                DBG(3, "check whether there's still time for periodic Tx\n");
                frame = musb_readw(mbase, MUSB_FRAME);
                /* FIXME this doesn't implement that scheduling policy ...
                 * or handle framecounter wrapping
                 */
                if ((urb->transfer_flags & URB_ISO_ASAP)
                                || (frame >= urb->start_frame)) {
                        /* REVISIT the SOF irq handler shouldn't duplicate
                         * this code; and we don't init urb->start_frame...
                         */
                        qh->frame = 0;
                        goto start;
                } else {
                        qh->frame = urb->start_frame;
                        /* enable SOF interrupt so we can count down */
                        DBG(1, "SOF for %d\n", epnum);
#if 1 /* ifndef CONFIG_ARCH_DAVINCI */
                        musb_writeb(mbase, MUSB_INTRUSBE, 0xff);
#endif
                }
                break;
        default:
start:
                DBG(4, "Start TX%d %s\n", epnum,
                        hw_ep->tx_channel ? "dma" : "pio");

                if (!hw_ep->tx_channel)
                        musb_h_tx_start(hw_ep);
                else if (is_cppi_enabled() || tusb_dma_omap())
                        musb_h_tx_dma_start(hw_ep);
        }
}

/* Context: caller owns controller lock, IRQs are blocked */
static void musb_giveback(struct musb *musb, struct urb *urb, int status)
__releases(musb->lock)
__acquires(musb->lock)
{
        DBG(({ int level; switch (status) {
                                case 0:
                                        level = 4;
                                        break;
                                /* common/boring faults */
                                case -EREMOTEIO:
                                case -ESHUTDOWN:
                                case -ECONNRESET:
                                case -EPIPE:
                                        level = 3;
                                        break;
                                default:
                                        level = 2;
                                        break;
                                }; level; }),
                        "complete %p %pF (%d), dev%d ep%d%s, %d/%d\n",
                        urb, urb->complete, status,
                        usb_pipedevice(urb->pipe),
                        usb_pipeendpoint(urb->pipe),
                        usb_pipein(urb->pipe) ? "in" : "out",
                        urb->actual_length, urb->transfer_buffer_length
                        );

        usb_hcd_unlink_urb_from_ep(musb_to_hcd(musb), urb);
        spin_unlock(&musb->lock);
        usb_hcd_giveback_urb(musb_to_hcd(musb), urb, status);
        spin_lock(&musb->lock);
}

/* For bulk/interrupt endpoints only */
static inline void musb_save_toggle(struct musb_qh *qh, int is_in,
                                    struct urb *urb)
{
        void __iomem            *epio = qh->hw_ep->regs;
        u16                     csr;

        /*
         * FIXME: the current Mentor DMA code seems to have
         * problems getting toggle correct.
         */

        if (is_in)
                csr = musb_readw(epio, MUSB_RXCSR) & MUSB_RXCSR_H_DATATOGGLE;
        else
                csr = musb_readw(epio, MUSB_TXCSR) & MUSB_TXCSR_H_DATATOGGLE;

        usb_settoggle(urb->dev, qh->epnum, !is_in, csr ? 1 : 0);
}

/*
 * Advance this hardware endpoint's queue, completing the specified URB and
 * advancing to either the next URB queued to that qh, or else invalidating
 * that qh and advancing to the next qh scheduled after the current one.
 *
 * Context: caller owns controller lock, IRQs are blocked
 */
static void musb_advance_schedule(struct musb *musb, struct urb *urb,
                                  struct musb_hw_ep *hw_ep, int is_in)
{
        struct musb_qh          *qh = musb_ep_get_qh(hw_ep, is_in);
        struct musb_hw_ep       *ep = qh->hw_ep;
        int                     ready = qh->is_ready;
        int                     status;

        status = (urb->status == -EINPROGRESS) ? 0 : urb->status;

        /* save toggle eagerly, for paranoia */
        switch (qh->type) {
        case USB_ENDPOINT_XFER_BULK:
        case USB_ENDPOINT_XFER_INT:
                musb_save_toggle(qh, is_in, urb);
                break;
        case USB_ENDPOINT_XFER_ISOC:
                if (status == 0 && urb->error_count)
                        status = -EXDEV;
                break;
        }

        qh->is_ready = 0;
        musb_giveback(musb, urb, status);
        qh->is_ready = ready;

        /* reclaim resources (and bandwidth) ASAP; deschedule it, and
         * invalidate qh as soon as list_empty(&hep->urb_list)
         */
        if (list_empty(&qh->hep->urb_list)) {
                struct list_head        *head;

                if (is_in)
                        ep->rx_reinit = 1;
                else
                        ep->tx_reinit = 1;

                /* Clobber old pointers to this qh */
                musb_ep_set_qh(ep, is_in, NULL);
                qh->hep->hcpriv = NULL;

                switch (qh->type) {

                case USB_ENDPOINT_XFER_CONTROL:
                case USB_ENDPOINT_XFER_BULK:
                        /* fifo policy for these lists, except that NAKing
                         * should rotate a qh to the end (for fairness).
                         */
                        if (qh->mux == 1) {
                                head = qh->ring.prev;
                                list_del(&qh->ring);
                                kfree(qh);
                                qh = first_qh(head);
                                break;
                        }

                case USB_ENDPOINT_XFER_ISOC:
                case USB_ENDPOINT_XFER_INT:
                        /* this is where periodic bandwidth should be
                         * de-allocated if it's tracked and allocated;
                         * and where we'd update the schedule tree...
                         */
                        kfree(qh);
                        qh = NULL;
                        break;
                }
        }

        if (qh != NULL && qh->is_ready) {
                DBG(4, "... next ep%d %cX urb %p\n",
                    hw_ep->epnum, is_in ? 'R' : 'T', next_urb(qh));
                musb_start_urb(musb, is_in, qh);
        }
}

static u16 musb_h_flush_rxfifo(struct musb_hw_ep *hw_ep, u16 csr)
{
        /* we don't want fifo to fill itself again;
         * ignore dma (various models),
         * leave toggle alone (may not have been saved yet)
         */
        csr |= MUSB_RXCSR_FLUSHFIFO | MUSB_RXCSR_RXPKTRDY;
        csr &= ~(MUSB_RXCSR_H_REQPKT
                | MUSB_RXCSR_H_AUTOREQ
                | MUSB_RXCSR_AUTOCLEAR);

        /* write 2x to allow double buffering */
        musb_writew(hw_ep->regs, MUSB_RXCSR, csr);
        musb_writew(hw_ep->regs, MUSB_RXCSR, csr);

        /* flush writebuffer */
        return musb_readw(hw_ep->regs, MUSB_RXCSR);
}

/*
 * PIO RX for a packet (or part of it).
 */
static bool
musb_host_packet_rx(struct musb *musb, struct urb *urb, u8 epnum, u8 iso_err)
{
        u16                     rx_count;
        u8                      *buf;
        u16                     csr;
        bool                    done = false;
        u32                     length;
        int                     do_flush = 0;
        struct musb_hw_ep       *hw_ep = musb->endpoints + epnum;
        void __iomem            *epio = hw_ep->regs;
        struct musb_qh          *qh = hw_ep->in_qh;
        int                     pipe = urb->pipe;
        void                    *buffer = urb->transfer_buffer;

        /* musb_ep_select(mbase, epnum); */
        rx_count = musb_readw(epio, MUSB_RXCOUNT);
        DBG(3, "RX%d count %d, buffer %p len %d/%d\n", epnum, rx_count,
                        urb->transfer_buffer, qh->offset,
                        urb->transfer_buffer_length);

        /* unload FIFO */
        if (usb_pipeisoc(pipe)) {
                int                                     status = 0;
                struct usb_iso_packet_descriptor        *d;

                if (iso_err) {
                        status = -EILSEQ;
                        urb->error_count++;
                }

                d = urb->iso_frame_desc + qh->iso_idx;
                buf = buffer + d->offset;
                length = d->length;
                if (rx_count > length) {
                        if (status == 0) {
                                status = -EOVERFLOW;
                                urb->error_count++;
                        }
                        DBG(2, "** OVERFLOW %d into %d\n", rx_count, length);
                        do_flush = 1;
                } else
                        length = rx_count;
                urb->actual_length += length;
                d->actual_length = length;

                d->status = status;

                /* see if we are done */
                done = (++qh->iso_idx >= urb->number_of_packets);
        } else {
                /* non-isoch */
                buf = buffer + qh->offset;
                length = urb->transfer_buffer_length - qh->offset;
                if (rx_count > length) {
                        if (urb->status == -EINPROGRESS)
                                urb->status = -EOVERFLOW;
                        DBG(2, "** OVERFLOW %d into %d\n", rx_count, length);
                        do_flush = 1;
                } else
                        length = rx_count;
                urb->actual_length += length;
                qh->offset += length;

                /* see if we are done */
                done = (urb->actual_length == urb->transfer_buffer_length)
                        || (rx_count < qh->maxpacket)
                        || (urb->status != -EINPROGRESS);
                if (done
                                && (urb->status == -EINPROGRESS)
                                && (urb->transfer_flags & URB_SHORT_NOT_OK)
                                && (urb->actual_length
                                        < urb->transfer_buffer_length))
                        urb->status = -EREMOTEIO;
        }

        musb_read_fifo(hw_ep, length, buf);

        csr = musb_readw(epio, MUSB_RXCSR);
        csr |= MUSB_RXCSR_H_WZC_BITS;
        if (unlikely(do_flush))
                musb_h_flush_rxfifo(hw_ep, csr);
        else {
                /* REVISIT this assumes AUTOCLEAR is never set */
                csr &= ~(MUSB_RXCSR_RXPKTRDY | MUSB_RXCSR_H_REQPKT);
                if (!done)
                        csr |= MUSB_RXCSR_H_REQPKT;
                musb_writew(epio, MUSB_RXCSR, csr);
        }

        return done;
}

/* we don't always need to reinit a given side of an endpoint...
 * when we do, use tx/rx reinit routine and then construct a new CSR
 * to address data toggle, NYET, and DMA or PIO.
 *
 * it's possible that driver bugs (especially for DMA) or aborting a
 * transfer might have left the endpoint busier than it should be.
 * the busy/not-empty tests are basically paranoia.
 */
static void
musb_rx_reinit(struct musb *musb, struct musb_qh *qh, struct musb_hw_ep *ep)
{
        u16     csr;

        /* NOTE:  we know the "rx" fifo reinit never triggers for ep0.
         * That always uses tx_reinit since ep0 repurposes TX register
         * offsets; the initial SETUP packet is also a kind of OUT.
         */

        /* if programmed for Tx, put it in RX mode */
        if (ep->is_shared_fifo) {
                csr = musb_readw(ep->regs, MUSB_TXCSR);
                if (csr & MUSB_TXCSR_MODE) {
                        musb_h_tx_flush_fifo(ep);
                        csr = musb_readw(ep->regs, MUSB_TXCSR);
                        musb_writew(ep->regs, MUSB_TXCSR,
                                    csr | MUSB_TXCSR_FRCDATATOG);
                }

                /*
                 * Clear the MODE bit (and everything else) to enable Rx.
                 * NOTE: we mustn't clear the DMAMODE bit before DMAENAB.
                 */
                if (csr & MUSB_TXCSR_DMAMODE)
                        musb_writew(ep->regs, MUSB_TXCSR, MUSB_TXCSR_DMAMODE);
                musb_writew(ep->regs, MUSB_TXCSR, 0);

        /* scrub all previous state, clearing toggle */
        } else {
                csr = musb_readw(ep->regs, MUSB_RXCSR);
                if (csr & MUSB_RXCSR_RXPKTRDY)
                        WARNING("rx%d, packet/%d ready?\n", ep->epnum,
                                musb_readw(ep->regs, MUSB_RXCOUNT));

                musb_h_flush_rxfifo(ep, MUSB_RXCSR_CLRDATATOG);
        }

        /* target addr and (for multipoint) hub addr/port */
        if (musb->is_multipoint) {
                musb_write_rxfunaddr(ep->target_regs, qh->addr_reg);
                musb_write_rxhubaddr(ep->target_regs, qh->h_addr_reg);
                musb_write_rxhubport(ep->target_regs, qh->h_port_reg);

        } else
                musb_writeb(musb->mregs, MUSB_FADDR, qh->addr_reg);

        /* protocol/endpoint, interval/NAKlimit, i/o size */
        musb_writeb(ep->regs, MUSB_RXTYPE, qh->type_reg);
        musb_writeb(ep->regs, MUSB_RXINTERVAL, qh->intv_reg);
        /* NOTE: bulk combining rewrites high bits of maxpacket */
        /* Set RXMAXP with the FIFO size of the endpoint
         * to disable double buffer mode.
         */
        if (musb->hwvers < MUSB_HWVERS_2000)
                musb_writew(ep->regs, MUSB_RXMAXP, ep->max_packet_sz_rx);
        else
                musb_writew(ep->regs, MUSB_RXMAXP,
                                qh->maxpacket | ((qh->hb_mult - 1) << 11));

        ep->rx_reinit = 0;
}

static bool musb_tx_dma_program(struct dma_controller *dma,
                struct musb_hw_ep *hw_ep, struct musb_qh *qh,
                struct urb *urb, u32 offset, u32 length)
{
        struct dma_channel      *channel = hw_ep->tx_channel;
        void __iomem            *epio = hw_ep->regs;
        u16                     pkt_size = qh->maxpacket;
        u16                     csr;
        u8                      mode;

#ifdef  CONFIG_USB_INVENTRA_DMA
        if (length > channel->max_len)
                length = channel->max_len;

        csr = musb_readw(epio, MUSB_TXCSR);
        if (length > pkt_size) {
                mode = 1;
                csr |= MUSB_TXCSR_DMAMODE | MUSB_TXCSR_DMAENAB;
                /* autoset shouldn't be set in high bandwidth */
                if (qh->hb_mult == 1)
                        csr |= MUSB_TXCSR_AUTOSET;
        } else {
                mode = 0;
                csr &= ~(MUSB_TXCSR_AUTOSET | MUSB_TXCSR_DMAMODE);
                csr |= MUSB_TXCSR_DMAENAB; /* against programmer's guide */
        }
        channel->desired_mode = mode;
        musb_writew(epio, MUSB_TXCSR, csr);
#else
        if (!is_cppi_enabled() && !tusb_dma_omap())
                return false;

        channel->actual_len = 0;

        /*
         * TX uses "RNDIS" mode automatically but needs help
         * to identify the zero-length-final-packet case.
         */
        mode = (urb->transfer_flags & URB_ZERO_PACKET) ? 1 : 0;
#endif

        qh->segsize = length;

        if (!dma->channel_program(channel, pkt_size, mode,
                        urb->transfer_dma + offset, length)) {
                dma->channel_release(channel);
                hw_ep->tx_channel = NULL;

                csr = musb_readw(epio, MUSB_TXCSR);
                csr &= ~(MUSB_TXCSR_AUTOSET | MUSB_TXCSR_DMAENAB);
                musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_H_WZC_BITS);
                return false;
        }
        return true;
}

/*
 * Program an HDRC endpoint as per the given URB
 * Context: irqs blocked, controller lock held
 */
static void musb_ep_program(struct musb *musb, u8 epnum,
                        struct urb *urb, int is_out,
                        u8 *buf, u32 offset, u32 len)
{
        struct dma_controller   *dma_controller;
        struct dma_channel      *dma_channel;
        u8                      dma_ok;
        void __iomem            *mbase = musb->mregs;
        struct musb_hw_ep       *hw_ep = musb->endpoints + epnum;
        void __iomem            *epio = hw_ep->regs;
        struct musb_qh          *qh = musb_ep_get_qh(hw_ep, !is_out);
        u16                     packet_sz = qh->maxpacket;

        DBG(3, "%s hw%d urb %p spd%d dev%d ep%d%s "
                                "h_addr%02x h_port%02x bytes %d\n",
                        is_out ? "-->" : "<--",
                        epnum, urb, urb->dev->speed,
                        qh->addr_reg, qh->epnum, is_out ? "out" : "in",
                        qh->h_addr_reg, qh->h_port_reg,
                        len);

        musb_ep_select(mbase, epnum);

        /* candidate for DMA? */
        dma_controller = musb->dma_controller;
        if (is_dma_capable() && epnum && dma_controller) {
                dma_channel = is_out ? hw_ep->tx_channel : hw_ep->rx_channel;
                if (!dma_channel) {
                        dma_channel = dma_controller->channel_alloc(
                                        dma_controller, hw_ep, is_out);
                        if (is_out)
                                hw_ep->tx_channel = dma_channel;
                        else
                                hw_ep->rx_channel = dma_channel;
                }
        } else
                dma_channel = NULL;

        /* make sure we clear DMAEnab, autoSet bits from previous run */

        /* OUT/transmit/EP0 or IN/receive? */
        if (is_out) {
                u16     csr;
                u16     int_txe;
                u16     load_count;

                csr = musb_readw(epio, MUSB_TXCSR);

                /* disable interrupt in case we flush */
                int_txe = musb_readw(mbase, MUSB_INTRTXE);
                musb_writew(mbase, MUSB_INTRTXE, int_txe & ~(1 << epnum));

                /* general endpoint setup */
                if (epnum) {
                        /* flush all old state, set default */
                        musb_h_tx_flush_fifo(hw_ep);

                        /*
                         * We must not clear the DMAMODE bit before or in
                         * the same cycle with the DMAENAB bit, so we clear
                         * the latter first...
                         */
                        csr &= ~(MUSB_TXCSR_H_NAKTIMEOUT
                                        | MUSB_TXCSR_AUTOSET
                                        | MUSB_TXCSR_DMAENAB
                                        | MUSB_TXCSR_FRCDATATOG
                                        | MUSB_TXCSR_H_RXSTALL
                                        | MUSB_TXCSR_H_ERROR
                                        | MUSB_TXCSR_TXPKTRDY
                                        );
                        csr |= MUSB_TXCSR_MODE;

                        if (usb_gettoggle(urb->dev, qh->epnum, 1))
                                csr |= MUSB_TXCSR_H_WR_DATATOGGLE
                                        | MUSB_TXCSR_H_DATATOGGLE;
                        else
                                csr |= MUSB_TXCSR_CLRDATATOG;

                        musb_writew(epio, MUSB_TXCSR, csr);
                        /* REVISIT may need to clear FLUSHFIFO ... */
                        csr &= ~MUSB_TXCSR_DMAMODE;
                        musb_writew(epio, MUSB_TXCSR, csr);
                        csr = musb_readw(epio, MUSB_TXCSR);
                } else {
                        /* endpoint 0: just flush */
                        musb_h_ep0_flush_fifo(hw_ep);
                }

                /* target addr and (for multipoint) hub addr/port */
                if (musb->is_multipoint) {
                        musb_write_txfunaddr(mbase, epnum, qh->addr_reg);
                        musb_write_txhubaddr(mbase, epnum, qh->h_addr_reg);
                        musb_write_txhubport(mbase, epnum, qh->h_port_reg);
/* FIXME if !epnum, do the same for RX ... */
                } else
                        musb_writeb(mbase, MUSB_FADDR, qh->addr_reg);

                /* protocol/endpoint/interval/NAKlimit */
                if (epnum) {
                        musb_writeb(epio, MUSB_TXTYPE, qh->type_reg);
                        if (can_bulk_split(musb, qh->type))
                                musb_writew(epio, MUSB_TXMAXP,
                                        packet_sz
                                        | ((hw_ep->max_packet_sz_tx /
                                                packet_sz) - 1) << 11);
                        else
                                musb_writew(epio, MUSB_TXMAXP,
                                        packet_sz);
                        musb_writeb(epio, MUSB_TXINTERVAL, qh->intv_reg);
                } else {
                        musb_writeb(epio, MUSB_NAKLIMIT0, qh->intv_reg);
                        if (musb->is_multipoint)
                                musb_writeb(epio, MUSB_TYPE0,
                                                qh->type_reg);
                }

                if (can_bulk_split(musb, qh->type))
                        load_count = min((u32) hw_ep->max_packet_sz_tx,
                                                len);
                else
                        load_count = min((u32) packet_sz, len);

                if (dma_channel && musb_tx_dma_program(dma_controller,
                                        hw_ep, qh, urb, offset, len))
                        load_count = 0;

                if (load_count) {
                        /* PIO to load FIFO */
                        qh->segsize = load_count;
                        musb_write_fifo(hw_ep, load_count, buf);
                }

                /* re-enable interrupt */
                musb_writew(mbase, MUSB_INTRTXE, int_txe);

        /* IN/receive */
        } else {
                u16     csr;

                if (hw_ep->rx_reinit) {
                        musb_rx_reinit(musb, qh, hw_ep);

                        /* init new state: toggle and NYET, maybe DMA later */
                        if (usb_gettoggle(urb->dev, qh->epnum, 0))
                                csr = MUSB_RXCSR_H_WR_DATATOGGLE
                                        | MUSB_RXCSR_H_DATATOGGLE;
                        else
                                csr = 0;
                        if (qh->type == USB_ENDPOINT_XFER_INT)
                                csr |= MUSB_RXCSR_DISNYET;

                } else {
                        csr = musb_readw(hw_ep->regs, MUSB_RXCSR);

                        if (csr & (MUSB_RXCSR_RXPKTRDY
                                        | MUSB_RXCSR_DMAENAB
                                        | MUSB_RXCSR_H_REQPKT))
                                ERR("broken !rx_reinit, ep%d csr %04x\n",
                                                hw_ep->epnum, csr);

                        /* scrub any stale state, leaving toggle alone */
                        csr &= MUSB_RXCSR_DISNYET;
                }

                /* kick things off */

                if ((is_cppi_enabled() || tusb_dma_omap()) && dma_channel) {
                        /* candidate for DMA */
                        if (dma_channel) {
                                dma_channel->actual_len = 0L;
                                qh->segsize = len;

                                /* AUTOREQ is in a DMA register */
                                musb_writew(hw_ep->regs, MUSB_RXCSR, csr);
                                csr = musb_readw(hw_ep->regs,
                                                MUSB_RXCSR);

                                /* unless caller treats short rx transfers as
                                 * errors, we dare not queue multiple transfers.
                                 */
                                dma_ok = dma_controller->channel_program(
                                                dma_channel, packet_sz,
                                                !(urb->transfer_flags
                                                        & URB_SHORT_NOT_OK),
                                                urb->transfer_dma + offset,
                                                qh->segsize);
                                if (!dma_ok) {
                                        dma_controller->channel_release(
                                                        dma_channel);
                                        hw_ep->rx_channel = NULL;
                                        dma_channel = NULL;
                                } else
                                        csr |= MUSB_RXCSR_DMAENAB;
                        }
                }

                csr |= MUSB_RXCSR_H_REQPKT;
                DBG(7, "RXCSR%d := %04x\n", epnum, csr);
                musb_writew(hw_ep->regs, MUSB_RXCSR, csr);
                csr = musb_readw(hw_ep->regs, MUSB_RXCSR);
        }
}


/*
 * Service the default endpoint (ep0) as host.
 * Return true until it's time to start the status stage.
 */
static bool musb_h_ep0_continue(struct musb *musb, u16 len, struct urb *urb)
{
        bool                     more = false;
        u8                      *fifo_dest = NULL;
        u16                     fifo_count = 0;
        struct musb_hw_ep       *hw_ep = musb->control_ep;
        struct musb_qh          *qh = hw_ep->in_qh;
        struct usb_ctrlrequest  *request;

        switch (musb->ep0_stage) {
        case MUSB_EP0_IN:
                fifo_dest = urb->transfer_buffer + urb->actual_length;
                fifo_count = min_t(size_t, len, urb->transfer_buffer_length -
                                   urb->actual_length);
                if (fifo_count < len)
                        urb->status = -EOVERFLOW;

                musb_read_fifo(hw_ep, fifo_count, fifo_dest);

                urb->actual_length += fifo_count;
                if (len < qh->maxpacket) {
                        /* always terminate on short read; it's
                         * rarely reported as an error.
                         */
                } else if (urb->actual_length <
                                urb->transfer_buffer_length)
                        more = true;
                break;
        case MUSB_EP0_START:
                request = (struct usb_ctrlrequest *) urb->setup_packet;

                if (!request->wLength) {
                        DBG(4, "start no-DATA\n");
                        break;
                } else if (request->bRequestType & USB_DIR_IN) {
                        DBG(4, "start IN-DATA\n");
                        musb->ep0_stage = MUSB_EP0_IN;
                        more = true;
                        break;
                } else {
                        DBG(4, "start OUT-DATA\n");
                        musb->ep0_stage = MUSB_EP0_OUT;
                        more = true;
                }
                /* FALLTHROUGH */
        case MUSB_EP0_OUT:
                fifo_count = min_t(size_t, qh->maxpacket,
                                   urb->transfer_buffer_length -
                                   urb->actual_length);
                if (fifo_count) {
                        fifo_dest = (u8 *) (urb->transfer_buffer
                                        + urb->actual_length);
                        DBG(3, "Sending %d byte%s to ep0 fifo %p\n",
                                        fifo_count,
                                        (fifo_count == 1) ? "" : "s",
                                        fifo_dest);
                        musb_write_fifo(hw_ep, fifo_count, fifo_dest);

                        urb->actual_length += fifo_count;
                        more = true;
                }
                break;
        default:
                ERR("bogus ep0 stage %d\n", musb->ep0_stage);
                break;
        }

        return more;
}

/*
 * Handle default endpoint interrupt as host. Only called in IRQ time
 * from musb_interrupt().
 *
 * called with controller irqlocked
 */
irqreturn_t musb_h_ep0_irq(struct musb *musb)
{
        struct urb              *urb;
        u16                     csr, len;
        int                     status = 0;
        void __iomem            *mbase = musb->mregs;
        struct musb_hw_ep       *hw_ep = musb->control_ep;
        void __iomem            *epio = hw_ep->regs;
        struct musb_qh          *qh = hw_ep->in_qh;
        bool                    complete = false;
        irqreturn_t             retval = IRQ_NONE;

        /* ep0 only has one queue, "in" */
        urb = next_urb(qh);

        musb_ep_select(mbase, 0);
        csr = musb_readw(epio, MUSB_CSR0);
        len = (csr & MUSB_CSR0_RXPKTRDY)
                        ? musb_readb(epio, MUSB_COUNT0)
                        : 0;

        DBG(4, "<== csr0 %04x, qh %p, count %d, urb %p, stage %d\n",
                csr, qh, len, urb, musb->ep0_stage);

        /* if we just did status stage, we are done */
        if (MUSB_EP0_STATUS == musb->ep0_stage) {
                retval = IRQ_HANDLED;
                complete = true;
        }

        /* prepare status */
        if (csr & MUSB_CSR0_H_RXSTALL) {
                DBG(6, "STALLING ENDPOINT\n");
                status = -EPIPE;

        } else if (csr & MUSB_CSR0_H_ERROR) {
                DBG(2, "no response, csr0 %04x\n", csr);
                status = -EPROTO;

        } else if (csr & MUSB_CSR0_H_NAKTIMEOUT) {
                DBG(2, "control NAK timeout\n");

                /* NOTE:  this code path would be a good place to PAUSE a
                 * control transfer, if another one is queued, so that
                 * ep0 is more likely to stay busy.  That's already done
                 * for bulk RX transfers.
                 *
                 * if (qh->ring.next != &musb->control), then
                 * we have a candidate... NAKing is *NOT* an error
                 */
                musb_writew(epio, MUSB_CSR0, 0);
                retval = IRQ_HANDLED;
        }

        if (status) {
                DBG(6, "aborting\n");
                retval = IRQ_HANDLED;
                if (urb)
                        urb->status = status;
                complete = true;

                /* use the proper sequence to abort the transfer */
                if (csr & MUSB_CSR0_H_REQPKT) {
                        csr &= ~MUSB_CSR0_H_REQPKT;
                        musb_writew(epio, MUSB_CSR0, csr);
                        csr &= ~MUSB_CSR0_H_NAKTIMEOUT;
                        musb_writew(epio, MUSB_CSR0, csr);
                } else {
                        musb_h_ep0_flush_fifo(hw_ep);
                }

                musb_writeb(epio, MUSB_NAKLIMIT0, 0);

                /* clear it */
                musb_writew(epio, MUSB_CSR0, 0);
        }

        if (unlikely(!urb)) {
                /* stop endpoint since we have no place for its data, this
                 * SHOULD NEVER HAPPEN! */
                ERR("no URB for end 0\n");

                musb_h_ep0_flush_fifo(hw_ep);
                goto done;
        }

        if (!complete) {
                /* call common logic and prepare response */
                if (musb_h_ep0_continue(musb, len, urb)) {
                        /* more packets required */
                        csr = (MUSB_EP0_IN == musb->ep0_stage)
                                ?  MUSB_CSR0_H_REQPKT : MUSB_CSR0_TXPKTRDY;
                } else {
                        /* data transfer complete; perform status phase */
                        if (usb_pipeout(urb->pipe)
                                        || !urb->transfer_buffer_length)
                                csr = MUSB_CSR0_H_STATUSPKT
                                        | MUSB_CSR0_H_REQPKT;
                        else
                                csr = MUSB_CSR0_H_STATUSPKT
                                        | MUSB_CSR0_TXPKTRDY;

                        /* flag status stage */
                        musb->ep0_stage = MUSB_EP0_STATUS;

                        DBG(5, "ep0 STATUS, csr %04x\n", csr);

                }
                musb_writew(epio, MUSB_CSR0, csr);
                retval = IRQ_HANDLED;
        } else
                musb->ep0_stage = MUSB_EP0_IDLE;

        /* call completion handler if done */
        if (complete)
                musb_advance_schedule(musb, urb, hw_ep, 1);
done:
        return retval;
}


#ifdef CONFIG_USB_INVENTRA_DMA

/* Host side TX (OUT) using Mentor DMA works as follows:
        submit_urb ->
                - if queue was empty, Program Endpoint
                - ... which starts DMA to fifo in mode 1 or 0

        DMA Isr (transfer complete) -> TxAvail()
                - Stop DMA (~DmaEnab)   (<--- Alert ... currently happens
                                        only in musb_cleanup_urb)
                - TxPktRdy has to be set in mode 0 or for
                        short packets in mode 1.
*/

#endif

/* Service a Tx-Available or dma completion irq for the endpoint */
void musb_host_tx(struct musb *musb, u8 epnum)
{
        int                     pipe;
        bool                    done = false;
        u16                     tx_csr;
        size_t                  length = 0;
        size_t                  offset = 0;
        struct musb_hw_ep       *hw_ep = musb->endpoints + epnum;
        void __iomem            *epio = hw_ep->regs;
        struct musb_qh          *qh = hw_ep->out_qh;
        struct urb              *urb = next_urb(qh);
        u32                     status = 0;
        void __iomem            *mbase = musb->mregs;
        struct dma_channel      *dma;

        musb_ep_select(mbase, epnum);
        tx_csr = musb_readw(epio, MUSB_TXCSR);

        /* with CPPI, DMA sometimes triggers "extra" irqs */
        if (!urb) {
                DBG(4, "extra TX%d ready, csr %04x\n", epnum, tx_csr);
                return;
        }

        pipe = urb->pipe;
        dma = is_dma_capable() ? hw_ep->tx_channel : NULL;
        DBG(4, "OUT/TX%d end, csr %04x%s\n", epnum, tx_csr,
                        dma ? ", dma" : "");

        /* check for errors */
        if (tx_csr & MUSB_TXCSR_H_RXSTALL) {
                /* dma was disabled, fifo flushed */
                DBG(3, "TX end %d stall\n", epnum);

                /* stall; record URB status */
                status = -EPIPE;

        } else if (tx_csr & MUSB_TXCSR_H_ERROR) {
                /* (NON-ISO) dma was disabled, fifo flushed */
                DBG(3, "TX 3strikes on ep=%d\n", epnum);

                status = -ETIMEDOUT;

        } else if (tx_csr & MUSB_TXCSR_H_NAKTIMEOUT) {
                DBG(6, "TX end=%d device not responding\n", epnum);

                /* NOTE:  this code path would be a good place to PAUSE a
                 * transfer, if there's some other (nonperiodic) tx urb
                 * that could use this fifo.  (dma complicates it...)
                 * That's already done for bulk RX transfers.
                 *
                 * if (bulk && qh->ring.next != &musb->out_bulk), then
                 * we have a candidate... NAKing is *NOT* an error
                 */
                musb_ep_select(mbase, epnum);
                musb_writew(epio, MUSB_TXCSR,
                                MUSB_TXCSR_H_WZC_BITS
                                | MUSB_TXCSR_TXPKTRDY);
                return;
        }

        if (status) {
                if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
                        dma->status = MUSB_DMA_STATUS_CORE_ABORT;
                        (void) musb->dma_controller->channel_abort(dma);
                }

                /* do the proper sequence to abort the transfer in the
                 * usb core; the dma engine should already be stopped.
                 */
                musb_h_tx_flush_fifo(hw_ep);
                tx_csr &= ~(MUSB_TXCSR_AUTOSET
                                | MUSB_TXCSR_DMAENAB
                                | MUSB_TXCSR_H_ERROR
                                | MUSB_TXCSR_H_RXSTALL
                                | MUSB_TXCSR_H_NAKTIMEOUT
                                );

                musb_ep_select(mbase, epnum);
                musb_writew(epio, MUSB_TXCSR, tx_csr);
                /* REVISIT may need to clear FLUSHFIFO ... */
                musb_writew(epio, MUSB_TXCSR, tx_csr);
                musb_writeb(epio, MUSB_TXINTERVAL, 0);

                done = true;
        }

        /* second cppi case */
        if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
                DBG(4, "extra TX%d ready, csr %04x\n", epnum, tx_csr);
                return;
        }

        if (is_dma_capable() && dma && !status) {
                /*
                 * DMA has completed.  But if we're using DMA mode 1 (multi
                 * packet DMA), we need a terminal TXPKTRDY interrupt before
                 * we can consider this transfer completed, lest we trash
                 * its last packet when writing the next URB's data.  So we
                 * switch back to mode 0 to get that interrupt; we'll come
                 * back here once it happens.
                 */
                if (tx_csr & MUSB_TXCSR_DMAMODE) {
                        /*
                         * We shouldn't clear DMAMODE with DMAENAB set; so
                         * clear them in a safe order.  That should be OK
                         * once TXPKTRDY has been set (and I've never seen
                         * it being 0 at this moment -- DMA interrupt latency
                         * is significant) but if it hasn't been then we have
                         * no choice but to stop being polite and ignore the
                         * programmer's guide... :-)
                         *
                         * Note that we must write TXCSR with TXPKTRDY cleared
                         * in order not to re-trigger the packet send (this bit
                         * can't be cleared by CPU), and there's another caveat:
                         * TXPKTRDY may be set shortly and then cleared in the
                         * double-buffered FIFO mode, so we do an extra TXCSR
                         * read for debouncing...
                         */
                        tx_csr &= musb_readw(epio, MUSB_TXCSR);
                        if (tx_csr & MUSB_TXCSR_TXPKTRDY) {
                                tx_csr &= ~(MUSB_TXCSR_DMAENAB |
                                            MUSB_TXCSR_TXPKTRDY);
                                musb_writew(epio, MUSB_TXCSR,
                                            tx_csr | MUSB_TXCSR_H_WZC_BITS);
                        }
                        tx_csr &= ~(MUSB_TXCSR_DMAMODE |
                                    MUSB_TXCSR_TXPKTRDY);
                        musb_writew(epio, MUSB_TXCSR,
                                    tx_csr | MUSB_TXCSR_H_WZC_BITS);

                        /*
                         * There is no guarantee that we'll get an interrupt
                         * after clearing DMAMODE as we might have done this
                         * too late (after TXPKTRDY was cleared by controller).
                         * Re-read TXCSR as we have spoiled its previous value.
                         */
                        tx_csr = musb_readw(epio, MUSB_TXCSR);
                }

                /*
                 * We may get here from a DMA completion or TXPKTRDY interrupt.
                 * In any case, we must check the FIFO status here and bail out
                 * only if the FIFO still has data -- that should prevent the
                 * "missed" TXPKTRDY interrupts and deal with double-buffered
                 * FIFO mode too...
                 */
                if (tx_csr & (MUSB_TXCSR_FIFONOTEMPTY | MUSB_TXCSR_TXPKTRDY)) {
                        DBG(2, "DMA complete but packet still in FIFO, "
                            "CSR %04x\n", tx_csr);
                        return;
                }
        }

        if (!status || dma || usb_pipeisoc(pipe)) {
                if (dma)
                        length = dma->actual_len;
                else
                        length = qh->segsize;
                qh->offset += length;

                if (usb_pipeisoc(pipe)) {
                        struct usb_iso_packet_descriptor        *d;

                        d = urb->iso_frame_desc + qh->iso_idx;
                        d->actual_length = length;
                        d->status = status;
                        if (++qh->iso_idx >= urb->number_of_packets) {
                                done = true;
                        } else {
                                d++;
                                offset = d->offset;
                                length = d->length;
                        }
                } else if (dma) {
                        done = true;
                } else {
                        /* see if we need to send more data, or ZLP */
                        if (qh->segsize < qh->maxpacket)
                                done = true;
                        else if (qh->offset == urb->transfer_buffer_length
                                        && !(urb->transfer_flags
                                                & URB_ZERO_PACKET))
                                done = true;
                        if (!done) {
                                offset = qh->offset;
                                length = urb->transfer_buffer_length - offset;
                        }
                }
        }

        /* urb->status != -EINPROGRESS means request has been faulted,
         * so we must abort this transfer after cleanup
         */
        if (urb->status != -EINPROGRESS) {
                done = true;
                if (status == 0)
                        status = urb->status;
        }

        if (done) {
                /* set status */
                urb->status = status;
                urb->actual_length = qh->offset;
                musb_advance_schedule(musb, urb, hw_ep, USB_DIR_OUT);
                return;
        } else  if (usb_pipeisoc(pipe) && dma) {
                if (musb_tx_dma_program(musb->dma_controller, hw_ep, qh, urb,
                                offset, length)) {
                        if (is_cppi_enabled() || tusb_dma_omap())
                                musb_h_tx_dma_start(hw_ep);
                        return;
                }
        } else  if (tx_csr & MUSB_TXCSR_DMAENAB) {
                DBG(1, "not complete, but DMA enabled?\n");
                return;
        }

        /*
         * PIO: start next packet in this URB.
         *
         * REVISIT: some docs say that when hw_ep->tx_double_buffered,
         * (and presumably, FIFO is not half-full) we should write *two*
         * packets before updating TXCSR; other docs disagree...
         */
        if (length > qh->maxpacket)
                length = qh->maxpacket;
        musb_write_fifo(hw_ep, length, urb->transfer_buffer + offset);
        qh->segsize = length;

        musb_ep_select(mbase, epnum);
        musb_writew(epio, MUSB_TXCSR,
                        MUSB_TXCSR_H_WZC_BITS | MUSB_TXCSR_TXPKTRDY);
}


#ifdef CONFIG_USB_INVENTRA_DMA

/* Host side RX (IN) using Mentor DMA works as follows:
        submit_urb ->
                - if queue was empty, ProgramEndpoint
                - first IN token is sent out (by setting ReqPkt)
        LinuxIsr -> RxReady()
        /\      => first packet is received
        |       - Set in mode 0 (DmaEnab, ~ReqPkt)
        |               -> DMA Isr (transfer complete) -> RxReady()
        |                   - Ack receive (~RxPktRdy), turn off DMA (~DmaEnab)
        |                   - if urb not complete, send next IN token (ReqPkt)
        |                          |            else complete urb.
        |                          |
        ---------------------------
 *
 * Nuances of mode 1:
 *      For short packets, no ack (+RxPktRdy) is sent automatically
 *      (even if AutoClear is ON)
 *      For full packets, ack (~RxPktRdy) and next IN token (+ReqPkt) is sent
 *      automatically => major problem, as collecting the next packet becomes
 *      difficult. Hence mode 1 is not used.
 *
 * REVISIT
 *      All we care about at this driver level is that
 *       (a) all URBs terminate with REQPKT cleared and fifo(s) empty;
 *       (b) termination conditions are: short RX, or buffer full;
 *       (c) fault modes include
 *           - iff URB_SHORT_NOT_OK, short RX status is -EREMOTEIO.
 *             (and that endpoint's dma queue stops immediately)
 *           - overflow (full, PLUS more bytes in the terminal packet)
 *
 *      So for example, usb-storage sets URB_SHORT_NOT_OK, and would
 *      thus be a great candidate for using mode 1 ... for all but the
 *      last packet of one URB's transfer.
 */

#endif

/* Schedule next QH from musb->in_bulk and move the current qh to
 * the end; avoids starvation for other endpoints.
 */
static void musb_bulk_rx_nak_timeout(struct musb *musb, struct musb_hw_ep *ep)
{
        struct dma_channel      *dma;
        struct urb              *urb;
        void __iomem            *mbase = musb->mregs;
        void __iomem            *epio = ep->regs;
        struct musb_qh          *cur_qh, *next_qh;
        u16                     rx_csr;

        musb_ep_select(mbase, ep->epnum);
        dma = is_dma_capable() ? ep->rx_channel : NULL;

        /* clear nak timeout bit */
        rx_csr = musb_readw(epio, MUSB_RXCSR);
        rx_csr |= MUSB_RXCSR_H_WZC_BITS;
        rx_csr &= ~MUSB_RXCSR_DATAERROR;
        musb_writew(epio, MUSB_RXCSR, rx_csr);

        cur_qh = first_qh(&musb->in_bulk);
        if (cur_qh) {
                urb = next_urb(cur_qh);
                if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
                        dma->status = MUSB_DMA_STATUS_CORE_ABORT;
                        musb->dma_controller->channel_abort(dma);
                        urb->actual_length += dma->actual_len;
                        dma->actual_len = 0L;
                }
                musb_save_toggle(cur_qh, 1, urb);

                /* move cur_qh to end of queue */
                list_move_tail(&cur_qh->ring, &musb->in_bulk);

                /* get the next qh from musb->in_bulk */
                next_qh = first_qh(&musb->in_bulk);

                /* set rx_reinit and schedule the next qh */
                ep->rx_reinit = 1;
                musb_start_urb(musb, 1, next_qh);
        }
}

/*
 * Service an RX interrupt for the given IN endpoint; docs cover bulk, iso,
 * and high-bandwidth IN transfer cases.
 */
void musb_host_rx(struct musb *musb, u8 epnum)
{
        struct urb              *urb;
        struct musb_hw_ep       *hw_ep = musb->endpoints + epnum;
        void __iomem            *epio = hw_ep->regs;
        struct musb_qh          *qh = hw_ep->in_qh;
        size_t                  xfer_len;
        void __iomem            *mbase = musb->mregs;
        int                     pipe;
        u16                     rx_csr, val;
        bool                    iso_err = false;
        bool                    done = false;
        u32                     status;
        struct dma_channel      *dma;

        musb_ep_select(mbase, epnum);

        urb = next_urb(qh);
        dma = is_dma_capable() ? hw_ep->rx_channel : NULL;
        status = 0;
        xfer_len = 0;

        rx_csr = musb_readw(epio, MUSB_RXCSR);
        val = rx_csr;

        if (unlikely(!urb)) {
                /* REVISIT -- THIS SHOULD NEVER HAPPEN ... but, at least
                 * usbtest #11 (unlinks) triggers it regularly, sometimes
                 * with fifo full.  (Only with DMA??)
                 */
                DBG(3, "BOGUS RX%d ready, csr %04x, count %d\n", epnum, val,
                        musb_readw(epio, MUSB_RXCOUNT));
                musb_h_flush_rxfifo(hw_ep, MUSB_RXCSR_CLRDATATOG);
                return;
        }

        pipe = urb->pipe;

        DBG(5, "<== hw %d rxcsr %04x, urb actual %d (+dma %zu)\n",
                epnum, rx_csr, urb->actual_length,
                dma ? dma->actual_len : 0);

        /* check for errors, concurrent stall & unlink is not really
         * handled yet! */
        if (rx_csr & MUSB_RXCSR_H_RXSTALL) {
                DBG(3, "RX end %d STALL\n", epnum);

                /* stall; record URB status */
                status = -EPIPE;

        } else if (rx_csr & MUSB_RXCSR_H_ERROR) {
                DBG(3, "end %d RX proto error\n", epnum);

                status = -EPROTO;
                musb_writeb(epio, MUSB_RXINTERVAL, 0);

        } else if (rx_csr & MUSB_RXCSR_DATAERROR) {

                if (USB_ENDPOINT_XFER_ISOC != qh->type) {
                        DBG(6, "RX end %d NAK timeout\n", epnum);

                        /* NOTE: NAKing is *NOT* an error, so we want to
                         * continue.  Except ... if there's a request for
                         * another QH, use that instead of starving it.
                         *
                         * Devices like Ethernet and serial adapters keep
                         * reads posted at all times, which will starve
                         * other devices without this logic.
                         */
                        if (usb_pipebulk(urb->pipe)
                                        && qh->mux == 1
                                        && !list_is_singular(&musb->in_bulk)) {
                                musb_bulk_rx_nak_timeout(musb, hw_ep);
                                return;
                        }
                        musb_ep_select(mbase, epnum);
                        rx_csr |= MUSB_RXCSR_H_WZC_BITS;
                        rx_csr &= ~MUSB_RXCSR_DATAERROR;
                        musb_writew(epio, MUSB_RXCSR, rx_csr);

                        goto finish;
                } else {
                        DBG(4, "RX end %d ISO data error\n", epnum);
                        /* packet error reported later */
                        iso_err = true;
                }
        } else if (rx_csr & MUSB_RXCSR_INCOMPRX) {
                DBG(3, "end %d high bandwidth incomplete ISO packet RX\n",
                                epnum);
                status = -EPROTO;
        }

        /* faults abort the transfer */
        if (status) {
                /* clean up dma and collect transfer count */
                if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
                        dma->status = MUSB_DMA_STATUS_CORE_ABORT;
                        (void) musb->dma_controller->channel_abort(dma);
                        xfer_len = dma->actual_len;
                }
                musb_h_flush_rxfifo(hw_ep, MUSB_RXCSR_CLRDATATOG);
                musb_writeb(epio, MUSB_RXINTERVAL, 0);
                done = true;
                goto finish;
        }

        if (unlikely(dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY)) {
                /* SHOULD NEVER HAPPEN ... but at least DaVinci has done it */
                ERR("RX%d dma busy, csr %04x\n", epnum, rx_csr);
                goto finish;
        }

        /* thorough shutdown for now ... given more precise fault handling
         * and better queueing support, we might keep a DMA pipeline going
         * while processing this irq for earlier completions.
         */

        /* FIXME this is _way_ too much in-line logic for Mentor DMA */

#ifndef CONFIG_USB_INVENTRA_DMA
        if (rx_csr & MUSB_RXCSR_H_REQPKT)  {
                /* REVISIT this happened for a while on some short reads...
                 * the cleanup still needs investigation... looks bad...
                 * and also duplicates dma cleanup code above ... plus,
                 * shouldn't this be the "half full" double buffer case?
                 */
                if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
                        dma->status = MUSB_DMA_STATUS_CORE_ABORT;
                        (void) musb->dma_controller->channel_abort(dma);
                        xfer_len = dma->actual_len;
                        done = true;
                }

                DBG(2, "RXCSR%d %04x, reqpkt, len %zu%s\n", epnum, rx_csr,
                                xfer_len, dma ? ", dma" : "");
                rx_csr &= ~MUSB_RXCSR_H_REQPKT;

                musb_ep_select(mbase, epnum);
                musb_writew(epio, MUSB_RXCSR,
                                MUSB_RXCSR_H_WZC_BITS | rx_csr);
        }
#endif
        if (dma && (rx_csr & MUSB_RXCSR_DMAENAB)) {
                xfer_len = dma->actual_len;

                val &= ~(MUSB_RXCSR_DMAENAB
                        | MUSB_RXCSR_H_AUTOREQ
                        | MUSB_RXCSR_AUTOCLEAR
                        | MUSB_RXCSR_RXPKTRDY);
                musb_writew(hw_ep->regs, MUSB_RXCSR, val);

#ifdef CONFIG_USB_INVENTRA_DMA
                if (usb_pipeisoc(pipe)) {
                        struct usb_iso_packet_descriptor *d;

                        d = urb->iso_frame_desc + qh->iso_idx;
                        d->actual_length = xfer_len;

                        /* even if there was an error, we did the dma
                         * for iso_frame_desc->length
                         */
                        if (d->status != EILSEQ && d->status != -EOVERFLOW)
                                d->status = 0;

                        if (++qh->iso_idx >= urb->number_of_packets)
                                done = true;
                        else
                                done = false;

                } else  {
                /* done if urb buffer is full or short packet is recd */
                done = (urb->actual_length + xfer_len >=
                                urb->transfer_buffer_length
                        || dma->actual_len < qh->maxpacket);
                }

                /* send IN token for next packet, without AUTOREQ */
                if (!done) {
                        val |= MUSB_RXCSR_H_REQPKT;
                        musb_writew(epio, MUSB_RXCSR,
                                MUSB_RXCSR_H_WZC_BITS | val);
                }

                DBG(4, "ep %d dma %s, rxcsr %04x, rxcount %d\n", epnum,
                        done ? "off" : "reset",
                        musb_readw(epio, MUSB_RXCSR),
                        musb_readw(epio, MUSB_RXCOUNT));
#else
                done = true;
#endif
        } else if (urb->status == -EINPROGRESS) {
                /* if no errors, be sure a packet is ready for unloading */
                if (unlikely(!(rx_csr & MUSB_RXCSR_RXPKTRDY))) {
                        status = -EPROTO;
                        ERR("Rx interrupt with no errors or packet!\n");

                        /* FIXME this is another "SHOULD NEVER HAPPEN" */

/* SCRUB (RX) */
                        /* do the proper sequence to abort the transfer */
                        musb_ep_select(mbase, epnum);
                        val &= ~MUSB_RXCSR_H_REQPKT;
                        musb_writew(epio, MUSB_RXCSR, val);
                        goto finish;
                }

                /* we are expecting IN packets */
#ifdef CONFIG_USB_INVENTRA_DMA
                if (dma) {
                        struct dma_controller   *c;
                        u16                     rx_count;
                        int                     ret, length;
                        dma_addr_t              buf;

                        rx_count = musb_readw(epio, MUSB_RXCOUNT);

                        DBG(2, "RX%d count %d, buffer 0x%x len %d/%d\n",
                                        epnum, rx_count,
                                        urb->transfer_dma
                                                + urb->actual_length,
                                        qh->offset,
                                        urb->transfer_buffer_length);

                        c = musb->dma_controller;

                        if (usb_pipeisoc(pipe)) {
                                int d_status = 0;
                                struct usb_iso_packet_descriptor *d;

                                d = urb->iso_frame_desc + qh->iso_idx;

                                if (iso_err) {
                                        d_status = -EILSEQ;
                                        urb->error_count++;
                                }
                                if (rx_count > d->length) {
                                        if (d_status == 0) {
                                                d_status = -EOVERFLOW;
                                                urb->error_count++;
                                        }
                                        DBG(2, "** OVERFLOW %d into %d\n",\
                                            rx_count, d->length);

                                        length = d->length;
                                } else
                                        length = rx_count;
                                d->status = d_status;
                                buf = urb->transfer_dma + d->offset;
                        } else {
                                length = rx_count;
                                buf = urb->transfer_dma +
                                                urb->actual_length;
                        }

                        dma->desired_mode = 0;
#ifdef USE_MODE1
                        /* because of the issue below, mode 1 will
                         * only rarely behave with correct semantics.
                         */
                        if ((urb->transfer_flags &
                                                URB_SHORT_NOT_OK)
                                && (urb->transfer_buffer_length -
                                                urb->actual_length)
                                        > qh->maxpacket)
                                dma->desired_mode = 1;
                        if (rx_count < hw_ep->max_packet_sz_rx) {
                                length = rx_count;
                                dma->desired_mode = 0;
                        } else {
                                length = urb->transfer_buffer_length;
                        }
#endif

/* Disadvantage of using mode 1:
 *      It's basically usable only for mass storage class; essentially all
 *      other protocols also terminate transfers on short packets.
 *
 * Details:
 *      An extra IN token is sent at the end of the transfer (due to AUTOREQ)
 *      If you try to use mode 1 for (transfer_buffer_length - 512), and try
 *      to use the extra IN token to grab the last packet using mode 0, then
 *      the problem is that you cannot be sure when the device will send the
 *      last packet and RxPktRdy set. Sometimes the packet is recd too soon
 *      such that it gets lost when RxCSR is re-set at the end of the mode 1
 *      transfer, while sometimes it is recd just a little late so that if you
 *      try to configure for mode 0 soon after the mode 1 transfer is
 *      completed, you will find rxcount 0. Okay, so you might think why not
 *      wait for an interrupt when the pkt is recd. Well, you won't get any!
 */

                        val = musb_readw(epio, MUSB_RXCSR);
                        val &= ~MUSB_RXCSR_H_REQPKT;

                        if (dma->desired_mode == 0)
                                val &= ~MUSB_RXCSR_H_AUTOREQ;
                        else
                                val |= MUSB_RXCSR_H_AUTOREQ;
                        val |= MUSB_RXCSR_DMAENAB;

                        /* autoclear shouldn't be set in high bandwidth */
                        if (qh->hb_mult == 1)
                                val |= MUSB_RXCSR_AUTOCLEAR;

                        musb_writew(epio, MUSB_RXCSR,
                                MUSB_RXCSR_H_WZC_BITS | val);

                        /* REVISIT if when actual_length != 0,
                         * transfer_buffer_length needs to be
                         * adjusted first...
                         */
                        ret = c->channel_program(
                                dma, qh->maxpacket,
                                dma->desired_mode, buf, length);

                        if (!ret) {
                                c->channel_release(dma);
                                hw_ep->rx_channel = NULL;
                                dma = NULL;
                                /* REVISIT reset CSR */
                        }
                }
#endif  /* Mentor DMA */

                if (!dma) {
                        done = musb_host_packet_rx(musb, urb,
                                        epnum, iso_err);
                        DBG(6, "read %spacket\n", done ? "last " : "");
                }
        }

finish:
        urb->actual_length += xfer_len;
        qh->offset += xfer_len;
        if (done) {
                if (urb->status == -EINPROGRESS)
                        urb->status = status;
                musb_advance_schedule(musb, urb, hw_ep, USB_DIR_IN);
        }
}

/* schedule nodes correspond to peripheral endpoints, like an OHCI QH.
 * the software schedule associates multiple such nodes with a given
 * host side hardware endpoint + direction; scheduling may activate
 * that hardware endpoint.
 */
static int musb_schedule(
        struct musb             *musb,
        struct musb_qh          *qh,
        int                     is_in)
{
        int                     idle;
        int                     best_diff;
        int                     best_end, epnum;
        struct musb_hw_ep       *hw_ep = NULL;
        struct list_head        *head = NULL;
        u8                      toggle;
        u8                      txtype;
        struct urb              *urb = next_urb(qh);

        /* use fixed hardware for control and bulk */
        if (qh->type == USB_ENDPOINT_XFER_CONTROL) {
                head = &musb->control;
                hw_ep = musb->control_ep;
                goto success;
        }

        /* else, periodic transfers get muxed to other endpoints */

        /*
         * We know this qh hasn't been scheduled, so all we need to do
         * is choose which hardware endpoint to put it on ...
         *
         * REVISIT what we really want here is a regular schedule tree
         * like e.g. OHCI uses.
         */
        best_diff = 4096;
        best_end = -1;

        for (epnum = 1, hw_ep = musb->endpoints + 1;
                        epnum < musb->nr_endpoints;
                        epnum++, hw_ep++) {
                int     diff;

                if (musb_ep_get_qh(hw_ep, is_in) != NULL)
                        continue;

                if (hw_ep == musb->bulk_ep)
                        continue;

                if (is_in)
                        diff = hw_ep->max_packet_sz_rx;
                else
                        diff = hw_ep->max_packet_sz_tx;
                diff -= (qh->maxpacket * qh->hb_mult);

                if (diff >= 0 && best_diff > diff) {

                        /*
                         * Mentor controller has a bug in that if we schedule
                         * a BULK Tx transfer on an endpoint that had earlier
                         * handled ISOC then the BULK transfer has to start on
                         * a zero toggle.  If the BULK transfer starts on a 1
                         * toggle then this transfer will fail as the mentor
                         * controller starts the Bulk transfer on a 0 toggle
                         * irrespective of the programming of the toggle bits
                         * in the TXCSR register.  Check for this condition
                         * while allocating the EP for a Tx Bulk transfer.  If
                         * so skip this EP.
                         */
                        hw_ep = musb->endpoints + epnum;
                        toggle = usb_gettoggle(urb->dev, qh->epnum, !is_in);
                        txtype = (musb_readb(hw_ep->regs, MUSB_TXTYPE)
                                        >> 4) & 0x3;
                        if (!is_in && (qh->type == USB_ENDPOINT_XFER_BULK) &&
                                toggle && (txtype == USB_ENDPOINT_XFER_ISOC))
                                continue;

                        best_diff = diff;
                        best_end = epnum;
                }
        }
        /* use bulk reserved ep1 if no other ep is free */
        if (best_end < 0 && qh->type == USB_ENDPOINT_XFER_BULK) {
                hw_ep = musb->bulk_ep;
                if (is_in)
                        head = &musb->in_bulk;
                else
                        head = &musb->out_bulk;

                /* Enable bulk RX NAK timeout scheme when bulk requests are
                 * multiplexed.  This scheme doen't work in high speed to full
                 * speed scenario as NAK interrupts are not coming from a
                 * full speed device connected to a high speed device.
                 * NAK timeout interval is 8 (128 uframe or 16ms) for HS and
                 * 4 (8 frame or 8ms) for FS device.
                 */
                if (is_in && qh->dev)
                        qh->intv_reg =
                                (USB_SPEED_HIGH == qh->dev->speed) ? 8 : 4;
                goto success;
        } else if (best_end < 0) {
                return -ENOSPC;
        }

        idle = 1;
        qh->mux = 0;
        hw_ep = musb->endpoints + best_end;
        DBG(4, "qh %p periodic slot %d\n", qh, best_end);
success:
        if (head) {
                idle = list_empty(head);
                list_add_tail(&qh->ring, head);
                qh->mux = 1;
        }
        qh->hw_ep = hw_ep;
        qh->hep->hcpriv = qh;
        if (idle)
                musb_start_urb(musb, is_in, qh);
        return 0;
}

static int musb_urb_enqueue(
        struct usb_hcd                  *hcd,
        struct urb                      *urb,
        gfp_t                           mem_flags)
{
        unsigned long                   flags;
        struct musb                     *musb = hcd_to_musb(hcd);
        struct usb_host_endpoint        *hep = urb->ep;
        struct musb_qh                  *qh;
        struct usb_endpoint_descriptor  *epd = &hep->desc;
        int                             ret;
        unsigned                        type_reg;
        unsigned                        interval;

        /* host role must be active */
        if (!is_host_active(musb) || !musb->is_active)
                return -ENODEV;

        spin_lock_irqsave(&musb->lock, flags);
        ret = usb_hcd_link_urb_to_ep(hcd, urb);
        qh = ret ? NULL : hep->hcpriv;
        if (qh)
                urb->hcpriv = qh;
        spin_unlock_irqrestore(&musb->lock, flags);

        /* DMA mapping was already done, if needed, and this urb is on
         * hep->urb_list now ... so we're done, unless hep wasn't yet
         * scheduled onto a live qh.
         *
         * REVISIT best to keep hep->hcpriv valid until the endpoint gets
         * disabled, testing for empty qh->ring and avoiding qh setup costs
         * except for the first urb queued after a config change.
         */
        if (qh || ret)
                return ret;

        /* Allocate and initialize qh, minimizing the work done each time
         * hw_ep gets reprogrammed, or with irqs blocked.  Then schedule it.
         *
         * REVISIT consider a dedicated qh kmem_cache, so it's harder
         * for bugs in other kernel code to break this driver...
         */
        qh = kzalloc(sizeof *qh, mem_flags);
        if (!qh) {
                spin_lock_irqsave(&musb->lock, flags);
                usb_hcd_unlink_urb_from_ep(hcd, urb);
                spin_unlock_irqrestore(&musb->lock, flags);
                return -ENOMEM;
        }

        qh->hep = hep;
        qh->dev = urb->dev;
        INIT_LIST_HEAD(&qh->ring);
        qh->is_ready = 1;

        qh->maxpacket = le16_to_cpu(epd->wMaxPacketSize);
        qh->type = usb_endpoint_type(epd);

        /* Bits 11 & 12 of wMaxPacketSize encode high bandwidth multiplier.
         * Some musb cores don't support high bandwidth ISO transfers; and
         * we don't (yet!) support high bandwidth interrupt transfers.
         */
        qh->hb_mult = 1 + ((qh->maxpacket >> 11) & 0x03);
        if (qh->hb_mult > 1) {
                int ok = (qh->type == USB_ENDPOINT_XFER_ISOC);

                if (ok)
                        ok = (usb_pipein(urb->pipe) && musb->hb_iso_rx)
                                || (usb_pipeout(urb->pipe) && musb->hb_iso_tx);
                if (!ok) {
                        ret = -EMSGSIZE;
                        goto done;
                }
                qh->maxpacket &= 0x7ff;
        }

        qh->epnum = usb_endpoint_num(epd);

        /* NOTE: urb->dev->devnum is wrong during SET_ADDRESS */
        qh->addr_reg = (u8) usb_pipedevice(urb->pipe);

        /* precompute rxtype/txtype/type0 register */
        type_reg = (qh->type << 4) | qh->epnum;
        switch (urb->dev->speed) {
        case USB_SPEED_LOW:
                type_reg |= 0xc0;
                break;
        case USB_SPEED_FULL:
                type_reg |= 0x80;
                break;
        default:
                type_reg |= 0x40;
        }
        qh->type_reg = type_reg;

        /* Precompute RXINTERVAL/TXINTERVAL register */
        switch (qh->type) {
        case USB_ENDPOINT_XFER_INT:
                /*
                 * Full/low speeds use the  linear encoding,
                 * high speed uses the logarithmic encoding.
                 */
                if (urb->dev->speed <= USB_SPEED_FULL) {
                        interval = max_t(u8, epd->bInterval, 1);
                        break;
                }
                /* FALLTHROUGH */
        case USB_ENDPOINT_XFER_ISOC:
                /* ISO always uses logarithmic encoding */
                interval = min_t(u8, epd->bInterval, 16);
                break;
        default:
                /* REVISIT we actually want to use NAK limits, hinting to the
                 * transfer scheduling logic to try some other qh, e.g. try
                 * for 2 msec first:
                 *
                 * interval = (USB_SPEED_HIGH == urb->dev->speed) ? 16 : 2;
                 *
                 * The downside of disabling this is that transfer scheduling
                 * gets VERY unfair for nonperiodic transfers; a misbehaving
                 * peripheral could make that hurt.  That's perfectly normal
                 * for reads from network or serial adapters ... so we have
                 * partial NAKlimit support for bulk RX.
                 *
                 * The upside of disabling it is simpler transfer scheduling.
                 */
                interval = 0;
        }
        qh->intv_reg = interval;

        /* precompute addressing for external hub/tt ports */
        if (musb->is_multipoint) {
                struct usb_device       *parent = urb->dev->parent;

                if (parent != hcd->self.root_hub) {
                        qh->h_addr_reg = (u8) parent->devnum;

                        /* set up tt info if needed */
                        if (urb->dev->tt) {
                                qh->h_port_reg = (u8) urb->dev->ttport;
                                if (urb->dev->tt->hub)
                                        qh->h_addr_reg =
                                                (u8) urb->dev->tt->hub->devnum;
                                if (urb->dev->tt->multi)
                                        qh->h_addr_reg |= 0x80;
                        }
                }
        }

        /* invariant: hep->hcpriv is null OR the qh that's already scheduled.
         * until we get real dma queues (with an entry for each urb/buffer),
         * we only have work to do in the former case.
         */
        spin_lock_irqsave(&musb->lock, flags);
        if (hep->hcpriv) {
                /* some concurrent activity submitted another urb to hep...
                 * odd, rare, error prone, but legal.
                 */
                kfree(qh);
                qh = NULL;
                ret = 0;
        } else
                ret = musb_schedule(musb, qh,
                                epd->bEndpointAddress & USB_ENDPOINT_DIR_MASK);

        if (ret == 0) {
                urb->hcpriv = qh;
                /* FIXME set urb->start_frame for iso/intr, it's tested in
                 * musb_start_urb(), but otherwise only konicawc cares ...
                 */
        }
        spin_unlock_irqrestore(&musb->lock, flags);

done:
        if (ret != 0) {
                spin_lock_irqsave(&musb->lock, flags);
                usb_hcd_unlink_urb_from_ep(hcd, urb);
                spin_unlock_irqrestore(&musb->lock, flags);
                kfree(qh);
        }
        return ret;
}


/*
 * abort a transfer that's at the head of a hardware queue.
 * called with controller locked, irqs blocked
 * that hardware queue advances to the next transfer, unless prevented
 */
static int musb_cleanup_urb(struct urb *urb, struct musb_qh *qh)
{
        struct musb_hw_ep       *ep = qh->hw_ep;
        void __iomem            *epio = ep->regs;
        unsigned                hw_end = ep->epnum;
        void __iomem            *regs = ep->musb->mregs;
        int                     is_in = usb_pipein(urb->pipe);
        int                     status = 0;
        u16                     csr;

        musb_ep_select(regs, hw_end);

        if (is_dma_capable()) {
                struct dma_channel      *dma;

                dma = is_in ? ep->rx_channel : ep->tx_channel;
                if (dma) {
                        status = ep->musb->dma_controller->channel_abort(dma);
                        DBG(status ? 1 : 3,
                                "abort %cX%d DMA for urb %p --> %d\n",
                                is_in ? 'R' : 'T', ep->epnum,
                                urb, status);
                        urb->actual_length += dma->actual_len;
                }
        }

        /* turn off DMA requests, discard state, stop polling ... */
        if (is_in) {
                /* giveback saves bulk toggle */
                csr = musb_h_flush_rxfifo(ep, 0);

                /* REVISIT we still get an irq; should likely clear the
                 * endpoint's irq status here to avoid bogus irqs.
                 * clearing that status is platform-specific...
                 */
        } else if (ep->epnum) {
                musb_h_tx_flush_fifo(ep);
                csr = musb_readw(epio, MUSB_TXCSR);
                csr &= ~(MUSB_TXCSR_AUTOSET
                        | MUSB_TXCSR_DMAENAB
                        | MUSB_TXCSR_H_RXSTALL
                        | MUSB_TXCSR_H_NAKTIMEOUT
                        | MUSB_TXCSR_H_ERROR
                        | MUSB_TXCSR_TXPKTRDY);
                musb_writew(epio, MUSB_TXCSR, csr);
                /* REVISIT may need to clear FLUSHFIFO ... */
                musb_writew(epio, MUSB_TXCSR, csr);
                /* flush cpu writebuffer */
                csr = musb_readw(epio, MUSB_TXCSR);
        } else  {
                musb_h_ep0_flush_fifo(ep);
        }
        if (status == 0)
                musb_advance_schedule(ep->musb, urb, ep, is_in);
        return status;
}

static int musb_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
{
        struct musb             *musb = hcd_to_musb(hcd);
        struct musb_qh          *qh;
        unsigned long           flags;
        int                     is_in  = usb_pipein(urb->pipe);
        int                     ret;

        DBG(4, "urb=%p, dev%d ep%d%s\n", urb,
                        usb_pipedevice(urb->pipe),
                        usb_pipeendpoint(urb->pipe),
                        is_in ? "in" : "out");

        spin_lock_irqsave(&musb->lock, flags);
        ret = usb_hcd_check_unlink_urb(hcd, urb, status);
        if (ret)
                goto done;

        qh = urb->hcpriv;
        if (!qh)
                goto done;

        /*
         * Any URB not actively programmed into endpoint hardware can be
         * immediately given back; that's any URB not at the head of an
         * endpoint queue, unless someday we get real DMA queues.  And even
         * if it's at the head, it might not be known to the hardware...
         *
         * Otherwise abort current transfer, pending DMA, etc.; urb->status
         * has already been updated.  This is a synchronous abort; it'd be
         * OK to hold off until after some IRQ, though.
         *
         * NOTE: qh is invalid unless !list_empty(&hep->urb_list)
         */
        if (!qh->is_ready
                        || urb->urb_list.prev != &qh->hep->urb_list
                        || musb_ep_get_qh(qh->hw_ep, is_in) != qh) {
                int     ready = qh->is_ready;

                qh->is_ready = 0;
                musb_giveback(musb, urb, 0);
                qh->is_ready = ready;

                /* If nothing else (usually musb_giveback) is using it
                 * and its URB list has emptied, recycle this qh.
                 */
                if (ready && list_empty(&qh->hep->urb_list)) {
                        qh->hep->hcpriv = NULL;
                        list_del(&qh->ring);
                        kfree(qh);
                }
        } else
                ret = musb_cleanup_urb(urb, qh);
done:
        spin_unlock_irqrestore(&musb->lock, flags);
        return ret;
}

/* disable an endpoint */
static void
musb_h_disable(struct usb_hcd *hcd, struct usb_host_endpoint *hep)
{
        u8                      is_in = hep->desc.bEndpointAddress & USB_DIR_IN;
        unsigned long           flags;
        struct musb             *musb = hcd_to_musb(hcd);
        struct musb_qh          *qh;
        struct urb              *urb;

        spin_lock_irqsave(&musb->lock, flags);

        qh = hep->hcpriv;
        if (qh == NULL)
                goto exit;

        /* NOTE: qh is invalid unless !list_empty(&hep->urb_list) */

        /* Kick the first URB off the hardware, if needed */
        qh->is_ready = 0;
        if (musb_ep_get_qh(qh->hw_ep, is_in) == qh) {
                urb = next_urb(qh);

                /* make software (then hardware) stop ASAP */
                if (!urb->unlinked)
                        urb->status = -ESHUTDOWN;

                /* cleanup */
                musb_cleanup_urb(urb, qh);

                /* Then nuke all the others ... and advance the
                 * queue on hw_ep (e.g. bulk ring) when we're done.
                 */
                while (!list_empty(&hep->urb_list)) {
                        urb = next_urb(qh);
                        urb->status = -ESHUTDOWN;
                        musb_advance_schedule(musb, urb, qh->hw_ep, is_in);
                }
        } else {
                /* Just empty the queue; the hardware is busy with
                 * other transfers, and since !qh->is_ready nothing
                 * will activate any of these as it advances.
                 */
                while (!list_empty(&hep->urb_list))
                        musb_giveback(musb, next_urb(qh), -ESHUTDOWN);

                hep->hcpriv = NULL;
                list_del(&qh->ring);
                kfree(qh);
        }
exit:
        spin_unlock_irqrestore(&musb->lock, flags);
}

static int musb_h_get_frame_number(struct usb_hcd *hcd)
{
        struct musb     *musb = hcd_to_musb(hcd);

        return musb_readw(musb->mregs, MUSB_FRAME);
}

static int musb_h_start(struct usb_hcd *hcd)
{
        struct musb     *musb = hcd_to_musb(hcd);

        /* NOTE: musb_start() is called when the hub driver turns
         * on port power, or when (OTG) peripheral starts.
         */
        hcd->state = HC_STATE_RUNNING;
        musb->port1_status = 0;
        return 0;
}

static void musb_h_stop(struct usb_hcd *hcd)
{
        musb_stop(hcd_to_musb(hcd));
        hcd->state = HC_STATE_HALT;
}

static int musb_bus_suspend(struct usb_hcd *hcd)
{
        struct musb     *musb = hcd_to_musb(hcd);
        u8              devctl;

        if (!is_host_active(musb))
                return 0;

        switch (musb->xceiv->state) {
        case OTG_STATE_A_SUSPEND:
                return 0;
        case OTG_STATE_A_WAIT_VRISE:
                /* ID could be grounded even if there's no device
                 * on the other end of the cable.  NOTE that the
                 * A_WAIT_VRISE timers are messy with MUSB...
                 */
                devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
                if ((devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS)
                        musb->xceiv->state = OTG_STATE_A_WAIT_BCON;
                break;
        default:
                break;
        }

        if (musb->is_active) {
                WARNING("trying to suspend as %s while active\n",
                                otg_state_string(musb));
                return -EBUSY;
        } else
                return 0;
}

static int musb_bus_resume(struct usb_hcd *hcd)
{
        /* resuming child port does the work */
        return 0;
}

const struct hc_driver musb_hc_driver = {
        .description            = "musb-hcd",
        .product_desc           = "MUSB HDRC host driver",
        .hcd_priv_size          = sizeof(struct musb),
        .flags                  = HCD_USB2 | HCD_MEMORY,

        /* not using irq handler or reset hooks from usbcore, since
         * those must be shared with peripheral code for OTG configs
         */

        .start                  = musb_h_start,
        .stop                   = musb_h_stop,

        .get_frame_number       = musb_h_get_frame_number,

        .urb_enqueue            = musb_urb_enqueue,
        .urb_dequeue            = musb_urb_dequeue,
        .endpoint_disable       = musb_h_disable,

        .hub_status_data        = musb_hub_status_data,
        .hub_control            = musb_hub_control,
        .bus_suspend            = musb_bus_suspend,
        .bus_resume             = musb_bus_resume,
        /* .start_port_reset    = NULL, */
        /* .hub_irq_enable      = NULL, */
};