Linux 3.11-rc3

[cris-mirror.git] / drivers / net / can / janz-ican3.c

/*
 * Janz MODULbus VMOD-ICAN3 CAN Interface Driver
 *
 * Copyright (c) 2010 Ira W. Snyder <iws@ovro.caltech.edu>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/platform_device.h>

#include <linux/netdevice.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include <linux/mfd/janz.h>
#include <asm/io.h>

/* the DPM has 64k of memory, organized into 256x 256 byte pages */
#define DPM_NUM_PAGES           256
#define DPM_PAGE_SIZE           256
#define DPM_PAGE_ADDR(p)        ((p) * DPM_PAGE_SIZE)

/* JANZ ICAN3 "old-style" host interface queue page numbers */
#define QUEUE_OLD_CONTROL       0
#define QUEUE_OLD_RB0           1
#define QUEUE_OLD_RB1           2
#define QUEUE_OLD_WB0           3
#define QUEUE_OLD_WB1           4

/* Janz ICAN3 "old-style" host interface control registers */
#define MSYNC_PEER              0x00            /* ICAN only */
#define MSYNC_LOCL              0x01            /* host only */
#define TARGET_RUNNING          0x02

#define MSYNC_RB0               0x01
#define MSYNC_RB1               0x02
#define MSYNC_RBLW              0x04
#define MSYNC_RB_MASK           (MSYNC_RB0 | MSYNC_RB1)

#define MSYNC_WB0               0x10
#define MSYNC_WB1               0x20
#define MSYNC_WBLW              0x40
#define MSYNC_WB_MASK           (MSYNC_WB0 | MSYNC_WB1)

/* Janz ICAN3 "new-style" host interface queue page numbers */
#define QUEUE_TOHOST            5
#define QUEUE_FROMHOST_MID      6
#define QUEUE_FROMHOST_HIGH     7
#define QUEUE_FROMHOST_LOW      8

/* The first free page in the DPM is #9 */
#define DPM_FREE_START          9

/* Janz ICAN3 "new-style" and "fast" host interface descriptor flags */
#define DESC_VALID              0x80
#define DESC_WRAP               0x40
#define DESC_INTERRUPT          0x20
#define DESC_IVALID             0x10
#define DESC_LEN(len)           (len)

/* Janz ICAN3 Firmware Messages */
#define MSG_CONNECTI            0x02
#define MSG_DISCONNECT          0x03
#define MSG_IDVERS              0x04
#define MSG_MSGLOST             0x05
#define MSG_NEWHOSTIF           0x08
#define MSG_INQUIRY             0x0a
#define MSG_SETAFILMASK         0x10
#define MSG_INITFDPMQUEUE       0x11
#define MSG_HWCONF              0x12
#define MSG_FMSGLOST            0x15
#define MSG_CEVTIND             0x37
#define MSG_CBTRREQ             0x41
#define MSG_COFFREQ             0x42
#define MSG_CONREQ              0x43
#define MSG_CCONFREQ            0x47

/*
 * Janz ICAN3 CAN Inquiry Message Types
 *
 * NOTE: there appears to be a firmware bug here. You must send
 * NOTE: INQUIRY_STATUS and expect to receive an INQUIRY_EXTENDED
 * NOTE: response. The controller never responds to a message with
 * NOTE: the INQUIRY_EXTENDED subspec :(
 */
#define INQUIRY_STATUS          0x00
#define INQUIRY_TERMINATION     0x01
#define INQUIRY_EXTENDED        0x04

/* Janz ICAN3 CAN Set Acceptance Filter Mask Message Types */
#define SETAFILMASK_REJECT      0x00
#define SETAFILMASK_FASTIF      0x02

/* Janz ICAN3 CAN Hardware Configuration Message Types */
#define HWCONF_TERMINATE_ON     0x01
#define HWCONF_TERMINATE_OFF    0x00

/* Janz ICAN3 CAN Event Indication Message Types */
#define CEVTIND_EI              0x01
#define CEVTIND_DOI             0x02
#define CEVTIND_LOST            0x04
#define CEVTIND_FULL            0x08
#define CEVTIND_BEI             0x10

#define CEVTIND_CHIP_SJA1000    0x02

#define ICAN3_BUSERR_QUOTA_MAX  255

/* Janz ICAN3 CAN Frame Conversion */
#define ICAN3_SNGL      0x02
#define ICAN3_ECHO      0x10
#define ICAN3_EFF_RTR   0x40
#define ICAN3_SFF_RTR   0x10
#define ICAN3_EFF       0x80

#define ICAN3_CAN_TYPE_MASK     0x0f
#define ICAN3_CAN_TYPE_SFF      0x00
#define ICAN3_CAN_TYPE_EFF      0x01

#define ICAN3_CAN_DLC_MASK      0x0f

/*
 * SJA1000 Status and Error Register Definitions
 *
 * Copied from drivers/net/can/sja1000/sja1000.h
 */

/* status register content */
#define SR_BS           0x80
#define SR_ES           0x40
#define SR_TS           0x20
#define SR_RS           0x10
#define SR_TCS          0x08
#define SR_TBS          0x04
#define SR_DOS          0x02
#define SR_RBS          0x01

#define SR_CRIT (SR_BS|SR_ES)

/* ECC register */
#define ECC_SEG         0x1F
#define ECC_DIR         0x20
#define ECC_ERR         6
#define ECC_BIT         0x00
#define ECC_FORM        0x40
#define ECC_STUFF       0x80
#define ECC_MASK        0xc0

/* Number of buffers for use in the "new-style" host interface */
#define ICAN3_NEW_BUFFERS       16

/* Number of buffers for use in the "fast" host interface */
#define ICAN3_TX_BUFFERS        512
#define ICAN3_RX_BUFFERS        1024

/* SJA1000 Clock Input */
#define ICAN3_CAN_CLOCK         8000000

/* Driver Name */
#define DRV_NAME "janz-ican3"

/* DPM Control Registers -- starts at offset 0x100 in the MODULbus registers */
struct ican3_dpm_control {
        /* window address register */
        u8 window_address;
        u8 unused1;

        /*
         * Read access: clear interrupt from microcontroller
         * Write access: send interrupt to microcontroller
         */
        u8 interrupt;
        u8 unused2;

        /* write-only: reset all hardware on the module */
        u8 hwreset;
        u8 unused3;

        /* write-only: generate an interrupt to the TPU */
        u8 tpuinterrupt;
};

struct ican3_dev {

        /* must be the first member */
        struct can_priv can;

        /* CAN network device */
        struct net_device *ndev;
        struct napi_struct napi;

        /* Device for printing */
        struct device *dev;

        /* module number */
        unsigned int num;

        /* base address of registers and IRQ */
        struct janz_cmodio_onboard_regs __iomem *ctrl;
        struct ican3_dpm_control __iomem *dpmctrl;
        void __iomem *dpm;
        int irq;

        /* CAN bus termination status */
        struct completion termination_comp;
        bool termination_enabled;

        /* CAN bus error status registers */
        struct completion buserror_comp;
        struct can_berr_counter bec;

        /* old and new style host interface */
        unsigned int iftype;

        /* queue for echo packets */
        struct sk_buff_head echoq;

        /*
         * Any function which changes the current DPM page must hold this
         * lock while it is performing data accesses. This ensures that the
         * function will not be preempted and end up reading data from a
         * different DPM page than it expects.
         */
        spinlock_t lock;

        /* new host interface */
        unsigned int rx_int;
        unsigned int rx_num;
        unsigned int tx_num;

        /* fast host interface */
        unsigned int fastrx_start;
        unsigned int fastrx_num;
        unsigned int fasttx_start;
        unsigned int fasttx_num;

        /* first free DPM page */
        unsigned int free_page;
};

struct ican3_msg {
        u8 control;
        u8 spec;
        __le16 len;
        u8 data[252];
};

struct ican3_new_desc {
        u8 control;
        u8 pointer;
};

struct ican3_fast_desc {
        u8 control;
        u8 command;
        u8 data[14];
};

/* write to the window basic address register */
static inline void ican3_set_page(struct ican3_dev *mod, unsigned int page)
{
        BUG_ON(page >= DPM_NUM_PAGES);
        iowrite8(page, &mod->dpmctrl->window_address);
}

/*
 * ICAN3 "old-style" host interface
 */

/*
 * Receive a message from the ICAN3 "old-style" firmware interface
 *
 * LOCKING: must hold mod->lock
 *
 * returns 0 on success, -ENOMEM when no message exists
 */
static int ican3_old_recv_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        unsigned int mbox, mbox_page;
        u8 locl, peer, xord;

        /* get the MSYNC registers */
        ican3_set_page(mod, QUEUE_OLD_CONTROL);
        peer = ioread8(mod->dpm + MSYNC_PEER);
        locl = ioread8(mod->dpm + MSYNC_LOCL);
        xord = locl ^ peer;

        if ((xord & MSYNC_RB_MASK) == 0x00) {
                dev_dbg(mod->dev, "no mbox for reading\n");
                return -ENOMEM;
        }

        /* find the first free mbox to read */
        if ((xord & MSYNC_RB_MASK) == MSYNC_RB_MASK)
                mbox = (xord & MSYNC_RBLW) ? MSYNC_RB0 : MSYNC_RB1;
        else
                mbox = (xord & MSYNC_RB0) ? MSYNC_RB0 : MSYNC_RB1;

        /* copy the message */
        mbox_page = (mbox == MSYNC_RB0) ? QUEUE_OLD_RB0 : QUEUE_OLD_RB1;
        ican3_set_page(mod, mbox_page);
        memcpy_fromio(msg, mod->dpm, sizeof(*msg));

        /*
         * notify the firmware that the read buffer is available
         * for it to fill again
         */
        locl ^= mbox;

        ican3_set_page(mod, QUEUE_OLD_CONTROL);
        iowrite8(locl, mod->dpm + MSYNC_LOCL);
        return 0;
}

/*
 * Send a message through the "old-style" firmware interface
 *
 * LOCKING: must hold mod->lock
 *
 * returns 0 on success, -ENOMEM when no free space exists
 */
static int ican3_old_send_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        unsigned int mbox, mbox_page;
        u8 locl, peer, xord;

        /* get the MSYNC registers */
        ican3_set_page(mod, QUEUE_OLD_CONTROL);
        peer = ioread8(mod->dpm + MSYNC_PEER);
        locl = ioread8(mod->dpm + MSYNC_LOCL);
        xord = locl ^ peer;

        if ((xord & MSYNC_WB_MASK) == MSYNC_WB_MASK) {
                dev_err(mod->dev, "no mbox for writing\n");
                return -ENOMEM;
        }

        /* calculate a free mbox to use */
        mbox = (xord & MSYNC_WB0) ? MSYNC_WB1 : MSYNC_WB0;

        /* copy the message to the DPM */
        mbox_page = (mbox == MSYNC_WB0) ? QUEUE_OLD_WB0 : QUEUE_OLD_WB1;
        ican3_set_page(mod, mbox_page);
        memcpy_toio(mod->dpm, msg, sizeof(*msg));

        locl ^= mbox;
        if (mbox == MSYNC_WB1)
                locl |= MSYNC_WBLW;

        ican3_set_page(mod, QUEUE_OLD_CONTROL);
        iowrite8(locl, mod->dpm + MSYNC_LOCL);
        return 0;
}

/*
 * ICAN3 "new-style" Host Interface Setup
 */

static void ican3_init_new_host_interface(struct ican3_dev *mod)
{
        struct ican3_new_desc desc;
        unsigned long flags;
        void __iomem *dst;
        int i;

        spin_lock_irqsave(&mod->lock, flags);

        /* setup the internal datastructures for RX */
        mod->rx_num = 0;
        mod->rx_int = 0;

        /* tohost queue descriptors are in page 5 */
        ican3_set_page(mod, QUEUE_TOHOST);
        dst = mod->dpm;

        /* initialize the tohost (rx) queue descriptors: pages 9-24 */
        for (i = 0; i < ICAN3_NEW_BUFFERS; i++) {
                desc.control = DESC_INTERRUPT | DESC_LEN(1); /* I L=1 */
                desc.pointer = mod->free_page;

                /* set wrap flag on last buffer */
                if (i == ICAN3_NEW_BUFFERS - 1)
                        desc.control |= DESC_WRAP;

                memcpy_toio(dst, &desc, sizeof(desc));
                dst += sizeof(desc);
                mod->free_page++;
        }

        /* fromhost (tx) mid queue descriptors are in page 6 */
        ican3_set_page(mod, QUEUE_FROMHOST_MID);
        dst = mod->dpm;

        /* setup the internal datastructures for TX */
        mod->tx_num = 0;

        /* initialize the fromhost mid queue descriptors: pages 25-40 */
        for (i = 0; i < ICAN3_NEW_BUFFERS; i++) {
                desc.control = DESC_VALID | DESC_LEN(1); /* V L=1 */
                desc.pointer = mod->free_page;

                /* set wrap flag on last buffer */
                if (i == ICAN3_NEW_BUFFERS - 1)
                        desc.control |= DESC_WRAP;

                memcpy_toio(dst, &desc, sizeof(desc));
                dst += sizeof(desc);
                mod->free_page++;
        }

        /* fromhost hi queue descriptors are in page 7 */
        ican3_set_page(mod, QUEUE_FROMHOST_HIGH);
        dst = mod->dpm;

        /* initialize only a single buffer in the fromhost hi queue (unused) */
        desc.control = DESC_VALID | DESC_WRAP | DESC_LEN(1); /* VW L=1 */
        desc.pointer = mod->free_page;
        memcpy_toio(dst, &desc, sizeof(desc));
        mod->free_page++;

        /* fromhost low queue descriptors are in page 8 */
        ican3_set_page(mod, QUEUE_FROMHOST_LOW);
        dst = mod->dpm;

        /* initialize only a single buffer in the fromhost low queue (unused) */
        desc.control = DESC_VALID | DESC_WRAP | DESC_LEN(1); /* VW L=1 */
        desc.pointer = mod->free_page;
        memcpy_toio(dst, &desc, sizeof(desc));
        mod->free_page++;

        spin_unlock_irqrestore(&mod->lock, flags);
}

/*
 * ICAN3 Fast Host Interface Setup
 */

static void ican3_init_fast_host_interface(struct ican3_dev *mod)
{
        struct ican3_fast_desc desc;
        unsigned long flags;
        unsigned int addr;
        void __iomem *dst;
        int i;

        spin_lock_irqsave(&mod->lock, flags);

        /* save the start recv page */
        mod->fastrx_start = mod->free_page;
        mod->fastrx_num = 0;

        /* build a single fast tohost queue descriptor */
        memset(&desc, 0, sizeof(desc));
        desc.control = 0x00;
        desc.command = 1;

        /* build the tohost queue descriptor ring in memory */
        addr = 0;
        for (i = 0; i < ICAN3_RX_BUFFERS; i++) {

                /* set the wrap bit on the last buffer */
                if (i == ICAN3_RX_BUFFERS - 1)
                        desc.control |= DESC_WRAP;

                /* switch to the correct page */
                ican3_set_page(mod, mod->free_page);

                /* copy the descriptor to the DPM */
                dst = mod->dpm + addr;
                memcpy_toio(dst, &desc, sizeof(desc));
                addr += sizeof(desc);

                /* move to the next page if necessary */
                if (addr >= DPM_PAGE_SIZE) {
                        addr = 0;
                        mod->free_page++;
                }
        }

        /* make sure we page-align the next queue */
        if (addr != 0)
                mod->free_page++;

        /* save the start xmit page */
        mod->fasttx_start = mod->free_page;
        mod->fasttx_num = 0;

        /* build a single fast fromhost queue descriptor */
        memset(&desc, 0, sizeof(desc));
        desc.control = DESC_VALID;
        desc.command = 1;

        /* build the fromhost queue descriptor ring in memory */
        addr = 0;
        for (i = 0; i < ICAN3_TX_BUFFERS; i++) {

                /* set the wrap bit on the last buffer */
                if (i == ICAN3_TX_BUFFERS - 1)
                        desc.control |= DESC_WRAP;

                /* switch to the correct page */
                ican3_set_page(mod, mod->free_page);

                /* copy the descriptor to the DPM */
                dst = mod->dpm + addr;
                memcpy_toio(dst, &desc, sizeof(desc));
                addr += sizeof(desc);

                /* move to the next page if necessary */
                if (addr >= DPM_PAGE_SIZE) {
                        addr = 0;
                        mod->free_page++;
                }
        }

        spin_unlock_irqrestore(&mod->lock, flags);
}

/*
 * ICAN3 "new-style" Host Interface Message Helpers
 */

/*
 * LOCKING: must hold mod->lock
 */
static int ican3_new_send_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        struct ican3_new_desc desc;
        void __iomem *desc_addr = mod->dpm + (mod->tx_num * sizeof(desc));

        /* switch to the fromhost mid queue, and read the buffer descriptor */
        ican3_set_page(mod, QUEUE_FROMHOST_MID);
        memcpy_fromio(&desc, desc_addr, sizeof(desc));

        if (!(desc.control & DESC_VALID)) {
                dev_dbg(mod->dev, "%s: no free buffers\n", __func__);
                return -ENOMEM;
        }

        /* switch to the data page, copy the data */
        ican3_set_page(mod, desc.pointer);
        memcpy_toio(mod->dpm, msg, sizeof(*msg));

        /* switch back to the descriptor, set the valid bit, write it back */
        ican3_set_page(mod, QUEUE_FROMHOST_MID);
        desc.control ^= DESC_VALID;
        memcpy_toio(desc_addr, &desc, sizeof(desc));

        /* update the tx number */
        mod->tx_num = (desc.control & DESC_WRAP) ? 0 : (mod->tx_num + 1);
        return 0;
}

/*
 * LOCKING: must hold mod->lock
 */
static int ican3_new_recv_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        struct ican3_new_desc desc;
        void __iomem *desc_addr = mod->dpm + (mod->rx_num * sizeof(desc));

        /* switch to the tohost queue, and read the buffer descriptor */
        ican3_set_page(mod, QUEUE_TOHOST);
        memcpy_fromio(&desc, desc_addr, sizeof(desc));

        if (!(desc.control & DESC_VALID)) {
                dev_dbg(mod->dev, "%s: no buffers to recv\n", __func__);
                return -ENOMEM;
        }

        /* switch to the data page, copy the data */
        ican3_set_page(mod, desc.pointer);
        memcpy_fromio(msg, mod->dpm, sizeof(*msg));

        /* switch back to the descriptor, toggle the valid bit, write it back */
        ican3_set_page(mod, QUEUE_TOHOST);
        desc.control ^= DESC_VALID;
        memcpy_toio(desc_addr, &desc, sizeof(desc));

        /* update the rx number */
        mod->rx_num = (desc.control & DESC_WRAP) ? 0 : (mod->rx_num + 1);
        return 0;
}

/*
 * Message Send / Recv Helpers
 */

static int ican3_send_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&mod->lock, flags);

        if (mod->iftype == 0)
                ret = ican3_old_send_msg(mod, msg);
        else
                ret = ican3_new_send_msg(mod, msg);

        spin_unlock_irqrestore(&mod->lock, flags);
        return ret;
}

static int ican3_recv_msg(struct ican3_dev *mod, struct ican3_msg *msg)
{
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&mod->lock, flags);

        if (mod->iftype == 0)
                ret = ican3_old_recv_msg(mod, msg);
        else
                ret = ican3_new_recv_msg(mod, msg);

        spin_unlock_irqrestore(&mod->lock, flags);
        return ret;
}

/*
 * Quick Pre-constructed Messages
 */

static int ican3_msg_connect(struct ican3_dev *mod)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_CONNECTI;
        msg.len = cpu_to_le16(0);

        return ican3_send_msg(mod, &msg);
}

static int ican3_msg_disconnect(struct ican3_dev *mod)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_DISCONNECT;
        msg.len = cpu_to_le16(0);

        return ican3_send_msg(mod, &msg);
}

static int ican3_msg_newhostif(struct ican3_dev *mod)
{
        struct ican3_msg msg;
        int ret;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_NEWHOSTIF;
        msg.len = cpu_to_le16(0);

        /* If we're not using the old interface, switching seems bogus */
        WARN_ON(mod->iftype != 0);

        ret = ican3_send_msg(mod, &msg);
        if (ret)
                return ret;

        /* mark the module as using the new host interface */
        mod->iftype = 1;
        return 0;
}

static int ican3_msg_fasthostif(struct ican3_dev *mod)
{
        struct ican3_msg msg;
        unsigned int addr;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_INITFDPMQUEUE;
        msg.len = cpu_to_le16(8);

        /* write the tohost queue start address */
        addr = DPM_PAGE_ADDR(mod->fastrx_start);
        msg.data[0] = addr & 0xff;
        msg.data[1] = (addr >> 8) & 0xff;
        msg.data[2] = (addr >> 16) & 0xff;
        msg.data[3] = (addr >> 24) & 0xff;

        /* write the fromhost queue start address */
        addr = DPM_PAGE_ADDR(mod->fasttx_start);
        msg.data[4] = addr & 0xff;
        msg.data[5] = (addr >> 8) & 0xff;
        msg.data[6] = (addr >> 16) & 0xff;
        msg.data[7] = (addr >> 24) & 0xff;

        /* If we're not using the new interface yet, we cannot do this */
        WARN_ON(mod->iftype != 1);

        return ican3_send_msg(mod, &msg);
}

/*
 * Setup the CAN filter to either accept or reject all
 * messages from the CAN bus.
 */
static int ican3_set_id_filter(struct ican3_dev *mod, bool accept)
{
        struct ican3_msg msg;
        int ret;

        /* Standard Frame Format */
        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_SETAFILMASK;
        msg.len = cpu_to_le16(5);
        msg.data[0] = 0x00; /* IDLo LSB */
        msg.data[1] = 0x00; /* IDLo MSB */
        msg.data[2] = 0xff; /* IDHi LSB */
        msg.data[3] = 0x07; /* IDHi MSB */

        /* accept all frames for fast host if, or reject all frames */
        msg.data[4] = accept ? SETAFILMASK_FASTIF : SETAFILMASK_REJECT;

        ret = ican3_send_msg(mod, &msg);
        if (ret)
                return ret;

        /* Extended Frame Format */
        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_SETAFILMASK;
        msg.len = cpu_to_le16(13);
        msg.data[0] = 0;    /* MUX = 0 */
        msg.data[1] = 0x00; /* IDLo LSB */
        msg.data[2] = 0x00;
        msg.data[3] = 0x00;
        msg.data[4] = 0x20; /* IDLo MSB */
        msg.data[5] = 0xff; /* IDHi LSB */
        msg.data[6] = 0xff;
        msg.data[7] = 0xff;
        msg.data[8] = 0x3f; /* IDHi MSB */

        /* accept all frames for fast host if, or reject all frames */
        msg.data[9] = accept ? SETAFILMASK_FASTIF : SETAFILMASK_REJECT;

        return ican3_send_msg(mod, &msg);
}

/*
 * Bring the CAN bus online or offline
 */
static int ican3_set_bus_state(struct ican3_dev *mod, bool on)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = on ? MSG_CONREQ : MSG_COFFREQ;
        msg.len = cpu_to_le16(0);

        return ican3_send_msg(mod, &msg);
}

static int ican3_set_termination(struct ican3_dev *mod, bool on)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_HWCONF;
        msg.len = cpu_to_le16(2);
        msg.data[0] = 0x00;
        msg.data[1] = on ? HWCONF_TERMINATE_ON : HWCONF_TERMINATE_OFF;

        return ican3_send_msg(mod, &msg);
}

static int ican3_send_inquiry(struct ican3_dev *mod, u8 subspec)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_INQUIRY;
        msg.len = cpu_to_le16(2);
        msg.data[0] = subspec;
        msg.data[1] = 0x00;

        return ican3_send_msg(mod, &msg);
}

static int ican3_set_buserror(struct ican3_dev *mod, u8 quota)
{
        struct ican3_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_CCONFREQ;
        msg.len = cpu_to_le16(2);
        msg.data[0] = 0x00;
        msg.data[1] = quota;

        return ican3_send_msg(mod, &msg);
}

/*
 * ICAN3 to Linux CAN Frame Conversion
 */

static void ican3_to_can_frame(struct ican3_dev *mod,
                               struct ican3_fast_desc *desc,
                               struct can_frame *cf)
{
        if ((desc->command & ICAN3_CAN_TYPE_MASK) == ICAN3_CAN_TYPE_SFF) {
                if (desc->data[1] & ICAN3_SFF_RTR)
                        cf->can_id |= CAN_RTR_FLAG;

                cf->can_id |= desc->data[0] << 3;
                cf->can_id |= (desc->data[1] & 0xe0) >> 5;
                cf->can_dlc = get_can_dlc(desc->data[1] & ICAN3_CAN_DLC_MASK);
                memcpy(cf->data, &desc->data[2], cf->can_dlc);
        } else {
                cf->can_dlc = get_can_dlc(desc->data[0] & ICAN3_CAN_DLC_MASK);
                if (desc->data[0] & ICAN3_EFF_RTR)
                        cf->can_id |= CAN_RTR_FLAG;

                if (desc->data[0] & ICAN3_EFF) {
                        cf->can_id |= CAN_EFF_FLAG;
                        cf->can_id |= desc->data[2] << 21; /* 28-21 */
                        cf->can_id |= desc->data[3] << 13; /* 20-13 */
                        cf->can_id |= desc->data[4] << 5;  /* 12-5  */
                        cf->can_id |= (desc->data[5] & 0xf8) >> 3;
                } else {
                        cf->can_id |= desc->data[2] << 3;  /* 10-3  */
                        cf->can_id |= desc->data[3] >> 5;  /* 2-0   */
                }

                memcpy(cf->data, &desc->data[6], cf->can_dlc);
        }
}

static void can_frame_to_ican3(struct ican3_dev *mod,
                               struct can_frame *cf,
                               struct ican3_fast_desc *desc)
{
        /* clear out any stale data in the descriptor */
        memset(desc->data, 0, sizeof(desc->data));

        /* we always use the extended format, with the ECHO flag set */
        desc->command = ICAN3_CAN_TYPE_EFF;
        desc->data[0] |= cf->can_dlc;
        desc->data[1] |= ICAN3_ECHO;

        /* support single transmission (no retries) mode */
        if (mod->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT)
                desc->data[1] |= ICAN3_SNGL;

        if (cf->can_id & CAN_RTR_FLAG)
                desc->data[0] |= ICAN3_EFF_RTR;

        /* pack the id into the correct places */
        if (cf->can_id & CAN_EFF_FLAG) {
                desc->data[0] |= ICAN3_EFF;
                desc->data[2] = (cf->can_id & 0x1fe00000) >> 21; /* 28-21 */
                desc->data[3] = (cf->can_id & 0x001fe000) >> 13; /* 20-13 */
                desc->data[4] = (cf->can_id & 0x00001fe0) >> 5;  /* 12-5  */
                desc->data[5] = (cf->can_id & 0x0000001f) << 3;  /* 4-0   */
        } else {
                desc->data[2] = (cf->can_id & 0x7F8) >> 3; /* bits 10-3 */
                desc->data[3] = (cf->can_id & 0x007) << 5; /* bits 2-0  */
        }

        /* copy the data bits into the descriptor */
        memcpy(&desc->data[6], cf->data, cf->can_dlc);
}

/*
 * Interrupt Handling
 */

/*
 * Handle an ID + Version message response from the firmware. We never generate
 * this message in production code, but it is very useful when debugging to be
 * able to display this message.
 */
static void ican3_handle_idvers(struct ican3_dev *mod, struct ican3_msg *msg)
{
        dev_dbg(mod->dev, "IDVERS response: %s\n", msg->data);
}

static void ican3_handle_msglost(struct ican3_dev *mod, struct ican3_msg *msg)
{
        struct net_device *dev = mod->ndev;
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;

        /*
         * Report that communication messages with the microcontroller firmware
         * are being lost. These are never CAN frames, so we do not generate an
         * error frame for userspace
         */
        if (msg->spec == MSG_MSGLOST) {
                dev_err(mod->dev, "lost %d control messages\n", msg->data[0]);
                return;
        }

        /*
         * Oops, this indicates that we have lost messages in the fast queue,
         * which are exclusively CAN messages. Our driver isn't reading CAN
         * frames fast enough.
         *
         * We'll pretend that the SJA1000 told us that it ran out of buffer
         * space, because there is not a better message for this.
         */
        skb = alloc_can_err_skb(dev, &cf);
        if (skb) {
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                stats->rx_over_errors++;
                stats->rx_errors++;
                netif_rx(skb);
        }
}

/*
 * Handle CAN Event Indication Messages from the firmware
 *
 * The ICAN3 firmware provides the values of some SJA1000 registers when it
 * generates this message. The code below is largely copied from the
 * drivers/net/can/sja1000/sja1000.c file, and adapted as necessary
 */
static int ican3_handle_cevtind(struct ican3_dev *mod, struct ican3_msg *msg)
{
        struct net_device *dev = mod->ndev;
        struct net_device_stats *stats = &dev->stats;
        enum can_state state = mod->can.state;
        u8 isrc, ecc, status, rxerr, txerr;
        struct can_frame *cf;
        struct sk_buff *skb;

        /* we can only handle the SJA1000 part */
        if (msg->data[1] != CEVTIND_CHIP_SJA1000) {
                dev_err(mod->dev, "unable to handle errors on non-SJA1000\n");
                return -ENODEV;
        }

        /* check the message length for sanity */
        if (le16_to_cpu(msg->len) < 6) {
                dev_err(mod->dev, "error message too short\n");
                return -EINVAL;
        }

        isrc = msg->data[0];
        ecc = msg->data[2];
        status = msg->data[3];
        rxerr = msg->data[4];
        txerr = msg->data[5];

        /*
         * This hardware lacks any support other than bus error messages to
         * determine if packet transmission has failed.
         *
         * When TX errors happen, one echo skb needs to be dropped from the
         * front of the queue.
         *
         * A small bit of code is duplicated here and below, to avoid error
         * skb allocation when it will just be freed immediately.
         */
        if (isrc == CEVTIND_BEI) {
                int ret;
                dev_dbg(mod->dev, "bus error interrupt\n");

                /* TX error */
                if (!(ecc & ECC_DIR)) {
                        kfree_skb(skb_dequeue(&mod->echoq));
                        stats->tx_errors++;
                } else {
                        stats->rx_errors++;
                }

                /*
                 * The controller automatically disables bus-error interrupts
                 * and therefore we must re-enable them.
                 */
                ret = ican3_set_buserror(mod, 1);
                if (ret) {
                        dev_err(mod->dev, "unable to re-enable bus-error\n");
                        return ret;
                }

                /* bus error reporting is off, return immediately */
                if (!(mod->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING))
                        return 0;
        }

        skb = alloc_can_err_skb(dev, &cf);
        if (skb == NULL)
                return -ENOMEM;

        /* data overrun interrupt */
        if (isrc == CEVTIND_DOI || isrc == CEVTIND_LOST) {
                dev_dbg(mod->dev, "data overrun interrupt\n");
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                stats->rx_over_errors++;
                stats->rx_errors++;
        }

        /* error warning + passive interrupt */
        if (isrc == CEVTIND_EI) {
                dev_dbg(mod->dev, "error warning + passive interrupt\n");
                if (status & SR_BS) {
                        state = CAN_STATE_BUS_OFF;
                        cf->can_id |= CAN_ERR_BUSOFF;
                        can_bus_off(dev);
                } else if (status & SR_ES) {
                        if (rxerr >= 128 || txerr >= 128)
                                state = CAN_STATE_ERROR_PASSIVE;
                        else
                                state = CAN_STATE_ERROR_WARNING;
                } else {
                        state = CAN_STATE_ERROR_ACTIVE;
                }
        }

        /* bus error interrupt */
        if (isrc == CEVTIND_BEI) {
                mod->can.can_stats.bus_error++;
                cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;

                switch (ecc & ECC_MASK) {
                case ECC_BIT:
                        cf->data[2] |= CAN_ERR_PROT_BIT;
                        break;
                case ECC_FORM:
                        cf->data[2] |= CAN_ERR_PROT_FORM;
                        break;
                case ECC_STUFF:
                        cf->data[2] |= CAN_ERR_PROT_STUFF;
                        break;
                default:
                        cf->data[2] |= CAN_ERR_PROT_UNSPEC;
                        cf->data[3] = ecc & ECC_SEG;
                        break;
                }

                if (!(ecc & ECC_DIR))
                        cf->data[2] |= CAN_ERR_PROT_TX;

                cf->data[6] = txerr;
                cf->data[7] = rxerr;
        }

        if (state != mod->can.state && (state == CAN_STATE_ERROR_WARNING ||
                                        state == CAN_STATE_ERROR_PASSIVE)) {
                cf->can_id |= CAN_ERR_CRTL;
                if (state == CAN_STATE_ERROR_WARNING) {
                        mod->can.can_stats.error_warning++;
                        cf->data[1] = (txerr > rxerr) ?
                                CAN_ERR_CRTL_TX_WARNING :
                                CAN_ERR_CRTL_RX_WARNING;
                } else {
                        mod->can.can_stats.error_passive++;
                        cf->data[1] = (txerr > rxerr) ?
                                CAN_ERR_CRTL_TX_PASSIVE :
                                CAN_ERR_CRTL_RX_PASSIVE;
                }

                cf->data[6] = txerr;
                cf->data[7] = rxerr;
        }

        mod->can.state = state;
        netif_rx(skb);
        return 0;
}

static void ican3_handle_inquiry(struct ican3_dev *mod, struct ican3_msg *msg)
{
        switch (msg->data[0]) {
        case INQUIRY_STATUS:
        case INQUIRY_EXTENDED:
                mod->bec.rxerr = msg->data[5];
                mod->bec.txerr = msg->data[6];
                complete(&mod->buserror_comp);
                break;
        case INQUIRY_TERMINATION:
                mod->termination_enabled = msg->data[6] & HWCONF_TERMINATE_ON;
                complete(&mod->termination_comp);
                break;
        default:
                dev_err(mod->dev, "received an unknown inquiry response\n");
                break;
        }
}

static void ican3_handle_unknown_message(struct ican3_dev *mod,
                                        struct ican3_msg *msg)
{
        dev_warn(mod->dev, "received unknown message: spec 0x%.2x length %d\n",
                           msg->spec, le16_to_cpu(msg->len));
}

/*
 * Handle a control message from the firmware
 */
static void ican3_handle_message(struct ican3_dev *mod, struct ican3_msg *msg)
{
        dev_dbg(mod->dev, "%s: modno %d spec 0x%.2x len %d bytes\n", __func__,
                           mod->num, msg->spec, le16_to_cpu(msg->len));

        switch (msg->spec) {
        case MSG_IDVERS:
                ican3_handle_idvers(mod, msg);
                break;
        case MSG_MSGLOST:
        case MSG_FMSGLOST:
                ican3_handle_msglost(mod, msg);
                break;
        case MSG_CEVTIND:
                ican3_handle_cevtind(mod, msg);
                break;
        case MSG_INQUIRY:
                ican3_handle_inquiry(mod, msg);
                break;
        default:
                ican3_handle_unknown_message(mod, msg);
                break;
        }
}

/*
 * The ican3 needs to store all echo skbs, and therefore cannot
 * use the generic infrastructure for this.
 */
static void ican3_put_echo_skb(struct ican3_dev *mod, struct sk_buff *skb)
{
        struct sock *srcsk = skb->sk;

        if (atomic_read(&skb->users) != 1) {
                struct sk_buff *old_skb = skb;

                skb = skb_clone(old_skb, GFP_ATOMIC);
                kfree_skb(old_skb);
                if (!skb)
                        return;
        } else {
                skb_orphan(skb);
        }

        skb->sk = srcsk;

        /* save this skb for tx interrupt echo handling */
        skb_queue_tail(&mod->echoq, skb);
}

static unsigned int ican3_get_echo_skb(struct ican3_dev *mod)
{
        struct sk_buff *skb = skb_dequeue(&mod->echoq);
        struct can_frame *cf;
        u8 dlc;

        /* this should never trigger unless there is a driver bug */
        if (!skb) {
                netdev_err(mod->ndev, "BUG: echo skb not occupied\n");
                return 0;
        }

        cf = (struct can_frame *)skb->data;
        dlc = cf->can_dlc;

        /* check flag whether this packet has to be looped back */
        if (skb->pkt_type != PACKET_LOOPBACK) {
                kfree_skb(skb);
                return dlc;
        }

        skb->protocol = htons(ETH_P_CAN);
        skb->pkt_type = PACKET_BROADCAST;
        skb->ip_summed = CHECKSUM_UNNECESSARY;
        skb->dev = mod->ndev;
        netif_receive_skb(skb);
        return dlc;
}

/*
 * Compare an skb with an existing echo skb
 *
 * This function will be used on devices which have a hardware loopback.
 * On these devices, this function can be used to compare a received skb
 * with the saved echo skbs so that the hardware echo skb can be dropped.
 *
 * Returns true if the skb's are identical, false otherwise.
 */
static bool ican3_echo_skb_matches(struct ican3_dev *mod, struct sk_buff *skb)
{
        struct can_frame *cf = (struct can_frame *)skb->data;
        struct sk_buff *echo_skb = skb_peek(&mod->echoq);
        struct can_frame *echo_cf;

        if (!echo_skb)
                return false;

        echo_cf = (struct can_frame *)echo_skb->data;
        if (cf->can_id != echo_cf->can_id)
                return false;

        if (cf->can_dlc != echo_cf->can_dlc)
                return false;

        return memcmp(cf->data, echo_cf->data, cf->can_dlc) == 0;
}

/*
 * Check that there is room in the TX ring to transmit another skb
 *
 * LOCKING: must hold mod->lock
 */
static bool ican3_txok(struct ican3_dev *mod)
{
        struct ican3_fast_desc __iomem *desc;
        u8 control;

        /* check that we have echo queue space */
        if (skb_queue_len(&mod->echoq) >= ICAN3_TX_BUFFERS)
                return false;

        /* copy the control bits of the descriptor */
        ican3_set_page(mod, mod->fasttx_start + (mod->fasttx_num / 16));
        desc = mod->dpm + ((mod->fasttx_num % 16) * sizeof(*desc));
        control = ioread8(&desc->control);

        /* if the control bits are not valid, then we have no more space */
        if (!(control & DESC_VALID))
                return false;

        return true;
}

/*
 * Receive one CAN frame from the hardware
 *
 * CONTEXT: must be called from user context
 */
static int ican3_recv_skb(struct ican3_dev *mod)
{
        struct net_device *ndev = mod->ndev;
        struct net_device_stats *stats = &ndev->stats;
        struct ican3_fast_desc desc;
        void __iomem *desc_addr;
        struct can_frame *cf;
        struct sk_buff *skb;
        unsigned long flags;

        spin_lock_irqsave(&mod->lock, flags);

        /* copy the whole descriptor */
        ican3_set_page(mod, mod->fastrx_start + (mod->fastrx_num / 16));
        desc_addr = mod->dpm + ((mod->fastrx_num % 16) * sizeof(desc));
        memcpy_fromio(&desc, desc_addr, sizeof(desc));

        spin_unlock_irqrestore(&mod->lock, flags);

        /* check that we actually have a CAN frame */
        if (!(desc.control & DESC_VALID))
                return -ENOBUFS;

        /* allocate an skb */
        skb = alloc_can_skb(ndev, &cf);
        if (unlikely(skb == NULL)) {
                stats->rx_dropped++;
                goto err_noalloc;
        }

        /* convert the ICAN3 frame into Linux CAN format */
        ican3_to_can_frame(mod, &desc, cf);

        /*
         * If this is an ECHO frame received from the hardware loopback
         * feature, use the skb saved in the ECHO stack instead. This allows
         * the Linux CAN core to support CAN_RAW_RECV_OWN_MSGS correctly.
         *
         * Since this is a confirmation of a successfully transmitted packet
         * sent from this host, update the transmit statistics.
         *
         * Also, the netdevice queue needs to be allowed to send packets again.
         */
        if (ican3_echo_skb_matches(mod, skb)) {
                stats->tx_packets++;
                stats->tx_bytes += ican3_get_echo_skb(mod);
                kfree_skb(skb);
                goto err_noalloc;
        }

        /* update statistics, receive the skb */
        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;
        netif_receive_skb(skb);

err_noalloc:
        /* toggle the valid bit and return the descriptor to the ring */
        desc.control ^= DESC_VALID;

        spin_lock_irqsave(&mod->lock, flags);

        ican3_set_page(mod, mod->fastrx_start + (mod->fastrx_num / 16));
        memcpy_toio(desc_addr, &desc, 1);

        /* update the next buffer pointer */
        mod->fastrx_num = (desc.control & DESC_WRAP) ? 0
                                                     : (mod->fastrx_num + 1);

        /* there are still more buffers to process */
        spin_unlock_irqrestore(&mod->lock, flags);
        return 0;
}

static int ican3_napi(struct napi_struct *napi, int budget)
{
        struct ican3_dev *mod = container_of(napi, struct ican3_dev, napi);
        unsigned long flags;
        int received = 0;
        int ret;

        /* process all communication messages */
        while (true) {
                struct ican3_msg msg;
                ret = ican3_recv_msg(mod, &msg);
                if (ret)
                        break;

                ican3_handle_message(mod, &msg);
        }

        /* process all CAN frames from the fast interface */
        while (received < budget) {
                ret = ican3_recv_skb(mod);
                if (ret)
                        break;

                received++;
        }

        /* We have processed all packets that the adapter had, but it
         * was less than our budget, stop polling */
        if (received < budget)
                napi_complete(napi);

        spin_lock_irqsave(&mod->lock, flags);

        /* Wake up the transmit queue if necessary */
        if (netif_queue_stopped(mod->ndev) && ican3_txok(mod))
                netif_wake_queue(mod->ndev);

        spin_unlock_irqrestore(&mod->lock, flags);

        /* re-enable interrupt generation */
        iowrite8(1 << mod->num, &mod->ctrl->int_enable);
        return received;
}

static irqreturn_t ican3_irq(int irq, void *dev_id)
{
        struct ican3_dev *mod = dev_id;
        u8 stat;

        /*
         * The interrupt status register on this device reports interrupts
         * as zeroes instead of using ones like most other devices
         */
        stat = ioread8(&mod->ctrl->int_disable) & (1 << mod->num);
        if (stat == (1 << mod->num))
                return IRQ_NONE;

        /* clear the MODULbus interrupt from the microcontroller */
        ioread8(&mod->dpmctrl->interrupt);

        /* disable interrupt generation, schedule the NAPI poller */
        iowrite8(1 << mod->num, &mod->ctrl->int_disable);
        napi_schedule(&mod->napi);
        return IRQ_HANDLED;
}

/*
 * Firmware reset, startup, and shutdown
 */

/*
 * Reset an ICAN module to its power-on state
 *
 * CONTEXT: no network device registered
 */
static int ican3_reset_module(struct ican3_dev *mod)
{
        unsigned long start;
        u8 runold, runnew;

        /* disable interrupts so no more work is scheduled */
        iowrite8(1 << mod->num, &mod->ctrl->int_disable);

        /* the first unallocated page in the DPM is #9 */
        mod->free_page = DPM_FREE_START;

        ican3_set_page(mod, QUEUE_OLD_CONTROL);
        runold = ioread8(mod->dpm + TARGET_RUNNING);

        /* reset the module */
        iowrite8(0x00, &mod->dpmctrl->hwreset);

        /* wait until the module has finished resetting and is running */
        start = jiffies;
        do {
                ican3_set_page(mod, QUEUE_OLD_CONTROL);
                runnew = ioread8(mod->dpm + TARGET_RUNNING);
                if (runnew == (runold ^ 0xff))
                        return 0;

                msleep(10);
        } while (time_before(jiffies, start + HZ / 4));

        dev_err(mod->dev, "failed to reset CAN module\n");
        return -ETIMEDOUT;
}

static void ican3_shutdown_module(struct ican3_dev *mod)
{
        ican3_msg_disconnect(mod);
        ican3_reset_module(mod);
}

/*
 * Startup an ICAN module, bringing it into fast mode
 */
static int ican3_startup_module(struct ican3_dev *mod)
{
        int ret;

        ret = ican3_reset_module(mod);
        if (ret) {
                dev_err(mod->dev, "unable to reset module\n");
                return ret;
        }

        /* re-enable interrupts so we can send messages */
        iowrite8(1 << mod->num, &mod->ctrl->int_enable);

        ret = ican3_msg_connect(mod);
        if (ret) {
                dev_err(mod->dev, "unable to connect to module\n");
                return ret;
        }

        ican3_init_new_host_interface(mod);
        ret = ican3_msg_newhostif(mod);
        if (ret) {
                dev_err(mod->dev, "unable to switch to new-style interface\n");
                return ret;
        }

        /* default to "termination on" */
        ret = ican3_set_termination(mod, true);
        if (ret) {
                dev_err(mod->dev, "unable to enable termination\n");
                return ret;
        }

        /* default to "bus errors enabled" */
        ret = ican3_set_buserror(mod, 1);
        if (ret) {
                dev_err(mod->dev, "unable to set bus-error\n");
                return ret;
        }

        ican3_init_fast_host_interface(mod);
        ret = ican3_msg_fasthostif(mod);
        if (ret) {
                dev_err(mod->dev, "unable to switch to fast host interface\n");
                return ret;
        }

        ret = ican3_set_id_filter(mod, true);
        if (ret) {
                dev_err(mod->dev, "unable to set acceptance filter\n");
                return ret;
        }

        return 0;
}

/*
 * CAN Network Device
 */

static int ican3_open(struct net_device *ndev)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        int ret;

        /* open the CAN layer */
        ret = open_candev(ndev);
        if (ret) {
                dev_err(mod->dev, "unable to start CAN layer\n");
                return ret;
        }

        /* bring the bus online */
        ret = ican3_set_bus_state(mod, true);
        if (ret) {
                dev_err(mod->dev, "unable to set bus-on\n");
                close_candev(ndev);
                return ret;
        }

        /* start up the network device */
        mod->can.state = CAN_STATE_ERROR_ACTIVE;
        netif_start_queue(ndev);

        return 0;
}

static int ican3_stop(struct net_device *ndev)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        int ret;

        /* stop the network device xmit routine */
        netif_stop_queue(ndev);
        mod->can.state = CAN_STATE_STOPPED;

        /* bring the bus offline, stop receiving packets */
        ret = ican3_set_bus_state(mod, false);
        if (ret) {
                dev_err(mod->dev, "unable to set bus-off\n");
                return ret;
        }

        /* drop all outstanding echo skbs */
        skb_queue_purge(&mod->echoq);

        /* close the CAN layer */
        close_candev(ndev);
        return 0;
}

static int ican3_xmit(struct sk_buff *skb, struct net_device *ndev)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        struct can_frame *cf = (struct can_frame *)skb->data;
        struct ican3_fast_desc desc;
        void __iomem *desc_addr;
        unsigned long flags;

        if (can_dropped_invalid_skb(ndev, skb))
                return NETDEV_TX_OK;

        spin_lock_irqsave(&mod->lock, flags);

        /* check that we can actually transmit */
        if (!ican3_txok(mod)) {
                dev_err(mod->dev, "BUG: no free descriptors\n");
                spin_unlock_irqrestore(&mod->lock, flags);
                return NETDEV_TX_BUSY;
        }

        /* copy the control bits of the descriptor */
        ican3_set_page(mod, mod->fasttx_start + (mod->fasttx_num / 16));
        desc_addr = mod->dpm + ((mod->fasttx_num % 16) * sizeof(desc));
        memset(&desc, 0, sizeof(desc));
        memcpy_fromio(&desc, desc_addr, 1);

        /* convert the Linux CAN frame into ICAN3 format */
        can_frame_to_ican3(mod, cf, &desc);

        /*
         * This hardware doesn't have TX-done notifications, so we'll try and
         * emulate it the best we can using ECHO skbs. Add the skb to the ECHO
         * stack. Upon packet reception, check if the ECHO skb and received
         * skb match, and use that to wake the queue.
         */
        ican3_put_echo_skb(mod, skb);

        /*
         * the programming manual says that you must set the IVALID bit, then
         * interrupt, then set the valid bit. Quite weird, but it seems to be
         * required for this to work
         */
        desc.control |= DESC_IVALID;
        memcpy_toio(desc_addr, &desc, sizeof(desc));

        /* generate a MODULbus interrupt to the microcontroller */
        iowrite8(0x01, &mod->dpmctrl->interrupt);

        desc.control ^= DESC_VALID;
        memcpy_toio(desc_addr, &desc, sizeof(desc));

        /* update the next buffer pointer */
        mod->fasttx_num = (desc.control & DESC_WRAP) ? 0
                                                     : (mod->fasttx_num + 1);

        /* if there is no free descriptor space, stop the transmit queue */
        if (!ican3_txok(mod))
                netif_stop_queue(ndev);

        spin_unlock_irqrestore(&mod->lock, flags);
        return NETDEV_TX_OK;
}

static const struct net_device_ops ican3_netdev_ops = {
        .ndo_open       = ican3_open,
        .ndo_stop       = ican3_stop,
        .ndo_start_xmit = ican3_xmit,
};

/*
 * Low-level CAN Device
 */

/* This structure was stolen from drivers/net/can/sja1000/sja1000.c */
static const struct can_bittiming_const ican3_bittiming_const = {
        .name = DRV_NAME,
        .tseg1_min = 1,
        .tseg1_max = 16,
        .tseg2_min = 1,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 64,
        .brp_inc = 1,
};

/*
 * This routine was stolen from drivers/net/can/sja1000/sja1000.c
 *
 * The bittiming register command for the ICAN3 just sets the bit timing
 * registers on the SJA1000 chip directly
 */
static int ican3_set_bittiming(struct net_device *ndev)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        struct can_bittiming *bt = &mod->can.bittiming;
        struct ican3_msg msg;
        u8 btr0, btr1;

        btr0 = ((bt->brp - 1) & 0x3f) | (((bt->sjw - 1) & 0x3) << 6);
        btr1 = ((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) |
                (((bt->phase_seg2 - 1) & 0x7) << 4);
        if (mod->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
                btr1 |= 0x80;

        memset(&msg, 0, sizeof(msg));
        msg.spec = MSG_CBTRREQ;
        msg.len = cpu_to_le16(4);
        msg.data[0] = 0x00;
        msg.data[1] = 0x00;
        msg.data[2] = btr0;
        msg.data[3] = btr1;

        return ican3_send_msg(mod, &msg);
}

static int ican3_set_mode(struct net_device *ndev, enum can_mode mode)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        int ret;

        if (mode != CAN_MODE_START)
                return -ENOTSUPP;

        /* bring the bus online */
        ret = ican3_set_bus_state(mod, true);
        if (ret) {
                dev_err(mod->dev, "unable to set bus-on\n");
                return ret;
        }

        /* start up the network device */
        mod->can.state = CAN_STATE_ERROR_ACTIVE;

        if (netif_queue_stopped(ndev))
                netif_wake_queue(ndev);

        return 0;
}

static int ican3_get_berr_counter(const struct net_device *ndev,
                                  struct can_berr_counter *bec)
{
        struct ican3_dev *mod = netdev_priv(ndev);
        int ret;

        ret = ican3_send_inquiry(mod, INQUIRY_STATUS);
        if (ret)
                return ret;

        ret = wait_for_completion_timeout(&mod->buserror_comp, HZ);
        if (ret == 0) {
                dev_info(mod->dev, "%s timed out\n", __func__);
                return -ETIMEDOUT;
        }

        bec->rxerr = mod->bec.rxerr;
        bec->txerr = mod->bec.txerr;
        return 0;
}

/*
 * Sysfs Attributes
 */

static ssize_t ican3_sysfs_show_term(struct device *dev,
                                     struct device_attribute *attr,
                                     char *buf)
{
        struct ican3_dev *mod = netdev_priv(to_net_dev(dev));
        int ret;

        ret = ican3_send_inquiry(mod, INQUIRY_TERMINATION);
        if (ret)
                return ret;

        ret = wait_for_completion_timeout(&mod->termination_comp, HZ);
        if (ret == 0) {
                dev_info(mod->dev, "%s timed out\n", __func__);
                return -ETIMEDOUT;
        }

        return snprintf(buf, PAGE_SIZE, "%u\n", mod->termination_enabled);
}

static ssize_t ican3_sysfs_set_term(struct device *dev,
                                    struct device_attribute *attr,
                                    const char *buf, size_t count)
{
        struct ican3_dev *mod = netdev_priv(to_net_dev(dev));
        unsigned long enable;
        int ret;

        if (kstrtoul(buf, 0, &enable))
                return -EINVAL;

        ret = ican3_set_termination(mod, enable);
        if (ret)
                return ret;

        return count;
}

static DEVICE_ATTR(termination, S_IWUSR | S_IRUGO, ican3_sysfs_show_term,
                                                   ican3_sysfs_set_term);

static struct attribute *ican3_sysfs_attrs[] = {
        &dev_attr_termination.attr,
        NULL,
};

static struct attribute_group ican3_sysfs_attr_group = {
        .attrs = ican3_sysfs_attrs,
};

/*
 * PCI Subsystem
 */

static int ican3_probe(struct platform_device *pdev)
{
        struct janz_platform_data *pdata;
        struct net_device *ndev;
        struct ican3_dev *mod;
        struct resource *res;
        struct device *dev;
        int ret;

        pdata = pdev->dev.platform_data;
        if (!pdata)
                return -ENXIO;

        dev_dbg(&pdev->dev, "probe: module number %d\n", pdata->modno);

        /* save the struct device for printing */
        dev = &pdev->dev;

        /* allocate the CAN device and private data */
        ndev = alloc_candev(sizeof(*mod), 0);
        if (!ndev) {
                dev_err(dev, "unable to allocate CANdev\n");
                ret = -ENOMEM;
                goto out_return;
        }

        platform_set_drvdata(pdev, ndev);
        mod = netdev_priv(ndev);
        mod->ndev = ndev;
        mod->dev = &pdev->dev;
        mod->num = pdata->modno;
        netif_napi_add(ndev, &mod->napi, ican3_napi, ICAN3_RX_BUFFERS);
        skb_queue_head_init(&mod->echoq);
        spin_lock_init(&mod->lock);
        init_completion(&mod->termination_comp);
        init_completion(&mod->buserror_comp);

        /* setup device-specific sysfs attributes */
        ndev->sysfs_groups[0] = &ican3_sysfs_attr_group;

        /* the first unallocated page in the DPM is 9 */
        mod->free_page = DPM_FREE_START;

        ndev->netdev_ops = &ican3_netdev_ops;
        ndev->flags |= IFF_ECHO;
        SET_NETDEV_DEV(ndev, &pdev->dev);

        mod->can.clock.freq = ICAN3_CAN_CLOCK;
        mod->can.bittiming_const = &ican3_bittiming_const;
        mod->can.do_set_bittiming = ican3_set_bittiming;
        mod->can.do_set_mode = ican3_set_mode;
        mod->can.do_get_berr_counter = ican3_get_berr_counter;
        mod->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES
                                    | CAN_CTRLMODE_BERR_REPORTING
                                    | CAN_CTRLMODE_ONE_SHOT;

        /* find our IRQ number */
        mod->irq = platform_get_irq(pdev, 0);
        if (mod->irq < 0) {
                dev_err(dev, "IRQ line not found\n");
                ret = -ENODEV;
                goto out_free_ndev;
        }

        ndev->irq = mod->irq;

        /* get access to the MODULbus registers for this module */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(dev, "MODULbus registers not found\n");
                ret = -ENODEV;
                goto out_free_ndev;
        }

        mod->dpm = ioremap(res->start, resource_size(res));
        if (!mod->dpm) {
                dev_err(dev, "MODULbus registers not ioremap\n");
                ret = -ENOMEM;
                goto out_free_ndev;
        }

        mod->dpmctrl = mod->dpm + DPM_PAGE_SIZE;

        /* get access to the control registers for this module */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
        if (!res) {
                dev_err(dev, "CONTROL registers not found\n");
                ret = -ENODEV;
                goto out_iounmap_dpm;
        }

        mod->ctrl = ioremap(res->start, resource_size(res));
        if (!mod->ctrl) {
                dev_err(dev, "CONTROL registers not ioremap\n");
                ret = -ENOMEM;
                goto out_iounmap_dpm;
        }

        /* disable our IRQ, then hookup the IRQ handler */
        iowrite8(1 << mod->num, &mod->ctrl->int_disable);
        ret = request_irq(mod->irq, ican3_irq, IRQF_SHARED, DRV_NAME, mod);
        if (ret) {
                dev_err(dev, "unable to request IRQ\n");
                goto out_iounmap_ctrl;
        }

        /* reset and initialize the CAN controller into fast mode */
        napi_enable(&mod->napi);
        ret = ican3_startup_module(mod);
        if (ret) {
                dev_err(dev, "%s: unable to start CANdev\n", __func__);
                goto out_free_irq;
        }

        /* register with the Linux CAN layer */
        ret = register_candev(ndev);
        if (ret) {
                dev_err(dev, "%s: unable to register CANdev\n", __func__);
                goto out_free_irq;
        }

        dev_info(dev, "module %d: registered CAN device\n", pdata->modno);
        return 0;

out_free_irq:
        napi_disable(&mod->napi);
        iowrite8(1 << mod->num, &mod->ctrl->int_disable);
        free_irq(mod->irq, mod);
out_iounmap_ctrl:
        iounmap(mod->ctrl);
out_iounmap_dpm:
        iounmap(mod->dpm);
out_free_ndev:
        free_candev(ndev);
out_return:
        return ret;
}

static int ican3_remove(struct platform_device *pdev)
{
        struct net_device *ndev = platform_get_drvdata(pdev);
        struct ican3_dev *mod = netdev_priv(ndev);

        /* unregister the netdevice, stop interrupts */
        unregister_netdev(ndev);
        napi_disable(&mod->napi);
        iowrite8(1 << mod->num, &mod->ctrl->int_disable);
        free_irq(mod->irq, mod);

        /* put the module into reset */
        ican3_shutdown_module(mod);

        /* unmap all registers */
        iounmap(mod->ctrl);
        iounmap(mod->dpm);

        free_candev(ndev);

        return 0;
}

static struct platform_driver ican3_driver = {
        .driver         = {
                .name   = DRV_NAME,
                .owner  = THIS_MODULE,
        },
        .probe          = ican3_probe,
        .remove         = ican3_remove,
};

module_platform_driver(ican3_driver);

MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
MODULE_DESCRIPTION("Janz MODULbus VMOD-ICAN3 Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:janz-ican3");