Linux 4.2.1

[linux/fpc-iii.git] / drivers / spi / spi-ep93xx.c

/*
 * Driver for Cirrus Logic EP93xx SPI controller.
 *
 * Copyright (C) 2010-2011 Mika Westerberg
 *
 * Explicit FIFO handling code was inspired by amba-pl022 driver.
 *
 * Chip select support using other than built-in GPIOs by H. Hartley Sweeten.
 *
 * For more information about the SPI controller see documentation on Cirrus
 * Logic web site:
 *     http://www.cirrus.com/en/pubs/manual/EP93xx_Users_Guide_UM1.pdf
 *
 * 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.
 */

#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dmaengine.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/scatterlist.h>
#include <linux/spi/spi.h>

#include <linux/platform_data/dma-ep93xx.h>
#include <linux/platform_data/spi-ep93xx.h>

#define SSPCR0                  0x0000
#define SSPCR0_MODE_SHIFT       6
#define SSPCR0_SCR_SHIFT        8

#define SSPCR1                  0x0004
#define SSPCR1_RIE              BIT(0)
#define SSPCR1_TIE              BIT(1)
#define SSPCR1_RORIE            BIT(2)
#define SSPCR1_LBM              BIT(3)
#define SSPCR1_SSE              BIT(4)
#define SSPCR1_MS               BIT(5)
#define SSPCR1_SOD              BIT(6)

#define SSPDR                   0x0008

#define SSPSR                   0x000c
#define SSPSR_TFE               BIT(0)
#define SSPSR_TNF               BIT(1)
#define SSPSR_RNE               BIT(2)
#define SSPSR_RFF               BIT(3)
#define SSPSR_BSY               BIT(4)
#define SSPCPSR                 0x0010

#define SSPIIR                  0x0014
#define SSPIIR_RIS              BIT(0)
#define SSPIIR_TIS              BIT(1)
#define SSPIIR_RORIS            BIT(2)
#define SSPICR                  SSPIIR

/* timeout in milliseconds */
#define SPI_TIMEOUT             5
/* maximum depth of RX/TX FIFO */
#define SPI_FIFO_SIZE           8

/**
 * struct ep93xx_spi - EP93xx SPI controller structure
 * @pdev: pointer to platform device
 * @clk: clock for the controller
 * @regs_base: pointer to ioremap()'d registers
 * @sspdr_phys: physical address of the SSPDR register
 * @wait: wait here until given transfer is completed
 * @current_msg: message that is currently processed (or %NULL if none)
 * @tx: current byte in transfer to transmit
 * @rx: current byte in transfer to receive
 * @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
 *              frame decreases this level and sending one frame increases it.
 * @dma_rx: RX DMA channel
 * @dma_tx: TX DMA channel
 * @dma_rx_data: RX parameters passed to the DMA engine
 * @dma_tx_data: TX parameters passed to the DMA engine
 * @rx_sgt: sg table for RX transfers
 * @tx_sgt: sg table for TX transfers
 * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by
 *            the client
 */
struct ep93xx_spi {
        const struct platform_device    *pdev;
        struct clk                      *clk;
        void __iomem                    *regs_base;
        unsigned long                   sspdr_phys;
        struct completion               wait;
        struct spi_message              *current_msg;
        size_t                          tx;
        size_t                          rx;
        size_t                          fifo_level;
        struct dma_chan                 *dma_rx;
        struct dma_chan                 *dma_tx;
        struct ep93xx_dma_data          dma_rx_data;
        struct ep93xx_dma_data          dma_tx_data;
        struct sg_table                 rx_sgt;
        struct sg_table                 tx_sgt;
        void                            *zeropage;
};

/**
 * struct ep93xx_spi_chip - SPI device hardware settings
 * @spi: back pointer to the SPI device
 * @ops: private chip operations
 */
struct ep93xx_spi_chip {
        const struct spi_device         *spi;
        struct ep93xx_spi_chip_ops      *ops;
};

/* converts bits per word to CR0.DSS value */
#define bits_per_word_to_dss(bpw)       ((bpw) - 1)

static void ep93xx_spi_write_u8(const struct ep93xx_spi *espi,
                                u16 reg, u8 value)
{
        writeb(value, espi->regs_base + reg);
}

static u8 ep93xx_spi_read_u8(const struct ep93xx_spi *spi, u16 reg)
{
        return readb(spi->regs_base + reg);
}

static void ep93xx_spi_write_u16(const struct ep93xx_spi *espi,
                                 u16 reg, u16 value)
{
        writew(value, espi->regs_base + reg);
}

static u16 ep93xx_spi_read_u16(const struct ep93xx_spi *spi, u16 reg)
{
        return readw(spi->regs_base + reg);
}

static int ep93xx_spi_enable(const struct ep93xx_spi *espi)
{
        u8 regval;
        int err;

        err = clk_enable(espi->clk);
        if (err)
                return err;

        regval = ep93xx_spi_read_u8(espi, SSPCR1);
        regval |= SSPCR1_SSE;
        ep93xx_spi_write_u8(espi, SSPCR1, regval);

        return 0;
}

static void ep93xx_spi_disable(const struct ep93xx_spi *espi)
{
        u8 regval;

        regval = ep93xx_spi_read_u8(espi, SSPCR1);
        regval &= ~SSPCR1_SSE;
        ep93xx_spi_write_u8(espi, SSPCR1, regval);

        clk_disable(espi->clk);
}

static void ep93xx_spi_enable_interrupts(const struct ep93xx_spi *espi)
{
        u8 regval;

        regval = ep93xx_spi_read_u8(espi, SSPCR1);
        regval |= (SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
        ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

static void ep93xx_spi_disable_interrupts(const struct ep93xx_spi *espi)
{
        u8 regval;

        regval = ep93xx_spi_read_u8(espi, SSPCR1);
        regval &= ~(SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
        ep93xx_spi_write_u8(espi, SSPCR1, regval);
}

/**
 * ep93xx_spi_calc_divisors() - calculates SPI clock divisors
 * @espi: ep93xx SPI controller struct
 * @rate: desired SPI output clock rate
 * @div_cpsr: pointer to return the cpsr (pre-scaler) divider
 * @div_scr: pointer to return the scr divider
 */
static int ep93xx_spi_calc_divisors(const struct ep93xx_spi *espi,
                                    u32 rate, u8 *div_cpsr, u8 *div_scr)
{
        struct spi_master *master = platform_get_drvdata(espi->pdev);
        unsigned long spi_clk_rate = clk_get_rate(espi->clk);
        int cpsr, scr;

        /*
         * Make sure that max value is between values supported by the
         * controller. Note that minimum value is already checked in
         * ep93xx_spi_transfer_one_message().
         */
        rate = clamp(rate, master->min_speed_hz, master->max_speed_hz);

        /*
         * Calculate divisors so that we can get speed according the
         * following formula:
         *      rate = spi_clock_rate / (cpsr * (1 + scr))
         *
         * cpsr must be even number and starts from 2, scr can be any number
         * between 0 and 255.
         */
        for (cpsr = 2; cpsr <= 254; cpsr += 2) {
                for (scr = 0; scr <= 255; scr++) {
                        if ((spi_clk_rate / (cpsr * (scr + 1))) <= rate) {
                                *div_scr = (u8)scr;
                                *div_cpsr = (u8)cpsr;
                                return 0;
                        }
                }
        }

        return -EINVAL;
}

static void ep93xx_spi_cs_control(struct spi_device *spi, bool control)
{
        struct ep93xx_spi_chip *chip = spi_get_ctldata(spi);
        int value = (spi->mode & SPI_CS_HIGH) ? control : !control;

        if (chip->ops && chip->ops->cs_control)
                chip->ops->cs_control(spi, value);
}

/**
 * ep93xx_spi_setup() - setup an SPI device
 * @spi: SPI device to setup
 *
 * This function sets up SPI device mode, speed etc. Can be called multiple
 * times for a single device. Returns %0 in case of success, negative error in
 * case of failure. When this function returns success, the device is
 * deselected.
 */
static int ep93xx_spi_setup(struct spi_device *spi)
{
        struct ep93xx_spi *espi = spi_master_get_devdata(spi->master);
        struct ep93xx_spi_chip *chip;

        chip = spi_get_ctldata(spi);
        if (!chip) {
                dev_dbg(&espi->pdev->dev, "initial setup for %s\n",
                        spi->modalias);

                chip = kzalloc(sizeof(*chip), GFP_KERNEL);
                if (!chip)
                        return -ENOMEM;

                chip->spi = spi;
                chip->ops = spi->controller_data;

                if (chip->ops && chip->ops->setup) {
                        int ret = chip->ops->setup(spi);

                        if (ret) {
                                kfree(chip);
                                return ret;
                        }
                }

                spi_set_ctldata(spi, chip);
        }

        ep93xx_spi_cs_control(spi, false);
        return 0;
}

/**
 * ep93xx_spi_cleanup() - cleans up master controller specific state
 * @spi: SPI device to cleanup
 *
 * This function releases master controller specific state for given @spi
 * device.
 */
static void ep93xx_spi_cleanup(struct spi_device *spi)
{
        struct ep93xx_spi_chip *chip;

        chip = spi_get_ctldata(spi);
        if (chip) {
                if (chip->ops && chip->ops->cleanup)
                        chip->ops->cleanup(spi);
                spi_set_ctldata(spi, NULL);
                kfree(chip);
        }
}

/**
 * ep93xx_spi_chip_setup() - configures hardware according to given @chip
 * @espi: ep93xx SPI controller struct
 * @chip: chip specific settings
 * @speed_hz: transfer speed
 * @bits_per_word: transfer bits_per_word
 */
static int ep93xx_spi_chip_setup(const struct ep93xx_spi *espi,
                                 const struct ep93xx_spi_chip *chip,
                                 u32 speed_hz, u8 bits_per_word)
{
        u8 dss = bits_per_word_to_dss(bits_per_word);
        u8 div_cpsr = 0;
        u8 div_scr = 0;
        u16 cr0;
        int err;

        err = ep93xx_spi_calc_divisors(espi, speed_hz, &div_cpsr, &div_scr);
        if (err)
                return err;

        cr0 = div_scr << SSPCR0_SCR_SHIFT;
        cr0 |= (chip->spi->mode & (SPI_CPHA|SPI_CPOL)) << SSPCR0_MODE_SHIFT;
        cr0 |= dss;

        dev_dbg(&espi->pdev->dev, "setup: mode %d, cpsr %d, scr %d, dss %d\n",
                chip->spi->mode, div_cpsr, div_scr, dss);
        dev_dbg(&espi->pdev->dev, "setup: cr0 %#x\n", cr0);

        ep93xx_spi_write_u8(espi, SSPCPSR, div_cpsr);
        ep93xx_spi_write_u16(espi, SSPCR0, cr0);

        return 0;
}

static void ep93xx_do_write(struct ep93xx_spi *espi, struct spi_transfer *t)
{
        if (t->bits_per_word > 8) {
                u16 tx_val = 0;

                if (t->tx_buf)
                        tx_val = ((u16 *)t->tx_buf)[espi->tx];
                ep93xx_spi_write_u16(espi, SSPDR, tx_val);
                espi->tx += sizeof(tx_val);
        } else {
                u8 tx_val = 0;

                if (t->tx_buf)
                        tx_val = ((u8 *)t->tx_buf)[espi->tx];
                ep93xx_spi_write_u8(espi, SSPDR, tx_val);
                espi->tx += sizeof(tx_val);
        }
}

static void ep93xx_do_read(struct ep93xx_spi *espi, struct spi_transfer *t)
{
        if (t->bits_per_word > 8) {
                u16 rx_val;

                rx_val = ep93xx_spi_read_u16(espi, SSPDR);
                if (t->rx_buf)
                        ((u16 *)t->rx_buf)[espi->rx] = rx_val;
                espi->rx += sizeof(rx_val);
        } else {
                u8 rx_val;

                rx_val = ep93xx_spi_read_u8(espi, SSPDR);
                if (t->rx_buf)
                        ((u8 *)t->rx_buf)[espi->rx] = rx_val;
                espi->rx += sizeof(rx_val);
        }
}

/**
 * ep93xx_spi_read_write() - perform next RX/TX transfer
 * @espi: ep93xx SPI controller struct
 *
 * This function transfers next bytes (or half-words) to/from RX/TX FIFOs. If
 * called several times, the whole transfer will be completed. Returns
 * %-EINPROGRESS when current transfer was not yet completed otherwise %0.
 *
 * When this function is finished, RX FIFO should be empty and TX FIFO should be
 * full.
 */
static int ep93xx_spi_read_write(struct ep93xx_spi *espi)
{
        struct spi_message *msg = espi->current_msg;
        struct spi_transfer *t = msg->state;

        /* read as long as RX FIFO has frames in it */
        while ((ep93xx_spi_read_u8(espi, SSPSR) & SSPSR_RNE)) {
                ep93xx_do_read(espi, t);
                espi->fifo_level--;
        }

        /* write as long as TX FIFO has room */
        while (espi->fifo_level < SPI_FIFO_SIZE && espi->tx < t->len) {
                ep93xx_do_write(espi, t);
                espi->fifo_level++;
        }

        if (espi->rx == t->len)
                return 0;

        return -EINPROGRESS;
}

static void ep93xx_spi_pio_transfer(struct ep93xx_spi *espi)
{
        /*
         * Now everything is set up for the current transfer. We prime the TX
         * FIFO, enable interrupts, and wait for the transfer to complete.
         */
        if (ep93xx_spi_read_write(espi)) {
                ep93xx_spi_enable_interrupts(espi);
                wait_for_completion(&espi->wait);
        }
}

/**
 * ep93xx_spi_dma_prepare() - prepares a DMA transfer
 * @espi: ep93xx SPI controller struct
 * @dir: DMA transfer direction
 *
 * Function configures the DMA, maps the buffer and prepares the DMA
 * descriptor. Returns a valid DMA descriptor in case of success and ERR_PTR
 * in case of failure.
 */
static struct dma_async_tx_descriptor *
ep93xx_spi_dma_prepare(struct ep93xx_spi *espi, enum dma_transfer_direction dir)
{
        struct spi_transfer *t = espi->current_msg->state;
        struct dma_async_tx_descriptor *txd;
        enum dma_slave_buswidth buswidth;
        struct dma_slave_config conf;
        struct scatterlist *sg;
        struct sg_table *sgt;
        struct dma_chan *chan;
        const void *buf, *pbuf;
        size_t len = t->len;
        int i, ret, nents;

        if (t->bits_per_word > 8)
                buswidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
        else
                buswidth = DMA_SLAVE_BUSWIDTH_1_BYTE;

        memset(&conf, 0, sizeof(conf));
        conf.direction = dir;

        if (dir == DMA_DEV_TO_MEM) {
                chan = espi->dma_rx;
                buf = t->rx_buf;
                sgt = &espi->rx_sgt;

                conf.src_addr = espi->sspdr_phys;
                conf.src_addr_width = buswidth;
        } else {
                chan = espi->dma_tx;
                buf = t->tx_buf;
                sgt = &espi->tx_sgt;

                conf.dst_addr = espi->sspdr_phys;
                conf.dst_addr_width = buswidth;
        }

        ret = dmaengine_slave_config(chan, &conf);
        if (ret)
                return ERR_PTR(ret);

        /*
         * We need to split the transfer into PAGE_SIZE'd chunks. This is
         * because we are using @espi->zeropage to provide a zero RX buffer
         * for the TX transfers and we have only allocated one page for that.
         *
         * For performance reasons we allocate a new sg_table only when
         * needed. Otherwise we will re-use the current one. Eventually the
         * last sg_table is released in ep93xx_spi_release_dma().
         */

        nents = DIV_ROUND_UP(len, PAGE_SIZE);
        if (nents != sgt->nents) {
                sg_free_table(sgt);

                ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
                if (ret)
                        return ERR_PTR(ret);
        }

        pbuf = buf;
        for_each_sg(sgt->sgl, sg, sgt->nents, i) {
                size_t bytes = min_t(size_t, len, PAGE_SIZE);

                if (buf) {
                        sg_set_page(sg, virt_to_page(pbuf), bytes,
                                    offset_in_page(pbuf));
                } else {
                        sg_set_page(sg, virt_to_page(espi->zeropage),
                                    bytes, 0);
                }

                pbuf += bytes;
                len -= bytes;
        }

        if (WARN_ON(len)) {
                dev_warn(&espi->pdev->dev, "len = %zu expected 0!\n", len);
                return ERR_PTR(-EINVAL);
        }

        nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
        if (!nents)
                return ERR_PTR(-ENOMEM);

        txd = dmaengine_prep_slave_sg(chan, sgt->sgl, nents, dir, DMA_CTRL_ACK);
        if (!txd) {
                dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
                return ERR_PTR(-ENOMEM);
        }
        return txd;
}

/**
 * ep93xx_spi_dma_finish() - finishes with a DMA transfer
 * @espi: ep93xx SPI controller struct
 * @dir: DMA transfer direction
 *
 * Function finishes with the DMA transfer. After this, the DMA buffer is
 * unmapped.
 */
static void ep93xx_spi_dma_finish(struct ep93xx_spi *espi,
                                  enum dma_transfer_direction dir)
{
        struct dma_chan *chan;
        struct sg_table *sgt;

        if (dir == DMA_DEV_TO_MEM) {
                chan = espi->dma_rx;
                sgt = &espi->rx_sgt;
        } else {
                chan = espi->dma_tx;
                sgt = &espi->tx_sgt;
        }

        dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
}

static void ep93xx_spi_dma_callback(void *callback_param)
{
        complete(callback_param);
}

static void ep93xx_spi_dma_transfer(struct ep93xx_spi *espi)
{
        struct spi_message *msg = espi->current_msg;
        struct dma_async_tx_descriptor *rxd, *txd;

        rxd = ep93xx_spi_dma_prepare(espi, DMA_DEV_TO_MEM);
        if (IS_ERR(rxd)) {
                dev_err(&espi->pdev->dev, "DMA RX failed: %ld\n", PTR_ERR(rxd));
                msg->status = PTR_ERR(rxd);
                return;
        }

        txd = ep93xx_spi_dma_prepare(espi, DMA_MEM_TO_DEV);
        if (IS_ERR(txd)) {
                ep93xx_spi_dma_finish(espi, DMA_DEV_TO_MEM);
                dev_err(&espi->pdev->dev, "DMA TX failed: %ld\n", PTR_ERR(rxd));
                msg->status = PTR_ERR(txd);
                return;
        }

        /* We are ready when RX is done */
        rxd->callback = ep93xx_spi_dma_callback;
        rxd->callback_param = &espi->wait;

        /* Now submit both descriptors and wait while they finish */
        dmaengine_submit(rxd);
        dmaengine_submit(txd);

        dma_async_issue_pending(espi->dma_rx);
        dma_async_issue_pending(espi->dma_tx);

        wait_for_completion(&espi->wait);

        ep93xx_spi_dma_finish(espi, DMA_MEM_TO_DEV);
        ep93xx_spi_dma_finish(espi, DMA_DEV_TO_MEM);
}

/**
 * ep93xx_spi_process_transfer() - processes one SPI transfer
 * @espi: ep93xx SPI controller struct
 * @msg: current message
 * @t: transfer to process
 *
 * This function processes one SPI transfer given in @t. Function waits until
 * transfer is complete (may sleep) and updates @msg->status based on whether
 * transfer was successfully processed or not.
 */
static void ep93xx_spi_process_transfer(struct ep93xx_spi *espi,
                                        struct spi_message *msg,
                                        struct spi_transfer *t)
{
        struct ep93xx_spi_chip *chip = spi_get_ctldata(msg->spi);
        int err;

        msg->state = t;

        err = ep93xx_spi_chip_setup(espi, chip, t->speed_hz, t->bits_per_word);
        if (err) {
                dev_err(&espi->pdev->dev,
                        "failed to setup chip for transfer\n");
                msg->status = err;
                return;
        }

        espi->rx = 0;
        espi->tx = 0;

        /*
         * There is no point of setting up DMA for the transfers which will
         * fit into the FIFO and can be transferred with a single interrupt.
         * So in these cases we will be using PIO and don't bother for DMA.
         */
        if (espi->dma_rx && t->len > SPI_FIFO_SIZE)
                ep93xx_spi_dma_transfer(espi);
        else
                ep93xx_spi_pio_transfer(espi);

        /*
         * In case of error during transmit, we bail out from processing
         * the message.
         */
        if (msg->status)
                return;

        msg->actual_length += t->len;

        /*
         * After this transfer is finished, perform any possible
         * post-transfer actions requested by the protocol driver.
         */
        if (t->delay_usecs) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(usecs_to_jiffies(t->delay_usecs));
        }
        if (t->cs_change) {
                if (!list_is_last(&t->transfer_list, &msg->transfers)) {
                        /*
                         * In case protocol driver is asking us to drop the
                         * chipselect briefly, we let the scheduler to handle
                         * any "delay" here.
                         */
                        ep93xx_spi_cs_control(msg->spi, false);
                        cond_resched();
                        ep93xx_spi_cs_control(msg->spi, true);
                }
        }
}

/*
 * ep93xx_spi_process_message() - process one SPI message
 * @espi: ep93xx SPI controller struct
 * @msg: message to process
 *
 * This function processes a single SPI message. We go through all transfers in
 * the message and pass them to ep93xx_spi_process_transfer(). Chipselect is
 * asserted during the whole message (unless per transfer cs_change is set).
 *
 * @msg->status contains %0 in case of success or negative error code in case of
 * failure.
 */
static void ep93xx_spi_process_message(struct ep93xx_spi *espi,
                                       struct spi_message *msg)
{
        unsigned long timeout;
        struct spi_transfer *t;
        int err;

        /*
         * Enable the SPI controller and its clock.
         */
        err = ep93xx_spi_enable(espi);
        if (err) {
                dev_err(&espi->pdev->dev, "failed to enable SPI controller\n");
                msg->status = err;
                return;
        }

        /*
         * Just to be sure: flush any data from RX FIFO.
         */
        timeout = jiffies + msecs_to_jiffies(SPI_TIMEOUT);
        while (ep93xx_spi_read_u16(espi, SSPSR) & SSPSR_RNE) {
                if (time_after(jiffies, timeout)) {
                        dev_warn(&espi->pdev->dev,
                                 "timeout while flushing RX FIFO\n");
                        msg->status = -ETIMEDOUT;
                        return;
                }
                ep93xx_spi_read_u16(espi, SSPDR);
        }

        /*
         * We explicitly handle FIFO level. This way we don't have to check TX
         * FIFO status using %SSPSR_TNF bit which may cause RX FIFO overruns.
         */
        espi->fifo_level = 0;

        /*
         * Assert the chipselect.
         */
        ep93xx_spi_cs_control(msg->spi, true);

        list_for_each_entry(t, &msg->transfers, transfer_list) {
                ep93xx_spi_process_transfer(espi, msg, t);
                if (msg->status)
                        break;
        }

        /*
         * Now the whole message is transferred (or failed for some reason). We
         * deselect the device and disable the SPI controller.
         */
        ep93xx_spi_cs_control(msg->spi, false);
        ep93xx_spi_disable(espi);
}

static int ep93xx_spi_transfer_one_message(struct spi_master *master,
                                           struct spi_message *msg)
{
        struct ep93xx_spi *espi = spi_master_get_devdata(master);

        msg->state = NULL;
        msg->status = 0;
        msg->actual_length = 0;

        espi->current_msg = msg;
        ep93xx_spi_process_message(espi, msg);
        espi->current_msg = NULL;

        spi_finalize_current_message(master);

        return 0;
}

static irqreturn_t ep93xx_spi_interrupt(int irq, void *dev_id)
{
        struct ep93xx_spi *espi = dev_id;
        u8 irq_status = ep93xx_spi_read_u8(espi, SSPIIR);

        /*
         * If we got ROR (receive overrun) interrupt we know that something is
         * wrong. Just abort the message.
         */
        if (unlikely(irq_status & SSPIIR_RORIS)) {
                /* clear the overrun interrupt */
                ep93xx_spi_write_u8(espi, SSPICR, 0);
                dev_warn(&espi->pdev->dev,
                         "receive overrun, aborting the message\n");
                espi->current_msg->status = -EIO;
        } else {
                /*
                 * Interrupt is either RX (RIS) or TX (TIS). For both cases we
                 * simply execute next data transfer.
                 */
                if (ep93xx_spi_read_write(espi)) {
                        /*
                         * In normal case, there still is some processing left
                         * for current transfer. Let's wait for the next
                         * interrupt then.
                         */
                        return IRQ_HANDLED;
                }
        }

        /*
         * Current transfer is finished, either with error or with success. In
         * any case we disable interrupts and notify the worker to handle
         * any post-processing of the message.
         */
        ep93xx_spi_disable_interrupts(espi);
        complete(&espi->wait);
        return IRQ_HANDLED;
}

static bool ep93xx_spi_dma_filter(struct dma_chan *chan, void *filter_param)
{
        if (ep93xx_dma_chan_is_m2p(chan))
                return false;

        chan->private = filter_param;
        return true;
}

static int ep93xx_spi_setup_dma(struct ep93xx_spi *espi)
{
        dma_cap_mask_t mask;
        int ret;

        espi->zeropage = (void *)get_zeroed_page(GFP_KERNEL);
        if (!espi->zeropage)
                return -ENOMEM;

        dma_cap_zero(mask);
        dma_cap_set(DMA_SLAVE, mask);

        espi->dma_rx_data.port = EP93XX_DMA_SSP;
        espi->dma_rx_data.direction = DMA_DEV_TO_MEM;
        espi->dma_rx_data.name = "ep93xx-spi-rx";

        espi->dma_rx = dma_request_channel(mask, ep93xx_spi_dma_filter,
                                           &espi->dma_rx_data);
        if (!espi->dma_rx) {
                ret = -ENODEV;
                goto fail_free_page;
        }

        espi->dma_tx_data.port = EP93XX_DMA_SSP;
        espi->dma_tx_data.direction = DMA_MEM_TO_DEV;
        espi->dma_tx_data.name = "ep93xx-spi-tx";

        espi->dma_tx = dma_request_channel(mask, ep93xx_spi_dma_filter,
                                           &espi->dma_tx_data);
        if (!espi->dma_tx) {
                ret = -ENODEV;
                goto fail_release_rx;
        }

        return 0;

fail_release_rx:
        dma_release_channel(espi->dma_rx);
        espi->dma_rx = NULL;
fail_free_page:
        free_page((unsigned long)espi->zeropage);

        return ret;
}

static void ep93xx_spi_release_dma(struct ep93xx_spi *espi)
{
        if (espi->dma_rx) {
                dma_release_channel(espi->dma_rx);
                sg_free_table(&espi->rx_sgt);
        }
        if (espi->dma_tx) {
                dma_release_channel(espi->dma_tx);
                sg_free_table(&espi->tx_sgt);
        }

        if (espi->zeropage)
                free_page((unsigned long)espi->zeropage);
}

static int ep93xx_spi_probe(struct platform_device *pdev)
{
        struct spi_master *master;
        struct ep93xx_spi_info *info;
        struct ep93xx_spi *espi;
        struct resource *res;
        int irq;
        int error;

        info = dev_get_platdata(&pdev->dev);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(&pdev->dev, "failed to get irq resources\n");
                return -EBUSY;
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(&pdev->dev, "unable to get iomem resource\n");
                return -ENODEV;
        }

        master = spi_alloc_master(&pdev->dev, sizeof(*espi));
        if (!master)
                return -ENOMEM;

        master->setup = ep93xx_spi_setup;
        master->transfer_one_message = ep93xx_spi_transfer_one_message;
        master->cleanup = ep93xx_spi_cleanup;
        master->bus_num = pdev->id;
        master->num_chipselect = info->num_chipselect;
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
        master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);

        platform_set_drvdata(pdev, master);

        espi = spi_master_get_devdata(master);

        espi->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(espi->clk)) {
                dev_err(&pdev->dev, "unable to get spi clock\n");
                error = PTR_ERR(espi->clk);
                goto fail_release_master;
        }

        init_completion(&espi->wait);

        /*
         * Calculate maximum and minimum supported clock rates
         * for the controller.
         */
        master->max_speed_hz = clk_get_rate(espi->clk) / 2;
        master->min_speed_hz = clk_get_rate(espi->clk) / (254 * 256);
        espi->pdev = pdev;

        espi->sspdr_phys = res->start + SSPDR;

        espi->regs_base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(espi->regs_base)) {
                error = PTR_ERR(espi->regs_base);
                goto fail_release_master;
        }

        error = devm_request_irq(&pdev->dev, irq, ep93xx_spi_interrupt,
                                0, "ep93xx-spi", espi);
        if (error) {
                dev_err(&pdev->dev, "failed to request irq\n");
                goto fail_release_master;
        }

        if (info->use_dma && ep93xx_spi_setup_dma(espi))
                dev_warn(&pdev->dev, "DMA setup failed. Falling back to PIO\n");

        /* make sure that the hardware is disabled */
        ep93xx_spi_write_u8(espi, SSPCR1, 0);

        error = devm_spi_register_master(&pdev->dev, master);
        if (error) {
                dev_err(&pdev->dev, "failed to register SPI master\n");
                goto fail_free_dma;
        }

        dev_info(&pdev->dev, "EP93xx SPI Controller at 0x%08lx irq %d\n",
                 (unsigned long)res->start, irq);

        return 0;

fail_free_dma:
        ep93xx_spi_release_dma(espi);
fail_release_master:
        spi_master_put(master);

        return error;
}

static int ep93xx_spi_remove(struct platform_device *pdev)
{
        struct spi_master *master = platform_get_drvdata(pdev);
        struct ep93xx_spi *espi = spi_master_get_devdata(master);

        ep93xx_spi_release_dma(espi);

        return 0;
}

static struct platform_driver ep93xx_spi_driver = {
        .driver         = {
                .name   = "ep93xx-spi",
        },
        .probe          = ep93xx_spi_probe,
        .remove         = ep93xx_spi_remove,
};
module_platform_driver(ep93xx_spi_driver);

MODULE_DESCRIPTION("EP93xx SPI Controller driver");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@iki.fi>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ep93xx-spi");