Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input

[linux-btrfs-devel.git] / drivers / spi / spi-davinci.c

/*
 * Copyright (C) 2009 Texas Instruments.
 * Copyright (C) 2010 EF Johnson Technologies
 *
 * 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.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/dma-mapping.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/slab.h>

#include <mach/spi.h>
#include <mach/edma.h>

#define SPI_NO_RESOURCE         ((resource_size_t)-1)

#define SPI_MAX_CHIPSELECT      2

#define CS_DEFAULT      0xFF

#define SPIFMT_PHASE_MASK       BIT(16)
#define SPIFMT_POLARITY_MASK    BIT(17)
#define SPIFMT_DISTIMER_MASK    BIT(18)
#define SPIFMT_SHIFTDIR_MASK    BIT(20)
#define SPIFMT_WAITENA_MASK     BIT(21)
#define SPIFMT_PARITYENA_MASK   BIT(22)
#define SPIFMT_ODD_PARITY_MASK  BIT(23)
#define SPIFMT_WDELAY_MASK      0x3f000000u
#define SPIFMT_WDELAY_SHIFT     24
#define SPIFMT_PRESCALE_SHIFT   8

/* SPIPC0 */
#define SPIPC0_DIFUN_MASK       BIT(11)         /* MISO */
#define SPIPC0_DOFUN_MASK       BIT(10)         /* MOSI */
#define SPIPC0_CLKFUN_MASK      BIT(9)          /* CLK */
#define SPIPC0_SPIENA_MASK      BIT(8)          /* nREADY */

#define SPIINT_MASKALL          0x0101035F
#define SPIINT_MASKINT          0x0000015F
#define SPI_INTLVL_1            0x000001FF
#define SPI_INTLVL_0            0x00000000

/* SPIDAT1 (upper 16 bit defines) */
#define SPIDAT1_CSHOLD_MASK     BIT(12)

/* SPIGCR1 */
#define SPIGCR1_CLKMOD_MASK     BIT(1)
#define SPIGCR1_MASTER_MASK     BIT(0)
#define SPIGCR1_POWERDOWN_MASK  BIT(8)
#define SPIGCR1_LOOPBACK_MASK   BIT(16)
#define SPIGCR1_SPIENA_MASK     BIT(24)

/* SPIBUF */
#define SPIBUF_TXFULL_MASK      BIT(29)
#define SPIBUF_RXEMPTY_MASK     BIT(31)

/* SPIDELAY */
#define SPIDELAY_C2TDELAY_SHIFT 24
#define SPIDELAY_C2TDELAY_MASK  (0xFF << SPIDELAY_C2TDELAY_SHIFT)
#define SPIDELAY_T2CDELAY_SHIFT 16
#define SPIDELAY_T2CDELAY_MASK  (0xFF << SPIDELAY_T2CDELAY_SHIFT)
#define SPIDELAY_T2EDELAY_SHIFT 8
#define SPIDELAY_T2EDELAY_MASK  (0xFF << SPIDELAY_T2EDELAY_SHIFT)
#define SPIDELAY_C2EDELAY_SHIFT 0
#define SPIDELAY_C2EDELAY_MASK  0xFF

/* Error Masks */
#define SPIFLG_DLEN_ERR_MASK            BIT(0)
#define SPIFLG_TIMEOUT_MASK             BIT(1)
#define SPIFLG_PARERR_MASK              BIT(2)
#define SPIFLG_DESYNC_MASK              BIT(3)
#define SPIFLG_BITERR_MASK              BIT(4)
#define SPIFLG_OVRRUN_MASK              BIT(6)
#define SPIFLG_BUF_INIT_ACTIVE_MASK     BIT(24)
#define SPIFLG_ERROR_MASK               (SPIFLG_DLEN_ERR_MASK \
                                | SPIFLG_TIMEOUT_MASK | SPIFLG_PARERR_MASK \
                                | SPIFLG_DESYNC_MASK | SPIFLG_BITERR_MASK \
                                | SPIFLG_OVRRUN_MASK)

#define SPIINT_DMA_REQ_EN       BIT(16)

/* SPI Controller registers */
#define SPIGCR0         0x00
#define SPIGCR1         0x04
#define SPIINT          0x08
#define SPILVL          0x0c
#define SPIFLG          0x10
#define SPIPC0          0x14
#define SPIDAT1         0x3c
#define SPIBUF          0x40
#define SPIDELAY        0x48
#define SPIDEF          0x4c
#define SPIFMT0         0x50

/* We have 2 DMA channels per CS, one for RX and one for TX */
struct davinci_spi_dma {
        int                     tx_channel;
        int                     rx_channel;
        int                     dummy_param_slot;
        enum dma_event_q        eventq;
};

/* SPI Controller driver's private data. */
struct davinci_spi {
        struct spi_bitbang      bitbang;
        struct clk              *clk;

        u8                      version;
        resource_size_t         pbase;
        void __iomem            *base;
        u32                     irq;
        struct completion       done;

        const void              *tx;
        void                    *rx;
#define SPI_TMP_BUFSZ   (SMP_CACHE_BYTES + 1)
        u8                      rx_tmp_buf[SPI_TMP_BUFSZ];
        int                     rcount;
        int                     wcount;
        struct davinci_spi_dma  dma;
        struct davinci_spi_platform_data *pdata;

        void                    (*get_rx)(u32 rx_data, struct davinci_spi *);
        u32                     (*get_tx)(struct davinci_spi *);

        u8                      bytes_per_word[SPI_MAX_CHIPSELECT];
};

static struct davinci_spi_config davinci_spi_default_cfg;

static void davinci_spi_rx_buf_u8(u32 data, struct davinci_spi *dspi)
{
        if (dspi->rx) {
                u8 *rx = dspi->rx;
                *rx++ = (u8)data;
                dspi->rx = rx;
        }
}

static void davinci_spi_rx_buf_u16(u32 data, struct davinci_spi *dspi)
{
        if (dspi->rx) {
                u16 *rx = dspi->rx;
                *rx++ = (u16)data;
                dspi->rx = rx;
        }
}

static u32 davinci_spi_tx_buf_u8(struct davinci_spi *dspi)
{
        u32 data = 0;
        if (dspi->tx) {
                const u8 *tx = dspi->tx;
                data = *tx++;
                dspi->tx = tx;
        }
        return data;
}

static u32 davinci_spi_tx_buf_u16(struct davinci_spi *dspi)
{
        u32 data = 0;
        if (dspi->tx) {
                const u16 *tx = dspi->tx;
                data = *tx++;
                dspi->tx = tx;
        }
        return data;
}

static inline void set_io_bits(void __iomem *addr, u32 bits)
{
        u32 v = ioread32(addr);

        v |= bits;
        iowrite32(v, addr);
}

static inline void clear_io_bits(void __iomem *addr, u32 bits)
{
        u32 v = ioread32(addr);

        v &= ~bits;
        iowrite32(v, addr);
}

/*
 * Interface to control the chip select signal
 */
static void davinci_spi_chipselect(struct spi_device *spi, int value)
{
        struct davinci_spi *dspi;
        struct davinci_spi_platform_data *pdata;
        u8 chip_sel = spi->chip_select;
        u16 spidat1 = CS_DEFAULT;
        bool gpio_chipsel = false;

        dspi = spi_master_get_devdata(spi->master);
        pdata = dspi->pdata;

        if (pdata->chip_sel && chip_sel < pdata->num_chipselect &&
                                pdata->chip_sel[chip_sel] != SPI_INTERN_CS)
                gpio_chipsel = true;

        /*
         * Board specific chip select logic decides the polarity and cs
         * line for the controller
         */
        if (gpio_chipsel) {
                if (value == BITBANG_CS_ACTIVE)
                        gpio_set_value(pdata->chip_sel[chip_sel], 0);
                else
                        gpio_set_value(pdata->chip_sel[chip_sel], 1);
        } else {
                if (value == BITBANG_CS_ACTIVE) {
                        spidat1 |= SPIDAT1_CSHOLD_MASK;
                        spidat1 &= ~(0x1 << chip_sel);
                }

                iowrite16(spidat1, dspi->base + SPIDAT1 + 2);
        }
}

/**
 * davinci_spi_get_prescale - Calculates the correct prescale value
 * @maxspeed_hz: the maximum rate the SPI clock can run at
 *
 * This function calculates the prescale value that generates a clock rate
 * less than or equal to the specified maximum.
 *
 * Returns: calculated prescale - 1 for easy programming into SPI registers
 * or negative error number if valid prescalar cannot be updated.
 */
static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
                                                        u32 max_speed_hz)
{
        int ret;

        ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz);

        if (ret < 3 || ret > 256)
                return -EINVAL;

        return ret - 1;
}

/**
 * davinci_spi_setup_transfer - This functions will determine transfer method
 * @spi: spi device on which data transfer to be done
 * @t: spi transfer in which transfer info is filled
 *
 * This function determines data transfer method (8/16/32 bit transfer).
 * It will also set the SPI Clock Control register according to
 * SPI slave device freq.
 */
static int davinci_spi_setup_transfer(struct spi_device *spi,
                struct spi_transfer *t)
{

        struct davinci_spi *dspi;
        struct davinci_spi_config *spicfg;
        u8 bits_per_word = 0;
        u32 hz = 0, spifmt = 0, prescale = 0;

        dspi = spi_master_get_devdata(spi->master);
        spicfg = (struct davinci_spi_config *)spi->controller_data;
        if (!spicfg)
                spicfg = &davinci_spi_default_cfg;

        if (t) {
                bits_per_word = t->bits_per_word;
                hz = t->speed_hz;
        }

        /* if bits_per_word is not set then set it default */
        if (!bits_per_word)
                bits_per_word = spi->bits_per_word;

        /*
         * Assign function pointer to appropriate transfer method
         * 8bit, 16bit or 32bit transfer
         */
        if (bits_per_word <= 8 && bits_per_word >= 2) {
                dspi->get_rx = davinci_spi_rx_buf_u8;
                dspi->get_tx = davinci_spi_tx_buf_u8;
                dspi->bytes_per_word[spi->chip_select] = 1;
        } else if (bits_per_word <= 16 && bits_per_word >= 2) {
                dspi->get_rx = davinci_spi_rx_buf_u16;
                dspi->get_tx = davinci_spi_tx_buf_u16;
                dspi->bytes_per_word[spi->chip_select] = 2;
        } else
                return -EINVAL;

        if (!hz)
                hz = spi->max_speed_hz;

        /* Set up SPIFMTn register, unique to this chipselect. */

        prescale = davinci_spi_get_prescale(dspi, hz);
        if (prescale < 0)
                return prescale;

        spifmt = (prescale << SPIFMT_PRESCALE_SHIFT) | (bits_per_word & 0x1f);

        if (spi->mode & SPI_LSB_FIRST)
                spifmt |= SPIFMT_SHIFTDIR_MASK;

        if (spi->mode & SPI_CPOL)
                spifmt |= SPIFMT_POLARITY_MASK;

        if (!(spi->mode & SPI_CPHA))
                spifmt |= SPIFMT_PHASE_MASK;

        /*
         * Version 1 hardware supports two basic SPI modes:
         *  - Standard SPI mode uses 4 pins, with chipselect
         *  - 3 pin SPI is a 4 pin variant without CS (SPI_NO_CS)
         *      (distinct from SPI_3WIRE, with just one data wire;
         *      or similar variants without MOSI or without MISO)
         *
         * Version 2 hardware supports an optional handshaking signal,
         * so it can support two more modes:
         *  - 5 pin SPI variant is standard SPI plus SPI_READY
         *  - 4 pin with enable is (SPI_READY | SPI_NO_CS)
         */

        if (dspi->version == SPI_VERSION_2) {

                u32 delay = 0;

                spifmt |= ((spicfg->wdelay << SPIFMT_WDELAY_SHIFT)
                                                        & SPIFMT_WDELAY_MASK);

                if (spicfg->odd_parity)
                        spifmt |= SPIFMT_ODD_PARITY_MASK;

                if (spicfg->parity_enable)
                        spifmt |= SPIFMT_PARITYENA_MASK;

                if (spicfg->timer_disable) {
                        spifmt |= SPIFMT_DISTIMER_MASK;
                } else {
                        delay |= (spicfg->c2tdelay << SPIDELAY_C2TDELAY_SHIFT)
                                                & SPIDELAY_C2TDELAY_MASK;
                        delay |= (spicfg->t2cdelay << SPIDELAY_T2CDELAY_SHIFT)
                                                & SPIDELAY_T2CDELAY_MASK;
                }

                if (spi->mode & SPI_READY) {
                        spifmt |= SPIFMT_WAITENA_MASK;
                        delay |= (spicfg->t2edelay << SPIDELAY_T2EDELAY_SHIFT)
                                                & SPIDELAY_T2EDELAY_MASK;
                        delay |= (spicfg->c2edelay << SPIDELAY_C2EDELAY_SHIFT)
                                                & SPIDELAY_C2EDELAY_MASK;
                }

                iowrite32(delay, dspi->base + SPIDELAY);
        }

        iowrite32(spifmt, dspi->base + SPIFMT0);

        return 0;
}

/**
 * davinci_spi_setup - This functions will set default transfer method
 * @spi: spi device on which data transfer to be done
 *
 * This functions sets the default transfer method.
 */
static int davinci_spi_setup(struct spi_device *spi)
{
        int retval = 0;
        struct davinci_spi *dspi;
        struct davinci_spi_platform_data *pdata;

        dspi = spi_master_get_devdata(spi->master);
        pdata = dspi->pdata;

        /* if bits per word length is zero then set it default 8 */
        if (!spi->bits_per_word)
                spi->bits_per_word = 8;

        if (!(spi->mode & SPI_NO_CS)) {
                if ((pdata->chip_sel == NULL) ||
                    (pdata->chip_sel[spi->chip_select] == SPI_INTERN_CS))
                        set_io_bits(dspi->base + SPIPC0, 1 << spi->chip_select);

        }

        if (spi->mode & SPI_READY)
                set_io_bits(dspi->base + SPIPC0, SPIPC0_SPIENA_MASK);

        if (spi->mode & SPI_LOOP)
                set_io_bits(dspi->base + SPIGCR1, SPIGCR1_LOOPBACK_MASK);
        else
                clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_LOOPBACK_MASK);

        return retval;
}

static int davinci_spi_check_error(struct davinci_spi *dspi, int int_status)
{
        struct device *sdev = dspi->bitbang.master->dev.parent;

        if (int_status & SPIFLG_TIMEOUT_MASK) {
                dev_dbg(sdev, "SPI Time-out Error\n");
                return -ETIMEDOUT;
        }
        if (int_status & SPIFLG_DESYNC_MASK) {
                dev_dbg(sdev, "SPI Desynchronization Error\n");
                return -EIO;
        }
        if (int_status & SPIFLG_BITERR_MASK) {
                dev_dbg(sdev, "SPI Bit error\n");
                return -EIO;
        }

        if (dspi->version == SPI_VERSION_2) {
                if (int_status & SPIFLG_DLEN_ERR_MASK) {
                        dev_dbg(sdev, "SPI Data Length Error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_PARERR_MASK) {
                        dev_dbg(sdev, "SPI Parity Error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_OVRRUN_MASK) {
                        dev_dbg(sdev, "SPI Data Overrun error\n");
                        return -EIO;
                }
                if (int_status & SPIFLG_BUF_INIT_ACTIVE_MASK) {
                        dev_dbg(sdev, "SPI Buffer Init Active\n");
                        return -EBUSY;
                }
        }

        return 0;
}

/**
 * davinci_spi_process_events - check for and handle any SPI controller events
 * @dspi: the controller data
 *
 * This function will check the SPIFLG register and handle any events that are
 * detected there
 */
static int davinci_spi_process_events(struct davinci_spi *dspi)
{
        u32 buf, status, errors = 0, spidat1;

        buf = ioread32(dspi->base + SPIBUF);

        if (dspi->rcount > 0 && !(buf & SPIBUF_RXEMPTY_MASK)) {
                dspi->get_rx(buf & 0xFFFF, dspi);
                dspi->rcount--;
        }

        status = ioread32(dspi->base + SPIFLG);

        if (unlikely(status & SPIFLG_ERROR_MASK)) {
                errors = status & SPIFLG_ERROR_MASK;
                goto out;
        }

        if (dspi->wcount > 0 && !(buf & SPIBUF_TXFULL_MASK)) {
                spidat1 = ioread32(dspi->base + SPIDAT1);
                dspi->wcount--;
                spidat1 &= ~0xFFFF;
                spidat1 |= 0xFFFF & dspi->get_tx(dspi);
                iowrite32(spidat1, dspi->base + SPIDAT1);
        }

out:
        return errors;
}

static void davinci_spi_dma_callback(unsigned lch, u16 status, void *data)
{
        struct davinci_spi *dspi = data;
        struct davinci_spi_dma *dma = &dspi->dma;

        edma_stop(lch);

        if (status == DMA_COMPLETE) {
                if (lch == dma->rx_channel)
                        dspi->rcount = 0;
                if (lch == dma->tx_channel)
                        dspi->wcount = 0;
        }

        if ((!dspi->wcount && !dspi->rcount) || (status != DMA_COMPLETE))
                complete(&dspi->done);
}

/**
 * davinci_spi_bufs - functions which will handle transfer data
 * @spi: spi device on which data transfer to be done
 * @t: spi transfer in which transfer info is filled
 *
 * This function will put data to be transferred into data register
 * of SPI controller and then wait until the completion will be marked
 * by the IRQ Handler.
 */
static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
{
        struct davinci_spi *dspi;
        int data_type, ret;
        u32 tx_data, spidat1;
        u32 errors = 0;
        struct davinci_spi_config *spicfg;
        struct davinci_spi_platform_data *pdata;
        unsigned uninitialized_var(rx_buf_count);
        struct device *sdev;

        dspi = spi_master_get_devdata(spi->master);
        pdata = dspi->pdata;
        spicfg = (struct davinci_spi_config *)spi->controller_data;
        if (!spicfg)
                spicfg = &davinci_spi_default_cfg;
        sdev = dspi->bitbang.master->dev.parent;

        /* convert len to words based on bits_per_word */
        data_type = dspi->bytes_per_word[spi->chip_select];

        dspi->tx = t->tx_buf;
        dspi->rx = t->rx_buf;
        dspi->wcount = t->len / data_type;
        dspi->rcount = dspi->wcount;

        spidat1 = ioread32(dspi->base + SPIDAT1);

        clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);

        INIT_COMPLETION(dspi->done);

        if (spicfg->io_type == SPI_IO_TYPE_INTR)
                set_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);

        if (spicfg->io_type != SPI_IO_TYPE_DMA) {
                /* start the transfer */
                dspi->wcount--;
                tx_data = dspi->get_tx(dspi);
                spidat1 &= 0xFFFF0000;
                spidat1 |= tx_data & 0xFFFF;
                iowrite32(spidat1, dspi->base + SPIDAT1);
        } else {
                struct davinci_spi_dma *dma;
                unsigned long tx_reg, rx_reg;
                struct edmacc_param param;
                void *rx_buf;
                int b, c;

                dma = &dspi->dma;

                tx_reg = (unsigned long)dspi->pbase + SPIDAT1;
                rx_reg = (unsigned long)dspi->pbase + SPIBUF;

                /*
                 * Transmit DMA setup
                 *
                 * If there is transmit data, map the transmit buffer, set it
                 * as the source of data and set the source B index to data
                 * size. If there is no transmit data, set the transmit register
                 * as the source of data, and set the source B index to zero.
                 *
                 * The destination is always the transmit register itself. And
                 * the destination never increments.
                 */

                if (t->tx_buf) {
                        t->tx_dma = dma_map_single(&spi->dev, (void *)t->tx_buf,
                                                t->len, DMA_TO_DEVICE);
                        if (dma_mapping_error(&spi->dev, t->tx_dma)) {
                                dev_dbg(sdev, "Unable to DMA map %d bytes"
                                                "TX buffer\n", t->len);
                                return -ENOMEM;
                        }
                }

                /*
                 * If number of words is greater than 65535, then we need
                 * to configure a 3 dimension transfer.  Use the BCNTRLD
                 * feature to allow for transfers that aren't even multiples
                 * of 65535 (or any other possible b size) by first transferring
                 * the remainder amount then grabbing the next N blocks of
                 * 65535 words.
                 */

                c = dspi->wcount / (SZ_64K - 1);        /* N 65535 Blocks */
                b = dspi->wcount - c * (SZ_64K - 1);    /* Remainder */
                if (b)
                        c++;
                else
                        b = SZ_64K - 1;

                param.opt = TCINTEN | EDMA_TCC(dma->tx_channel);
                param.src = t->tx_buf ? t->tx_dma : tx_reg;
                param.a_b_cnt = b << 16 | data_type;
                param.dst = tx_reg;
                param.src_dst_bidx = t->tx_buf ? data_type : 0;
                param.link_bcntrld = 0xffffffff;
                param.src_dst_cidx = t->tx_buf ? data_type : 0;
                param.ccnt = c;
                edma_write_slot(dma->tx_channel, &param);
                edma_link(dma->tx_channel, dma->dummy_param_slot);

                /*
                 * Receive DMA setup
                 *
                 * If there is receive buffer, use it to receive data. If there
                 * is none provided, use a temporary receive buffer. Set the
                 * destination B index to 0 so effectively only one byte is used
                 * in the temporary buffer (address does not increment).
                 *
                 * The source of receive data is the receive data register. The
                 * source address never increments.
                 */

                if (t->rx_buf) {
                        rx_buf = t->rx_buf;
                        rx_buf_count = t->len;
                } else {
                        rx_buf = dspi->rx_tmp_buf;
                        rx_buf_count = sizeof(dspi->rx_tmp_buf);
                }

                t->rx_dma = dma_map_single(&spi->dev, rx_buf, rx_buf_count,
                                                        DMA_FROM_DEVICE);
                if (dma_mapping_error(&spi->dev, t->rx_dma)) {
                        dev_dbg(sdev, "Couldn't DMA map a %d bytes RX buffer\n",
                                                                rx_buf_count);
                        if (t->tx_buf)
                                dma_unmap_single(NULL, t->tx_dma, t->len,
                                                                DMA_TO_DEVICE);
                        return -ENOMEM;
                }

                param.opt = TCINTEN | EDMA_TCC(dma->rx_channel);
                param.src = rx_reg;
                param.a_b_cnt = b << 16 | data_type;
                param.dst = t->rx_dma;
                param.src_dst_bidx = (t->rx_buf ? data_type : 0) << 16;
                param.link_bcntrld = 0xffffffff;
                param.src_dst_cidx = (t->rx_buf ? data_type : 0) << 16;
                param.ccnt = c;
                edma_write_slot(dma->rx_channel, &param);

                if (pdata->cshold_bug)
                        iowrite16(spidat1 >> 16, dspi->base + SPIDAT1 + 2);

                edma_start(dma->rx_channel);
                edma_start(dma->tx_channel);
                set_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);
        }

        /* Wait for the transfer to complete */
        if (spicfg->io_type != SPI_IO_TYPE_POLL) {
                wait_for_completion_interruptible(&(dspi->done));
        } else {
                while (dspi->rcount > 0 || dspi->wcount > 0) {
                        errors = davinci_spi_process_events(dspi);
                        if (errors)
                                break;
                        cpu_relax();
                }
        }

        clear_io_bits(dspi->base + SPIINT, SPIINT_MASKALL);
        if (spicfg->io_type == SPI_IO_TYPE_DMA) {

                if (t->tx_buf)
                        dma_unmap_single(NULL, t->tx_dma, t->len,
                                                                DMA_TO_DEVICE);

                dma_unmap_single(NULL, t->rx_dma, rx_buf_count,
                                                        DMA_FROM_DEVICE);

                clear_io_bits(dspi->base + SPIINT, SPIINT_DMA_REQ_EN);
        }

        clear_io_bits(dspi->base + SPIGCR1, SPIGCR1_SPIENA_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);

        /*
         * Check for bit error, desync error,parity error,timeout error and
         * receive overflow errors
         */
        if (errors) {
                ret = davinci_spi_check_error(dspi, errors);
                WARN(!ret, "%s: error reported but no error found!\n",
                                                        dev_name(&spi->dev));
                return ret;
        }

        if (dspi->rcount != 0 || dspi->wcount != 0) {
                dev_err(sdev, "SPI data transfer error\n");
                return -EIO;
        }

        return t->len;
}

/**
 * davinci_spi_irq - Interrupt handler for SPI Master Controller
 * @irq: IRQ number for this SPI Master
 * @context_data: structure for SPI Master controller davinci_spi
 *
 * ISR will determine that interrupt arrives either for READ or WRITE command.
 * According to command it will do the appropriate action. It will check
 * transfer length and if it is not zero then dispatch transfer command again.
 * If transfer length is zero then it will indicate the COMPLETION so that
 * davinci_spi_bufs function can go ahead.
 */
static irqreturn_t davinci_spi_irq(s32 irq, void *data)
{
        struct davinci_spi *dspi = data;
        int status;

        status = davinci_spi_process_events(dspi);
        if (unlikely(status != 0))
                clear_io_bits(dspi->base + SPIINT, SPIINT_MASKINT);

        if ((!dspi->rcount && !dspi->wcount) || status)
                complete(&dspi->done);

        return IRQ_HANDLED;
}

static int davinci_spi_request_dma(struct davinci_spi *dspi)
{
        int r;
        struct davinci_spi_dma *dma = &dspi->dma;

        r = edma_alloc_channel(dma->rx_channel, davinci_spi_dma_callback, dspi,
                                                                dma->eventq);
        if (r < 0) {
                pr_err("Unable to request DMA channel for SPI RX\n");
                r = -EAGAIN;
                goto rx_dma_failed;
        }

        r = edma_alloc_channel(dma->tx_channel, davinci_spi_dma_callback, dspi,
                                                                dma->eventq);
        if (r < 0) {
                pr_err("Unable to request DMA channel for SPI TX\n");
                r = -EAGAIN;
                goto tx_dma_failed;
        }

        r = edma_alloc_slot(EDMA_CTLR(dma->tx_channel), EDMA_SLOT_ANY);
        if (r < 0) {
                pr_err("Unable to request SPI TX DMA param slot\n");
                r = -EAGAIN;
                goto param_failed;
        }
        dma->dummy_param_slot = r;
        edma_link(dma->dummy_param_slot, dma->dummy_param_slot);

        return 0;
param_failed:
        edma_free_channel(dma->tx_channel);
tx_dma_failed:
        edma_free_channel(dma->rx_channel);
rx_dma_failed:
        return r;
}

/**
 * davinci_spi_probe - probe function for SPI Master Controller
 * @pdev: platform_device structure which contains plateform specific data
 *
 * According to Linux Device Model this function will be invoked by Linux
 * with platform_device struct which contains the device specific info.
 * This function will map the SPI controller's memory, register IRQ,
 * Reset SPI controller and setting its registers to default value.
 * It will invoke spi_bitbang_start to create work queue so that client driver
 * can register transfer method to work queue.
 */
static int davinci_spi_probe(struct platform_device *pdev)
{
        struct spi_master *master;
        struct davinci_spi *dspi;
        struct davinci_spi_platform_data *pdata;
        struct resource *r, *mem;
        resource_size_t dma_rx_chan = SPI_NO_RESOURCE;
        resource_size_t dma_tx_chan = SPI_NO_RESOURCE;
        int i = 0, ret = 0;
        u32 spipc0;

        pdata = pdev->dev.platform_data;
        if (pdata == NULL) {
                ret = -ENODEV;
                goto err;
        }

        master = spi_alloc_master(&pdev->dev, sizeof(struct davinci_spi));
        if (master == NULL) {
                ret = -ENOMEM;
                goto err;
        }

        dev_set_drvdata(&pdev->dev, master);

        dspi = spi_master_get_devdata(master);
        if (dspi == NULL) {
                ret = -ENOENT;
                goto free_master;
        }

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (r == NULL) {
                ret = -ENOENT;
                goto free_master;
        }

        dspi->pbase = r->start;
        dspi->pdata = pdata;

        mem = request_mem_region(r->start, resource_size(r), pdev->name);
        if (mem == NULL) {
                ret = -EBUSY;
                goto free_master;
        }

        dspi->base = ioremap(r->start, resource_size(r));
        if (dspi->base == NULL) {
                ret = -ENOMEM;
                goto release_region;
        }

        dspi->irq = platform_get_irq(pdev, 0);
        if (dspi->irq <= 0) {
                ret = -EINVAL;
                goto unmap_io;
        }

        ret = request_irq(dspi->irq, davinci_spi_irq, 0, dev_name(&pdev->dev),
                                                                        dspi);
        if (ret)
                goto unmap_io;

        dspi->bitbang.master = spi_master_get(master);
        if (dspi->bitbang.master == NULL) {
                ret = -ENODEV;
                goto irq_free;
        }

        dspi->clk = clk_get(&pdev->dev, NULL);
        if (IS_ERR(dspi->clk)) {
                ret = -ENODEV;
                goto put_master;
        }
        clk_enable(dspi->clk);

        master->bus_num = pdev->id;
        master->num_chipselect = pdata->num_chipselect;
        master->setup = davinci_spi_setup;

        dspi->bitbang.chipselect = davinci_spi_chipselect;
        dspi->bitbang.setup_transfer = davinci_spi_setup_transfer;

        dspi->version = pdata->version;

        dspi->bitbang.flags = SPI_NO_CS | SPI_LSB_FIRST | SPI_LOOP;
        if (dspi->version == SPI_VERSION_2)
                dspi->bitbang.flags |= SPI_READY;

        r = platform_get_resource(pdev, IORESOURCE_DMA, 0);
        if (r)
                dma_rx_chan = r->start;
        r = platform_get_resource(pdev, IORESOURCE_DMA, 1);
        if (r)
                dma_tx_chan = r->start;

        dspi->bitbang.txrx_bufs = davinci_spi_bufs;
        if (dma_rx_chan != SPI_NO_RESOURCE &&
            dma_tx_chan != SPI_NO_RESOURCE) {
                dspi->dma.rx_channel = dma_rx_chan;
                dspi->dma.tx_channel = dma_tx_chan;
                dspi->dma.eventq = pdata->dma_event_q;

                ret = davinci_spi_request_dma(dspi);
                if (ret)
                        goto free_clk;

                dev_info(&pdev->dev, "DMA: supported\n");
                dev_info(&pdev->dev, "DMA: RX channel: %d, TX channel: %d, "
                                "event queue: %d\n", dma_rx_chan, dma_tx_chan,
                                pdata->dma_event_q);
        }

        dspi->get_rx = davinci_spi_rx_buf_u8;
        dspi->get_tx = davinci_spi_tx_buf_u8;

        init_completion(&dspi->done);

        /* Reset In/OUT SPI module */
        iowrite32(0, dspi->base + SPIGCR0);
        udelay(100);
        iowrite32(1, dspi->base + SPIGCR0);

        /* Set up SPIPC0.  CS and ENA init is done in davinci_spi_setup */
        spipc0 = SPIPC0_DIFUN_MASK | SPIPC0_DOFUN_MASK | SPIPC0_CLKFUN_MASK;
        iowrite32(spipc0, dspi->base + SPIPC0);

        /* initialize chip selects */
        if (pdata->chip_sel) {
                for (i = 0; i < pdata->num_chipselect; i++) {
                        if (pdata->chip_sel[i] != SPI_INTERN_CS)
                                gpio_direction_output(pdata->chip_sel[i], 1);
                }
        }

        if (pdata->intr_line)
                iowrite32(SPI_INTLVL_1, dspi->base + SPILVL);
        else
                iowrite32(SPI_INTLVL_0, dspi->base + SPILVL);

        iowrite32(CS_DEFAULT, dspi->base + SPIDEF);

        /* master mode default */
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_CLKMOD_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_MASTER_MASK);
        set_io_bits(dspi->base + SPIGCR1, SPIGCR1_POWERDOWN_MASK);

        ret = spi_bitbang_start(&dspi->bitbang);
        if (ret)
                goto free_dma;

        dev_info(&pdev->dev, "Controller at 0x%p\n", dspi->base);

        return ret;

free_dma:
        edma_free_channel(dspi->dma.tx_channel);
        edma_free_channel(dspi->dma.rx_channel);
        edma_free_slot(dspi->dma.dummy_param_slot);
free_clk:
        clk_disable(dspi->clk);
        clk_put(dspi->clk);
put_master:
        spi_master_put(master);
irq_free:
        free_irq(dspi->irq, dspi);
unmap_io:
        iounmap(dspi->base);
release_region:
        release_mem_region(dspi->pbase, resource_size(r));
free_master:
        kfree(master);
err:
        return ret;
}

/**
 * davinci_spi_remove - remove function for SPI Master Controller
 * @pdev: platform_device structure which contains plateform specific data
 *
 * This function will do the reverse action of davinci_spi_probe function
 * It will free the IRQ and SPI controller's memory region.
 * It will also call spi_bitbang_stop to destroy the work queue which was
 * created by spi_bitbang_start.
 */
static int __exit davinci_spi_remove(struct platform_device *pdev)
{
        struct davinci_spi *dspi;
        struct spi_master *master;
        struct resource *r;

        master = dev_get_drvdata(&pdev->dev);
        dspi = spi_master_get_devdata(master);

        spi_bitbang_stop(&dspi->bitbang);

        clk_disable(dspi->clk);
        clk_put(dspi->clk);
        spi_master_put(master);
        free_irq(dspi->irq, dspi);
        iounmap(dspi->base);
        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        release_mem_region(dspi->pbase, resource_size(r));

        return 0;
}

static struct platform_driver davinci_spi_driver = {
        .driver = {
                .name = "spi_davinci",
                .owner = THIS_MODULE,
        },
        .remove = __exit_p(davinci_spi_remove),
};

static int __init davinci_spi_init(void)
{
        return platform_driver_probe(&davinci_spi_driver, davinci_spi_probe);
}
module_init(davinci_spi_init);

static void __exit davinci_spi_exit(void)
{
        platform_driver_unregister(&davinci_spi_driver);
}
module_exit(davinci_spi_exit);

MODULE_DESCRIPTION("TI DaVinci SPI Master Controller Driver");
MODULE_LICENSE("GPL");