drivers/spi/davinci_spi.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;

		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;
			}
		}

		param.opt = TCINTEN | EDMA_TCC(dma->tx_channel);
		param.src = t->tx_buf ? t->tx_dma : tx_reg;
		param.a_b_cnt = dspi->wcount << 16 | data_type;
		param.dst = tx_reg;
		param.src_dst_bidx = t->tx_buf ? data_type : 0;
		param.link_bcntrld = 0xffff;
		param.src_dst_cidx = 0;
		param.ccnt = 1;
		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 = dspi->rcount << 16 | data_type;
		param.dst = t->rx_dma;
		param.src_dst_bidx = (t->rx_buf ? data_type : 0) << 16;
		param.link_bcntrld = 0xffff;
		param.src_dst_cidx = 0;
		param.ccnt = 1;
		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;
	resource_size_t	dma_eventq = 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;
	r = platform_get_resource(pdev, IORESOURCE_DMA, 2);
	if (r)
		dma_eventq = r->start;

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

		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,
				dma_eventq);
	}

	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");