drivers/spi/mxs_spi.c - filogic/uboot - Gitiles

 /*
  * Freescale i.MX28 SPI driver
  *
  * Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
  * on behalf of DENX Software Engineering GmbH
  *
  * SPDX-License-Identifier:	GPL-2.0+
  *
  * NOTE: This driver only supports the SPI-controller chipselects,
  *       GPIO driven chipselects are not supported.
  */

 #include <common.h>
 #include <malloc.h>
 #include <spi.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/sys_proto.h>
 #include <asm/imx-common/dma.h>

 #define	MXS_SPI_MAX_TIMEOUT	1000000
 #define	MXS_SPI_PORT_OFFSET	0x2000
 #define MXS_SSP_CHIPSELECT_MASK		0x00300000
 #define MXS_SSP_CHIPSELECT_SHIFT	20

 #define MXSSSP_SMALL_TRANSFER	512

 struct mxs_spi_slave {
 	struct spi_slave	slave;
 	uint32_t		max_khz;
 	uint32_t		mode;
 	struct mxs_ssp_regs	*regs;
 };

 static inline struct mxs_spi_slave *to_mxs_slave(struct spi_slave *slave)
 {
 	return container_of(slave, struct mxs_spi_slave, slave);
 }

 void spi_init(void)
 {
 }

 int spi_cs_is_valid(unsigned int bus, unsigned int cs)
 {
 	/* MXS SPI: 4 ports and 3 chip selects maximum */
 	if (!mxs_ssp_bus_id_valid(bus) || cs > 2)
 		return 0;
 	else
 		return 1;
 }

 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 				  unsigned int max_hz, unsigned int mode)
 {
 	struct mxs_spi_slave *mxs_slave;
 	struct mxs_ssp_regs *ssp_regs;
 	int reg;

 	if (!spi_cs_is_valid(bus, cs)) {
 		printf("mxs_spi: invalid bus %d / chip select %d\n", bus, cs);
 		return NULL;
 	}

 	mxs_slave = spi_alloc_slave(struct mxs_spi_slave, bus, cs);
 	if (!mxs_slave)
 		return NULL;

 	if (mxs_dma_init_channel(MXS_DMA_CHANNEL_AHB_APBH_SSP0 + bus))
 		goto err_init;

 	mxs_slave->max_khz = max_hz / 1000;
 	mxs_slave->mode = mode;
 	mxs_slave->regs = mxs_ssp_regs_by_bus(bus);
 	ssp_regs = mxs_slave->regs;

 	reg = readl(&ssp_regs->hw_ssp_ctrl0);
 	reg &= ~(MXS_SSP_CHIPSELECT_MASK);
 	reg |= cs << MXS_SSP_CHIPSELECT_SHIFT;

 	writel(reg, &ssp_regs->hw_ssp_ctrl0);
 	return &mxs_slave->slave;

 err_init:
 	free(mxs_slave);
 	return NULL;
 }

 void spi_free_slave(struct spi_slave *slave)
 {
 	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
 	free(mxs_slave);
 }

 int spi_claim_bus(struct spi_slave *slave)
 {
 	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
 	struct mxs_ssp_regs *ssp_regs = mxs_slave->regs;
 	uint32_t reg = 0;

 	mxs_reset_block(&ssp_regs->hw_ssp_ctrl0_reg);

 	writel(SSP_CTRL0_BUS_WIDTH_ONE_BIT, &ssp_regs->hw_ssp_ctrl0);

 	reg = SSP_CTRL1_SSP_MODE_SPI | SSP_CTRL1_WORD_LENGTH_EIGHT_BITS;
 	reg |= (mxs_slave->mode & SPI_CPOL) ? SSP_CTRL1_POLARITY : 0;
 	reg |= (mxs_slave->mode & SPI_CPHA) ? SSP_CTRL1_PHASE : 0;
 	writel(reg, &ssp_regs->hw_ssp_ctrl1);

 	writel(0, &ssp_regs->hw_ssp_cmd0);

 	mxs_set_ssp_busclock(slave->bus, mxs_slave->max_khz);

 	return 0;
 }

 void spi_release_bus(struct spi_slave *slave)
 {
 }

 static void mxs_spi_start_xfer(struct mxs_ssp_regs *ssp_regs)
 {
 	writel(SSP_CTRL0_LOCK_CS, &ssp_regs->hw_ssp_ctrl0_set);
 	writel(SSP_CTRL0_IGNORE_CRC, &ssp_regs->hw_ssp_ctrl0_clr);
 }

 static void mxs_spi_end_xfer(struct mxs_ssp_regs *ssp_regs)
 {
 	writel(SSP_CTRL0_LOCK_CS, &ssp_regs->hw_ssp_ctrl0_clr);
 	writel(SSP_CTRL0_IGNORE_CRC, &ssp_regs->hw_ssp_ctrl0_set);
 }

 static int mxs_spi_xfer_pio(struct mxs_spi_slave *slave,
 			char *data, int length, int write, unsigned long flags)
 {
 	struct mxs_ssp_regs *ssp_regs = slave->regs;

 	if (flags & SPI_XFER_BEGIN)
 		mxs_spi_start_xfer(ssp_regs);

 	while (length--) {
 		/* We transfer 1 byte */
 #if defined(CONFIG_MX23)
 		writel(SSP_CTRL0_XFER_COUNT_MASK, &ssp_regs->hw_ssp_ctrl0_clr);
 		writel(1, &ssp_regs->hw_ssp_ctrl0_set);
 #elif defined(CONFIG_MX28)
 		writel(1, &ssp_regs->hw_ssp_xfer_size);
 #endif

 		if ((flags & SPI_XFER_END) && !length)
 			mxs_spi_end_xfer(ssp_regs);

 		if (write)
 			writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_clr);
 		else
 			writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_set);

 		writel(SSP_CTRL0_RUN, &ssp_regs->hw_ssp_ctrl0_set);

 		if (mxs_wait_mask_set(&ssp_regs->hw_ssp_ctrl0_reg,
 			SSP_CTRL0_RUN, MXS_SPI_MAX_TIMEOUT)) {
 			printf("MXS SPI: Timeout waiting for start\n");
 			return -ETIMEDOUT;
 		}

 		if (write)
 			writel(*data++, &ssp_regs->hw_ssp_data);

 		writel(SSP_CTRL0_DATA_XFER, &ssp_regs->hw_ssp_ctrl0_set);

 		if (!write) {
 			if (mxs_wait_mask_clr(&ssp_regs->hw_ssp_status_reg,
 				SSP_STATUS_FIFO_EMPTY, MXS_SPI_MAX_TIMEOUT)) {
 				printf("MXS SPI: Timeout waiting for data\n");
 				return -ETIMEDOUT;
 			}

 			*data = readl(&ssp_regs->hw_ssp_data);
 			data++;
 		}

 		if (mxs_wait_mask_clr(&ssp_regs->hw_ssp_ctrl0_reg,
 			SSP_CTRL0_RUN, MXS_SPI_MAX_TIMEOUT)) {
 			printf("MXS SPI: Timeout waiting for finish\n");
 			return -ETIMEDOUT;
 		}
 	}

 	return 0;
 }

 static int mxs_spi_xfer_dma(struct mxs_spi_slave *slave,
 			char *data, int length, int write, unsigned long flags)
 {
 	const int xfer_max_sz = 0xff00;
 	const int desc_count = DIV_ROUND_UP(length, xfer_max_sz) + 1;
 	struct mxs_ssp_regs *ssp_regs = slave->regs;
 	struct mxs_dma_desc *dp;
 	uint32_t ctrl0;
 	uint32_t cache_data_count;
 	const uint32_t dstart = (uint32_t)data;
 	int dmach;
 	int tl;
 	int ret = 0;

 #if defined(CONFIG_MX23)
 	const int mxs_spi_pio_words = 1;
 #elif defined(CONFIG_MX28)
 	const int mxs_spi_pio_words = 4;
 #endif

 	ALLOC_CACHE_ALIGN_BUFFER(struct mxs_dma_desc, desc, desc_count);

 	memset(desc, 0, sizeof(struct mxs_dma_desc) * desc_count);

 	ctrl0 = readl(&ssp_regs->hw_ssp_ctrl0);
 	ctrl0 |= SSP_CTRL0_DATA_XFER;

 	if (flags & SPI_XFER_BEGIN)
 		ctrl0 |= SSP_CTRL0_LOCK_CS;
 	if (!write)
 		ctrl0 |= SSP_CTRL0_READ;

 	if (length % ARCH_DMA_MINALIGN)
 		cache_data_count = roundup(length, ARCH_DMA_MINALIGN);
 	else
 		cache_data_count = length;

 	/* Flush data to DRAM so DMA can pick them up */
 	if (write)
 		flush_dcache_range(dstart, dstart + cache_data_count);

 	/* Invalidate the area, so no writeback into the RAM races with DMA */
 	invalidate_dcache_range(dstart, dstart + cache_data_count);

 	dmach = MXS_DMA_CHANNEL_AHB_APBH_SSP0 + slave->slave.bus;

 	dp = desc;
 	while (length) {
 		dp->address = (dma_addr_t)dp;
 		dp->cmd.address = (dma_addr_t)data;

 		/*
 		 * This is correct, even though it does indeed look insane.
 		 * I hereby have to, wholeheartedly, thank Freescale Inc.,
 		 * for always inventing insane hardware and keeping me busy
 		 * and employed ;-)
 		 */
 		if (write)
 			dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_READ;
 		else
 			dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_WRITE;

 		/*
 		 * The DMA controller can transfer large chunks (64kB) at
 		 * time by setting the transfer length to 0. Setting tl to
 		 * 0x10000 will overflow below and make .data contain 0.
 		 * Otherwise, 0xff00 is the transfer maximum.
 		 */
 		if (length >= 0x10000)
 			tl = 0x10000;
 		else
 			tl = min(length, xfer_max_sz);

 		dp->cmd.data |=
 			((tl & 0xffff) << MXS_DMA_DESC_BYTES_OFFSET) |
 			(mxs_spi_pio_words << MXS_DMA_DESC_PIO_WORDS_OFFSET) |
 			MXS_DMA_DESC_HALT_ON_TERMINATE |
 			MXS_DMA_DESC_TERMINATE_FLUSH;

 		data += tl;
 		length -= tl;

 		if (!length) {
 			dp->cmd.data |= MXS_DMA_DESC_IRQ | MXS_DMA_DESC_DEC_SEM;

 			if (flags & SPI_XFER_END) {
 				ctrl0 &= ~SSP_CTRL0_LOCK_CS;
 				ctrl0 |= SSP_CTRL0_IGNORE_CRC;
 			}
 		}

 		/*
 		 * Write CTRL0, CMD0, CMD1 and XFER_SIZE registers in
 		 * case of MX28, write only CTRL0 in case of MX23 due
 		 * to the difference in register layout. It is utterly
 		 * essential that the XFER_SIZE register is written on
 		 * a per-descriptor basis with the same size as is the
 		 * descriptor!
 		 */
 		dp->cmd.pio_words[0] = ctrl0;
 #ifdef CONFIG_MX28
 		dp->cmd.pio_words[1] = 0;
 		dp->cmd.pio_words[2] = 0;
 		dp->cmd.pio_words[3] = tl;
 #endif

 		mxs_dma_desc_append(dmach, dp);

 		dp++;
 	}

 	if (mxs_dma_go(dmach))
 		ret = -EINVAL;

 	/* The data arrived into DRAM, invalidate cache over them */
 	if (!write)
 		invalidate_dcache_range(dstart, dstart + cache_data_count);

 	return ret;
 }

 int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 		const void *dout, void *din, unsigned long flags)
 {
 	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
 	struct mxs_ssp_regs *ssp_regs = mxs_slave->regs;
 	int len = bitlen / 8;
 	char dummy;
 	int write = 0;
 	char *data = NULL;
 	int dma = 1;

 	if (bitlen == 0) {
 		if (flags & SPI_XFER_END) {
 			din = (void *)&dummy;
 			len = 1;
 		} else
 			return 0;
 	}

 	/* Half-duplex only */
 	if (din && dout)
 		return -EINVAL;
 	/* No data */
 	if (!din && !dout)
 		return 0;

 	if (dout) {
 		data = (char *)dout;
 		write = 1;
 	} else if (din) {
 		data = (char *)din;
 		write = 0;
 	}

 	/*
 	 * Check for alignment, if the buffer is aligned, do DMA transfer,
 	 * PIO otherwise. This is a temporary workaround until proper bounce
 	 * buffer is in place.
 	 */
 	if (dma) {
 		if (((uint32_t)data) & (ARCH_DMA_MINALIGN - 1))
 			dma = 0;
 		if (((uint32_t)len) & (ARCH_DMA_MINALIGN - 1))
 			dma = 0;
 	}

 	if (!dma || (len < MXSSSP_SMALL_TRANSFER)) {
 		writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_clr);
 		return mxs_spi_xfer_pio(mxs_slave, data, len, write, flags);
 	} else {
 		writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_set);
 		return mxs_spi_xfer_dma(mxs_slave, data, len, write, flags);
 	}
 }
	/*
	* Freescale i.MX28 SPI driver
	*
	* Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
	* on behalf of DENX Software Engineering GmbH
	*
	* SPDX-License-Identifier: GPL-2.0+
	*
	* NOTE: This driver only supports the SPI-controller chipselects,
	* GPIO driven chipselects are not supported.
	*/

	#include <common.h>
	#include <malloc.h>
	#include <spi.h>
	#include <asm/errno.h>
	#include <asm/io.h>
	#include <asm/arch/clock.h>
	#include <asm/arch/imx-regs.h>
	#include <asm/arch/sys_proto.h>
	#include <asm/imx-common/dma.h>

	#define MXS_SPI_MAX_TIMEOUT 1000000
	#define MXS_SPI_PORT_OFFSET 0x2000
	#define MXS_SSP_CHIPSELECT_MASK 0x00300000
	#define MXS_SSP_CHIPSELECT_SHIFT 20

	#define MXSSSP_SMALL_TRANSFER 512

	struct mxs_spi_slave {
	struct spi_slave slave;
	uint32_t max_khz;
	uint32_t mode;
	struct mxs_ssp_regs *regs;
	};

	static inline struct mxs_spi_slave to_mxs_slave(struct spi_slave slave)
	{
	return container_of(slave, struct mxs_spi_slave, slave);
	}

	void spi_init(void)
	{
	}

	int spi_cs_is_valid(unsigned int bus, unsigned int cs)
	{
	/* MXS SPI: 4 ports and 3 chip selects maximum */
	if (!mxs_ssp_bus_id_valid(bus) \|\| cs > 2)
	return 0;
	else
	return 1;
	}

	struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	struct mxs_spi_slave *mxs_slave;
	struct mxs_ssp_regs *ssp_regs;
	int reg;

	if (!spi_cs_is_valid(bus, cs)) {
	printf("mxs_spi: invalid bus %d / chip select %d\n", bus, cs);
	return NULL;
	}

	mxs_slave = spi_alloc_slave(struct mxs_spi_slave, bus, cs);
	if (!mxs_slave)
	return NULL;

	if (mxs_dma_init_channel(MXS_DMA_CHANNEL_AHB_APBH_SSP0 + bus))
	goto err_init;

	mxs_slave->max_khz = max_hz / 1000;
	mxs_slave->mode = mode;
	mxs_slave->regs = mxs_ssp_regs_by_bus(bus);
	ssp_regs = mxs_slave->regs;

	reg = readl(&ssp_regs->hw_ssp_ctrl0);
	reg &= ~(MXS_SSP_CHIPSELECT_MASK);
	reg \|= cs << MXS_SSP_CHIPSELECT_SHIFT;

	writel(reg, &ssp_regs->hw_ssp_ctrl0);
	return &mxs_slave->slave;

	err_init:
	free(mxs_slave);
	return NULL;
	}

	void spi_free_slave(struct spi_slave *slave)
	{
	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
	free(mxs_slave);
	}

	int spi_claim_bus(struct spi_slave *slave)
	{
	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
	struct mxs_ssp_regs *ssp_regs = mxs_slave->regs;
	uint32_t reg = 0;

	mxs_reset_block(&ssp_regs->hw_ssp_ctrl0_reg);

	writel(SSP_CTRL0_BUS_WIDTH_ONE_BIT, &ssp_regs->hw_ssp_ctrl0);

	reg = SSP_CTRL1_SSP_MODE_SPI \| SSP_CTRL1_WORD_LENGTH_EIGHT_BITS;
	reg \|= (mxs_slave->mode & SPI_CPOL) ? SSP_CTRL1_POLARITY : 0;
	reg \|= (mxs_slave->mode & SPI_CPHA) ? SSP_CTRL1_PHASE : 0;
	writel(reg, &ssp_regs->hw_ssp_ctrl1);

	writel(0, &ssp_regs->hw_ssp_cmd0);

	mxs_set_ssp_busclock(slave->bus, mxs_slave->max_khz);

	return 0;
	}

	void spi_release_bus(struct spi_slave *slave)
	{
	}

	static void mxs_spi_start_xfer(struct mxs_ssp_regs *ssp_regs)
	{
	writel(SSP_CTRL0_LOCK_CS, &ssp_regs->hw_ssp_ctrl0_set);
	writel(SSP_CTRL0_IGNORE_CRC, &ssp_regs->hw_ssp_ctrl0_clr);
	}

	static void mxs_spi_end_xfer(struct mxs_ssp_regs *ssp_regs)
	{
	writel(SSP_CTRL0_LOCK_CS, &ssp_regs->hw_ssp_ctrl0_clr);
	writel(SSP_CTRL0_IGNORE_CRC, &ssp_regs->hw_ssp_ctrl0_set);
	}

	static int mxs_spi_xfer_pio(struct mxs_spi_slave *slave,
	char *data, int length, int write, unsigned long flags)
	{
	struct mxs_ssp_regs *ssp_regs = slave->regs;

	if (flags & SPI_XFER_BEGIN)
	mxs_spi_start_xfer(ssp_regs);

	while (length--) {
	/* We transfer 1 byte */
	#if defined(CONFIG_MX23)
	writel(SSP_CTRL0_XFER_COUNT_MASK, &ssp_regs->hw_ssp_ctrl0_clr);
	writel(1, &ssp_regs->hw_ssp_ctrl0_set);
	#elif defined(CONFIG_MX28)
	writel(1, &ssp_regs->hw_ssp_xfer_size);
	#endif

	if ((flags & SPI_XFER_END) && !length)
	mxs_spi_end_xfer(ssp_regs);

	if (write)
	writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_clr);
	else
	writel(SSP_CTRL0_READ, &ssp_regs->hw_ssp_ctrl0_set);

	writel(SSP_CTRL0_RUN, &ssp_regs->hw_ssp_ctrl0_set);

	if (mxs_wait_mask_set(&ssp_regs->hw_ssp_ctrl0_reg,
	SSP_CTRL0_RUN, MXS_SPI_MAX_TIMEOUT)) {
	printf("MXS SPI: Timeout waiting for start\n");
	return -ETIMEDOUT;
	}

	if (write)
	writel(*data++, &ssp_regs->hw_ssp_data);

	writel(SSP_CTRL0_DATA_XFER, &ssp_regs->hw_ssp_ctrl0_set);

	if (!write) {
	if (mxs_wait_mask_clr(&ssp_regs->hw_ssp_status_reg,
	SSP_STATUS_FIFO_EMPTY, MXS_SPI_MAX_TIMEOUT)) {
	printf("MXS SPI: Timeout waiting for data\n");
	return -ETIMEDOUT;
	}

	*data = readl(&ssp_regs->hw_ssp_data);
	data++;
	}

	if (mxs_wait_mask_clr(&ssp_regs->hw_ssp_ctrl0_reg,
	SSP_CTRL0_RUN, MXS_SPI_MAX_TIMEOUT)) {
	printf("MXS SPI: Timeout waiting for finish\n");
	return -ETIMEDOUT;
	}
	}

	return 0;
	}

	static int mxs_spi_xfer_dma(struct mxs_spi_slave *slave,
	char *data, int length, int write, unsigned long flags)
	{
	const int xfer_max_sz = 0xff00;
	const int desc_count = DIV_ROUND_UP(length, xfer_max_sz) + 1;
	struct mxs_ssp_regs *ssp_regs = slave->regs;
	struct mxs_dma_desc *dp;
	uint32_t ctrl0;
	uint32_t cache_data_count;
	const uint32_t dstart = (uint32_t)data;
	int dmach;
	int tl;
	int ret = 0;

	#if defined(CONFIG_MX23)
	const int mxs_spi_pio_words = 1;
	#elif defined(CONFIG_MX28)
	const int mxs_spi_pio_words = 4;
	#endif

	ALLOC_CACHE_ALIGN_BUFFER(struct mxs_dma_desc, desc, desc_count);

	memset(desc, 0, sizeof(struct mxs_dma_desc) * desc_count);

	ctrl0 = readl(&ssp_regs->hw_ssp_ctrl0);
	ctrl0 \|= SSP_CTRL0_DATA_XFER;

	if (flags & SPI_XFER_BEGIN)
	ctrl0 \|= SSP_CTRL0_LOCK_CS;
	if (!write)
	ctrl0 \|= SSP_CTRL0_READ;

	if (length % ARCH_DMA_MINALIGN)
	cache_data_count = roundup(length, ARCH_DMA_MINALIGN);
	else
	cache_data_count = length;

	/* Flush data to DRAM so DMA can pick them up */
	if (write)
	flush_dcache_range(dstart, dstart + cache_data_count);

	/* Invalidate the area, so no writeback into the RAM races with DMA */
	invalidate_dcache_range(dstart, dstart + cache_data_count);

	dmach = MXS_DMA_CHANNEL_AHB_APBH_SSP0 + slave->slave.bus;

	dp = desc;
	while (length) {
	dp->address = (dma_addr_t)dp;
	dp->cmd.address = (dma_addr_t)data;

	/*
	* This is correct, even though it does indeed look insane.
	* I hereby have to, wholeheartedly, thank Freescale Inc.,
	* for always inventing insane hardware and keeping me busy
	* and employed ;-)
	*/
	if (write)
	dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_READ;
	else
	dp->cmd.data = MXS_DMA_DESC_COMMAND_DMA_WRITE;

	/*
	* The DMA controller can transfer large chunks (64kB) at
	* time by setting the transfer length to 0. Setting tl to
	* 0x10000 will overflow below and make .data contain 0.
	* Otherwise, 0xff00 is the transfer maximum.
	*/
	if (length >= 0x10000)
	tl = 0x10000;
	else
	tl = min(length, xfer_max_sz);

	dp->cmd.data \|=
	((tl & 0xffff) << MXS_DMA_DESC_BYTES_OFFSET) \|
	(mxs_spi_pio_words << MXS_DMA_DESC_PIO_WORDS_OFFSET) \|
	MXS_DMA_DESC_HALT_ON_TERMINATE \|
	MXS_DMA_DESC_TERMINATE_FLUSH;

	data += tl;
	length -= tl;

	if (!length) {
	dp->cmd.data \|= MXS_DMA_DESC_IRQ \| MXS_DMA_DESC_DEC_SEM;

	if (flags & SPI_XFER_END) {
	ctrl0 &= ~SSP_CTRL0_LOCK_CS;
	ctrl0 \|= SSP_CTRL0_IGNORE_CRC;
	}
	}

	/*
	* Write CTRL0, CMD0, CMD1 and XFER_SIZE registers in
	* case of MX28, write only CTRL0 in case of MX23 due
	* to the difference in register layout. It is utterly
	* essential that the XFER_SIZE register is written on
	* a per-descriptor basis with the same size as is the
	* descriptor!
	*/
	dp->cmd.pio_words[0] = ctrl0;
	#ifdef CONFIG_MX28
	dp->cmd.pio_words[1] = 0;
	dp->cmd.pio_words[2] = 0;
	dp->cmd.pio_words[3] = tl;
	#endif

	mxs_dma_desc_append(dmach, dp);

	dp++;
	}

	if (mxs_dma_go(dmach))
	ret = -EINVAL;

	/* The data arrived into DRAM, invalidate cache over them */
	if (!write)
	invalidate_dcache_range(dstart, dstart + cache_data_count);

	return ret;
	}

	int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
	const void dout, void din, unsigned long flags)
	{
	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
	struct mxs_ssp_regs *ssp_regs = mxs_slave->regs;
	int len = bitlen / 8;
	char dummy;
	int write = 0;
	char *data = NULL;
	int dma = 1;

	if (bitlen == 0) {
	if (flags & SPI_XFER_END) {
	din = (void *)&dummy;
	len = 1;
	} else
	return 0;
	}

	/* Half-duplex only */
	if (din && dout)
	return -EINVAL;
	/* No data */
	if (!din && !dout)
	return 0;

	if (dout) {
	data = (char *)dout;
	write = 1;
	} else if (din) {
	data = (char *)din;
	write = 0;
	}

	/*
	* Check for alignment, if the buffer is aligned, do DMA transfer,
	* PIO otherwise. This is a temporary workaround until proper bounce
	* buffer is in place.
	*/
	if (dma) {
	if (((uint32_t)data) & (ARCH_DMA_MINALIGN - 1))
	dma = 0;
	if (((uint32_t)len) & (ARCH_DMA_MINALIGN - 1))
	dma = 0;
	}

	if (!dma \|\| (len < MXSSSP_SMALL_TRANSFER)) {
	writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_clr);
	return mxs_spi_xfer_pio(mxs_slave, data, len, write, flags);
	} else {
	writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_set);
	return mxs_spi_xfer_dma(mxs_slave, data, len, write, flags);
	}
	}