drivers/spi/spi-pxa2xx-pxadma.c - linux-mtk - Git at Google

 /*
  * PXA2xx SPI private DMA support.
  *
  * Copyright (C) 2005 Stephen Street / StreetFire Sound Labs
  *
  * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

 #include <linux/init.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/pxa2xx_ssp.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/pxa2xx_spi.h>

 #include "spi-pxa2xx.h"

 #define DMA_INT_MASK		(DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
 #define RESET_DMA_CHANNEL	(DCSR_NODESC | DMA_INT_MASK)

 bool pxa2xx_spi_dma_is_possible(size_t len)
 {
 	/* Try to map dma buffer and do a dma transfer if successful, but
 	 * only if the length is non-zero and less than MAX_DMA_LEN.
 	 *
 	 * Zero-length non-descriptor DMA is illegal on PXA2xx; force use
 	 * of PIO instead.  Care is needed above because the transfer may
 	 * have have been passed with buffers that are already dma mapped.
 	 * A zero-length transfer in PIO mode will not try to write/read
 	 * to/from the buffers
 	 *
 	 * REVISIT large transfers are exactly where we most want to be
 	 * using DMA.  If this happens much, split those transfers into
 	 * multiple DMA segments rather than forcing PIO.
 	 */
 	return len > 0 && len <= MAX_DMA_LEN;
 }

 int pxa2xx_spi_map_dma_buffers(struct driver_data *drv_data)
 {
 	struct spi_message *msg = drv_data->cur_msg;
 	struct device *dev = &msg->spi->dev;

 	if (!drv_data->cur_chip->enable_dma)
 		return 0;

 	if (msg->is_dma_mapped)
 		return  drv_data->rx_dma && drv_data->tx_dma;

 	if (!IS_DMA_ALIGNED(drv_data->rx) || !IS_DMA_ALIGNED(drv_data->tx))
 		return 0;

 	/* Modify setup if rx buffer is null */
 	if (drv_data->rx == NULL) {
 		*drv_data->null_dma_buf = 0;
 		drv_data->rx = drv_data->null_dma_buf;
 		drv_data->rx_map_len = 4;
 	} else
 		drv_data->rx_map_len = drv_data->len;


 	/* Modify setup if tx buffer is null */
 	if (drv_data->tx == NULL) {
 		*drv_data->null_dma_buf = 0;
 		drv_data->tx = drv_data->null_dma_buf;
 		drv_data->tx_map_len = 4;
 	} else
 		drv_data->tx_map_len = drv_data->len;

 	/* Stream map the tx buffer. Always do DMA_TO_DEVICE first
 	 * so we flush the cache *before* invalidating it, in case
 	 * the tx and rx buffers overlap.
 	 */
 	drv_data->tx_dma = dma_map_single(dev, drv_data->tx,
 					drv_data->tx_map_len, DMA_TO_DEVICE);
 	if (dma_mapping_error(dev, drv_data->tx_dma))
 		return 0;

 	/* Stream map the rx buffer */
 	drv_data->rx_dma = dma_map_single(dev, drv_data->rx,
 					drv_data->rx_map_len, DMA_FROM_DEVICE);
 	if (dma_mapping_error(dev, drv_data->rx_dma)) {
 		dma_unmap_single(dev, drv_data->tx_dma,
 					drv_data->tx_map_len, DMA_TO_DEVICE);
 		return 0;
 	}

 	return 1;
 }

 static void pxa2xx_spi_unmap_dma_buffers(struct driver_data *drv_data)
 {
 	struct device *dev;

 	if (!drv_data->dma_mapped)
 		return;

 	if (!drv_data->cur_msg->is_dma_mapped) {
 		dev = &drv_data->cur_msg->spi->dev;
 		dma_unmap_single(dev, drv_data->rx_dma,
 					drv_data->rx_map_len, DMA_FROM_DEVICE);
 		dma_unmap_single(dev, drv_data->tx_dma,
 					drv_data->tx_map_len, DMA_TO_DEVICE);
 	}

 	drv_data->dma_mapped = 0;
 }

 static int wait_ssp_rx_stall(void const __iomem *ioaddr)
 {
 	unsigned long limit = loops_per_jiffy << 1;

 	while ((read_SSSR(ioaddr) & SSSR_BSY) && --limit)
 		cpu_relax();

 	return limit;
 }

 static int wait_dma_channel_stop(int channel)
 {
 	unsigned long limit = loops_per_jiffy << 1;

 	while (!(DCSR(channel) & DCSR_STOPSTATE) && --limit)
 		cpu_relax();

 	return limit;
 }

 static void pxa2xx_spi_dma_error_stop(struct driver_data *drv_data,
 				      const char *msg)
 {
 	void __iomem *reg = drv_data->ioaddr;

 	/* Stop and reset */
 	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;
 	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
 	write_SSSR_CS(drv_data, drv_data->clear_sr);
 	write_SSCR1(read_SSCR1(reg) & ~drv_data->dma_cr1, reg);
 	if (!pxa25x_ssp_comp(drv_data))
 		write_SSTO(0, reg);
 	pxa2xx_spi_flush(drv_data);
 	write_SSCR0(read_SSCR0(reg) & ~SSCR0_SSE, reg);

 	pxa2xx_spi_unmap_dma_buffers(drv_data);

 	dev_err(&drv_data->pdev->dev, "%s\n", msg);

 	drv_data->cur_msg->state = ERROR_STATE;
 	tasklet_schedule(&drv_data->pump_transfers);
 }

 static void pxa2xx_spi_dma_transfer_complete(struct driver_data *drv_data)
 {
 	void __iomem *reg = drv_data->ioaddr;
 	struct spi_message *msg = drv_data->cur_msg;

 	/* Clear and disable interrupts on SSP and DMA channels*/
 	write_SSCR1(read_SSCR1(reg) & ~drv_data->dma_cr1, reg);
 	write_SSSR_CS(drv_data, drv_data->clear_sr);
 	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
 	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;

 	if (wait_dma_channel_stop(drv_data->rx_channel) == 0)
 		dev_err(&drv_data->pdev->dev,
 			"dma_handler: dma rx channel stop failed\n");

 	if (wait_ssp_rx_stall(drv_data->ioaddr) == 0)
 		dev_err(&drv_data->pdev->dev,
 			"dma_transfer: ssp rx stall failed\n");

 	pxa2xx_spi_unmap_dma_buffers(drv_data);

 	/* update the buffer pointer for the amount completed in dma */
 	drv_data->rx += drv_data->len -
 			(DCMD(drv_data->rx_channel) & DCMD_LENGTH);

 	/* read trailing data from fifo, it does not matter how many
 	 * bytes are in the fifo just read until buffer is full
 	 * or fifo is empty, which ever occurs first */
 	drv_data->read(drv_data);

 	/* return count of what was actually read */
 	msg->actual_length += drv_data->len -
 				(drv_data->rx_end - drv_data->rx);

 	/* Transfer delays and chip select release are
 	 * handled in pump_transfers or giveback
 	 */

 	/* Move to next transfer */
 	msg->state = pxa2xx_spi_next_transfer(drv_data);

 	/* Schedule transfer tasklet */
 	tasklet_schedule(&drv_data->pump_transfers);
 }

 void pxa2xx_spi_dma_handler(int channel, void *data)
 {
 	struct driver_data *drv_data = data;
 	u32 irq_status = DCSR(channel) & DMA_INT_MASK;

 	if (irq_status & DCSR_BUSERR) {

 		if (channel == drv_data->tx_channel)
 			pxa2xx_spi_dma_error_stop(drv_data,
 				"dma_handler: bad bus address on tx channel");
 		else
 			pxa2xx_spi_dma_error_stop(drv_data,
 				"dma_handler: bad bus address on rx channel");
 		return;
 	}

 	/* PXA255x_SSP has no timeout interrupt, wait for tailing bytes */
 	if ((channel == drv_data->tx_channel)
 		&& (irq_status & DCSR_ENDINTR)
 		&& (drv_data->ssp_type == PXA25x_SSP)) {

 		/* Wait for rx to stall */
 		if (wait_ssp_rx_stall(drv_data->ioaddr) == 0)
 			dev_err(&drv_data->pdev->dev,
 				"dma_handler: ssp rx stall failed\n");

 		/* finish this transfer, start the next */
 		pxa2xx_spi_dma_transfer_complete(drv_data);
 	}
 }

 irqreturn_t pxa2xx_spi_dma_transfer(struct driver_data *drv_data)
 {
 	u32 irq_status;
 	void __iomem *reg = drv_data->ioaddr;

 	irq_status = read_SSSR(reg) & drv_data->mask_sr;
 	if (irq_status & SSSR_ROR) {
 		pxa2xx_spi_dma_error_stop(drv_data,
 					  "dma_transfer: fifo overrun");
 		return IRQ_HANDLED;
 	}

 	/* Check for false positive timeout */
 	if ((irq_status & SSSR_TINT)
 		&& (DCSR(drv_data->tx_channel) & DCSR_RUN)) {
 		write_SSSR(SSSR_TINT, reg);
 		return IRQ_HANDLED;
 	}

 	if (irq_status & SSSR_TINT || drv_data->rx == drv_data->rx_end) {

 		/* Clear and disable timeout interrupt, do the rest in
 		 * dma_transfer_complete */
 		if (!pxa25x_ssp_comp(drv_data))
 			write_SSTO(0, reg);

 		/* finish this transfer, start the next */
 		pxa2xx_spi_dma_transfer_complete(drv_data);

 		return IRQ_HANDLED;
 	}

 	/* Opps problem detected */
 	return IRQ_NONE;
 }

 int pxa2xx_spi_dma_prepare(struct driver_data *drv_data, u32 dma_burst)
 {
 	u32 dma_width;

 	switch (drv_data->n_bytes) {
 	case 1:
 		dma_width = DCMD_WIDTH1;
 		break;
 	case 2:
 		dma_width = DCMD_WIDTH2;
 		break;
 	default:
 		dma_width = DCMD_WIDTH4;
 		break;
 	}

 	/* Setup rx DMA Channel */
 	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;
 	DSADR(drv_data->rx_channel) = drv_data->ssdr_physical;
 	DTADR(drv_data->rx_channel) = drv_data->rx_dma;
 	if (drv_data->rx == drv_data->null_dma_buf)
 		/* No target address increment */
 		DCMD(drv_data->rx_channel) = DCMD_FLOWSRC
 						| dma_width
 						| dma_burst
 						| drv_data->len;
 	else
 		DCMD(drv_data->rx_channel) = DCMD_INCTRGADDR
 						| DCMD_FLOWSRC
 						| dma_width
 						| dma_burst
 						| drv_data->len;

 	/* Setup tx DMA Channel */
 	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
 	DSADR(drv_data->tx_channel) = drv_data->tx_dma;
 	DTADR(drv_data->tx_channel) = drv_data->ssdr_physical;
 	if (drv_data->tx == drv_data->null_dma_buf)
 		/* No source address increment */
 		DCMD(drv_data->tx_channel) = DCMD_FLOWTRG
 						| dma_width
 						| dma_burst
 						| drv_data->len;
 	else
 		DCMD(drv_data->tx_channel) = DCMD_INCSRCADDR
 						| DCMD_FLOWTRG
 						| dma_width
 						| dma_burst
 						| drv_data->len;

 	/* Enable dma end irqs on SSP to detect end of transfer */
 	if (drv_data->ssp_type == PXA25x_SSP)
 		DCMD(drv_data->tx_channel) |= DCMD_ENDIRQEN;

 	return 0;
 }

 void pxa2xx_spi_dma_start(struct driver_data *drv_data)
 {
 	DCSR(drv_data->rx_channel) |= DCSR_RUN;
 	DCSR(drv_data->tx_channel) |= DCSR_RUN;
 }

 int pxa2xx_spi_dma_setup(struct driver_data *drv_data)
 {
 	struct device *dev = &drv_data->pdev->dev;
 	struct ssp_device *ssp = drv_data->ssp;

 	/* Get two DMA channels	(rx and tx) */
 	drv_data->rx_channel = pxa_request_dma("pxa2xx_spi_ssp_rx",
 						DMA_PRIO_HIGH,
 						pxa2xx_spi_dma_handler,
 						drv_data);
 	if (drv_data->rx_channel < 0) {
 		dev_err(dev, "problem (%d) requesting rx channel\n",
 			drv_data->rx_channel);
 		return -ENODEV;
 	}
 	drv_data->tx_channel = pxa_request_dma("pxa2xx_spi_ssp_tx",
 						DMA_PRIO_MEDIUM,
 						pxa2xx_spi_dma_handler,
 						drv_data);
 	if (drv_data->tx_channel < 0) {
 		dev_err(dev, "problem (%d) requesting tx channel\n",
 			drv_data->tx_channel);
 		pxa_free_dma(drv_data->rx_channel);
 		return -ENODEV;
 	}

 	DRCMR(ssp->drcmr_rx) = DRCMR_MAPVLD | drv_data->rx_channel;
 	DRCMR(ssp->drcmr_tx) = DRCMR_MAPVLD | drv_data->tx_channel;

 	return 0;
 }

 void pxa2xx_spi_dma_release(struct driver_data *drv_data)
 {
 	struct ssp_device *ssp = drv_data->ssp;

 	DRCMR(ssp->drcmr_rx) = 0;
 	DRCMR(ssp->drcmr_tx) = 0;

 	if (drv_data->tx_channel != 0)
 		pxa_free_dma(drv_data->tx_channel);
 	if (drv_data->rx_channel != 0)
 		pxa_free_dma(drv_data->rx_channel);
 }

 void pxa2xx_spi_dma_resume(struct driver_data *drv_data)
 {
 	if (drv_data->rx_channel != -1)
 		DRCMR(drv_data->ssp->drcmr_rx) =
 			DRCMR_MAPVLD | drv_data->rx_channel;
 	if (drv_data->tx_channel != -1)
 		DRCMR(drv_data->ssp->drcmr_tx) =
 			DRCMR_MAPVLD | drv_data->tx_channel;
 }

 int pxa2xx_spi_set_dma_burst_and_threshold(struct chip_data *chip,
 					   struct spi_device *spi,
 					   u8 bits_per_word, u32 *burst_code,
 					   u32 *threshold)
 {
 	struct pxa2xx_spi_chip *chip_info =
 			(struct pxa2xx_spi_chip *)spi->controller_data;
 	int bytes_per_word;
 	int burst_bytes;
 	int thresh_words;
 	int req_burst_size;
 	int retval = 0;

 	/* Set the threshold (in registers) to equal the same amount of data
 	 * as represented by burst size (in bytes).  The computation below
 	 * is (burst_size rounded up to nearest 8 byte, word or long word)
 	 * divided by (bytes/register); the tx threshold is the inverse of
 	 * the rx, so that there will always be enough data in the rx fifo
 	 * to satisfy a burst, and there will always be enough space in the
 	 * tx fifo to accept a burst (a tx burst will overwrite the fifo if
 	 * there is not enough space), there must always remain enough empty
 	 * space in the rx fifo for any data loaded to the tx fifo.
 	 * Whenever burst_size (in bytes) equals bits/word, the fifo threshold
 	 * will be 8, or half the fifo;
 	 * The threshold can only be set to 2, 4 or 8, but not 16, because
 	 * to burst 16 to the tx fifo, the fifo would have to be empty;
 	 * however, the minimum fifo trigger level is 1, and the tx will
 	 * request service when the fifo is at this level, with only 15 spaces.
 	 */

 	/* find bytes/word */
 	if (bits_per_word <= 8)
 		bytes_per_word = 1;
 	else if (bits_per_word <= 16)
 		bytes_per_word = 2;
 	else
 		bytes_per_word = 4;

 	/* use struct pxa2xx_spi_chip->dma_burst_size if available */
 	if (chip_info)
 		req_burst_size = chip_info->dma_burst_size;
 	else {
 		switch (chip->dma_burst_size) {
 		default:
 			/* if the default burst size is not set,
 			 * do it now */
 			chip->dma_burst_size = DCMD_BURST8;
 		case DCMD_BURST8:
 			req_burst_size = 8;
 			break;
 		case DCMD_BURST16:
 			req_burst_size = 16;
 			break;
 		case DCMD_BURST32:
 			req_burst_size = 32;
 			break;
 		}
 	}
 	if (req_burst_size <= 8) {
 		*burst_code = DCMD_BURST8;
 		burst_bytes = 8;
 	} else if (req_burst_size <= 16) {
 		if (bytes_per_word == 1) {
 			/* don't burst more than 1/2 the fifo */
 			*burst_code = DCMD_BURST8;
 			burst_bytes = 8;
 			retval = 1;
 		} else {
 			*burst_code = DCMD_BURST16;
 			burst_bytes = 16;
 		}
 	} else {
 		if (bytes_per_word == 1) {
 			/* don't burst more than 1/2 the fifo */
 			*burst_code = DCMD_BURST8;
 			burst_bytes = 8;
 			retval = 1;
 		} else if (bytes_per_word == 2) {
 			/* don't burst more than 1/2 the fifo */
 			*burst_code = DCMD_BURST16;
 			burst_bytes = 16;
 			retval = 1;
 		} else {
 			*burst_code = DCMD_BURST32;
 			burst_bytes = 32;
 		}
 	}

 	thresh_words = burst_bytes / bytes_per_word;

 	/* thresh_words will be between 2 and 8 */
 	*threshold = (SSCR1_RxTresh(thresh_words) & SSCR1_RFT)
 			| (SSCR1_TxTresh(16-thresh_words) & SSCR1_TFT);

 	return retval;
 }
	/*
	* PXA2xx SPI private DMA support.
	*
	* Copyright (C) 2005 Stephen Street / StreetFire Sound Labs
	*
	* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
	*/

	#include <linux/init.h>
	#include <linux/delay.h>
	#include <linux/device.h>
	#include <linux/dma-mapping.h>
	#include <linux/pxa2xx_ssp.h>
	#include <linux/spi/spi.h>
	#include <linux/spi/pxa2xx_spi.h>

	#include "spi-pxa2xx.h"

	#define DMA_INT_MASK (DCSR_ENDINTR \| DCSR_STARTINTR \| DCSR_BUSERR)
	#define RESET_DMA_CHANNEL (DCSR_NODESC \| DMA_INT_MASK)

	bool pxa2xx_spi_dma_is_possible(size_t len)
	{
	/* Try to map dma buffer and do a dma transfer if successful, but
	* only if the length is non-zero and less than MAX_DMA_LEN.
	*
	* Zero-length non-descriptor DMA is illegal on PXA2xx; force use
	* of PIO instead. Care is needed above because the transfer may
	* have have been passed with buffers that are already dma mapped.
	* A zero-length transfer in PIO mode will not try to write/read
	* to/from the buffers
	*
	* REVISIT large transfers are exactly where we most want to be
	* using DMA. If this happens much, split those transfers into
	* multiple DMA segments rather than forcing PIO.
	*/
	return len > 0 && len <= MAX_DMA_LEN;
	}

	int pxa2xx_spi_map_dma_buffers(struct driver_data *drv_data)
	{
	struct spi_message *msg = drv_data->cur_msg;
	struct device *dev = &msg->spi->dev;

	if (!drv_data->cur_chip->enable_dma)
	return 0;

	if (msg->is_dma_mapped)
	return drv_data->rx_dma && drv_data->tx_dma;

	if (!IS_DMA_ALIGNED(drv_data->rx) \|\| !IS_DMA_ALIGNED(drv_data->tx))
	return 0;

	/* Modify setup if rx buffer is null */
	if (drv_data->rx == NULL) {
	*drv_data->null_dma_buf = 0;
	drv_data->rx = drv_data->null_dma_buf;
	drv_data->rx_map_len = 4;
	} else
	drv_data->rx_map_len = drv_data->len;


	/* Modify setup if tx buffer is null */
	if (drv_data->tx == NULL) {
	*drv_data->null_dma_buf = 0;
	drv_data->tx = drv_data->null_dma_buf;
	drv_data->tx_map_len = 4;
	} else
	drv_data->tx_map_len = drv_data->len;

	/* Stream map the tx buffer. Always do DMA_TO_DEVICE first
	* so we flush the cache before invalidating it, in case
	* the tx and rx buffers overlap.
	*/
	drv_data->tx_dma = dma_map_single(dev, drv_data->tx,
	drv_data->tx_map_len, DMA_TO_DEVICE);
	if (dma_mapping_error(dev, drv_data->tx_dma))
	return 0;

	/* Stream map the rx buffer */
	drv_data->rx_dma = dma_map_single(dev, drv_data->rx,
	drv_data->rx_map_len, DMA_FROM_DEVICE);
	if (dma_mapping_error(dev, drv_data->rx_dma)) {
	dma_unmap_single(dev, drv_data->tx_dma,
	drv_data->tx_map_len, DMA_TO_DEVICE);
	return 0;
	}

	return 1;
	}

	static void pxa2xx_spi_unmap_dma_buffers(struct driver_data *drv_data)
	{
	struct device *dev;

	if (!drv_data->dma_mapped)
	return;

	if (!drv_data->cur_msg->is_dma_mapped) {
	dev = &drv_data->cur_msg->spi->dev;
	dma_unmap_single(dev, drv_data->rx_dma,
	drv_data->rx_map_len, DMA_FROM_DEVICE);
	dma_unmap_single(dev, drv_data->tx_dma,
	drv_data->tx_map_len, DMA_TO_DEVICE);
	}

	drv_data->dma_mapped = 0;
	}

	static int wait_ssp_rx_stall(void const __iomem *ioaddr)
	{
	unsigned long limit = loops_per_jiffy << 1;

	while ((read_SSSR(ioaddr) & SSSR_BSY) && --limit)
	cpu_relax();

	return limit;
	}

	static int wait_dma_channel_stop(int channel)
	{
	unsigned long limit = loops_per_jiffy << 1;

	while (!(DCSR(channel) & DCSR_STOPSTATE) && --limit)
	cpu_relax();

	return limit;
	}

	static void pxa2xx_spi_dma_error_stop(struct driver_data *drv_data,
	const char *msg)
	{
	void __iomem *reg = drv_data->ioaddr;

	/* Stop and reset */
	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;
	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
	write_SSSR_CS(drv_data, drv_data->clear_sr);
	write_SSCR1(read_SSCR1(reg) & ~drv_data->dma_cr1, reg);
	if (!pxa25x_ssp_comp(drv_data))
	write_SSTO(0, reg);
	pxa2xx_spi_flush(drv_data);
	write_SSCR0(read_SSCR0(reg) & ~SSCR0_SSE, reg);

	pxa2xx_spi_unmap_dma_buffers(drv_data);

	dev_err(&drv_data->pdev->dev, "%s\n", msg);

	drv_data->cur_msg->state = ERROR_STATE;
	tasklet_schedule(&drv_data->pump_transfers);
	}

	static void pxa2xx_spi_dma_transfer_complete(struct driver_data *drv_data)
	{
	void __iomem *reg = drv_data->ioaddr;
	struct spi_message *msg = drv_data->cur_msg;

	/* Clear and disable interrupts on SSP and DMA channels*/
	write_SSCR1(read_SSCR1(reg) & ~drv_data->dma_cr1, reg);
	write_SSSR_CS(drv_data, drv_data->clear_sr);
	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;

	if (wait_dma_channel_stop(drv_data->rx_channel) == 0)
	dev_err(&drv_data->pdev->dev,
	"dma_handler: dma rx channel stop failed\n");

	if (wait_ssp_rx_stall(drv_data->ioaddr) == 0)
	dev_err(&drv_data->pdev->dev,
	"dma_transfer: ssp rx stall failed\n");

	pxa2xx_spi_unmap_dma_buffers(drv_data);

	/* update the buffer pointer for the amount completed in dma */
	drv_data->rx += drv_data->len -
	(DCMD(drv_data->rx_channel) & DCMD_LENGTH);

	/* read trailing data from fifo, it does not matter how many
	* bytes are in the fifo just read until buffer is full
	* or fifo is empty, which ever occurs first */
	drv_data->read(drv_data);

	/* return count of what was actually read */
	msg->actual_length += drv_data->len -
	(drv_data->rx_end - drv_data->rx);

	/* Transfer delays and chip select release are
	* handled in pump_transfers or giveback
	*/

	/* Move to next transfer */
	msg->state = pxa2xx_spi_next_transfer(drv_data);

	/* Schedule transfer tasklet */
	tasklet_schedule(&drv_data->pump_transfers);
	}

	void pxa2xx_spi_dma_handler(int channel, void *data)
	{
	struct driver_data *drv_data = data;
	u32 irq_status = DCSR(channel) & DMA_INT_MASK;

	if (irq_status & DCSR_BUSERR) {

	if (channel == drv_data->tx_channel)
	pxa2xx_spi_dma_error_stop(drv_data,
	"dma_handler: bad bus address on tx channel");
	else
	pxa2xx_spi_dma_error_stop(drv_data,
	"dma_handler: bad bus address on rx channel");
	return;
	}

	/* PXA255x_SSP has no timeout interrupt, wait for tailing bytes */
	if ((channel == drv_data->tx_channel)
	&& (irq_status & DCSR_ENDINTR)
	&& (drv_data->ssp_type == PXA25x_SSP)) {

	/* Wait for rx to stall */
	if (wait_ssp_rx_stall(drv_data->ioaddr) == 0)
	dev_err(&drv_data->pdev->dev,
	"dma_handler: ssp rx stall failed\n");

	/* finish this transfer, start the next */
	pxa2xx_spi_dma_transfer_complete(drv_data);
	}
	}

	irqreturn_t pxa2xx_spi_dma_transfer(struct driver_data *drv_data)
	{
	u32 irq_status;
	void __iomem *reg = drv_data->ioaddr;

	irq_status = read_SSSR(reg) & drv_data->mask_sr;
	if (irq_status & SSSR_ROR) {
	pxa2xx_spi_dma_error_stop(drv_data,
	"dma_transfer: fifo overrun");
	return IRQ_HANDLED;
	}

	/* Check for false positive timeout */
	if ((irq_status & SSSR_TINT)
	&& (DCSR(drv_data->tx_channel) & DCSR_RUN)) {
	write_SSSR(SSSR_TINT, reg);
	return IRQ_HANDLED;
	}

	if (irq_status & SSSR_TINT \|\| drv_data->rx == drv_data->rx_end) {

	/* Clear and disable timeout interrupt, do the rest in
	* dma_transfer_complete */
	if (!pxa25x_ssp_comp(drv_data))
	write_SSTO(0, reg);

	/* finish this transfer, start the next */
	pxa2xx_spi_dma_transfer_complete(drv_data);

	return IRQ_HANDLED;
	}

	/* Opps problem detected */
	return IRQ_NONE;
	}

	int pxa2xx_spi_dma_prepare(struct driver_data *drv_data, u32 dma_burst)
	{
	u32 dma_width;

	switch (drv_data->n_bytes) {
	case 1:
	dma_width = DCMD_WIDTH1;
	break;
	case 2:
	dma_width = DCMD_WIDTH2;
	break;
	default:
	dma_width = DCMD_WIDTH4;
	break;
	}

	/* Setup rx DMA Channel */
	DCSR(drv_data->rx_channel) = RESET_DMA_CHANNEL;
	DSADR(drv_data->rx_channel) = drv_data->ssdr_physical;
	DTADR(drv_data->rx_channel) = drv_data->rx_dma;
	if (drv_data->rx == drv_data->null_dma_buf)
	/* No target address increment */
	DCMD(drv_data->rx_channel) = DCMD_FLOWSRC
	\| dma_width
	\| dma_burst
	\| drv_data->len;
	else
	DCMD(drv_data->rx_channel) = DCMD_INCTRGADDR
	\| DCMD_FLOWSRC
	\| dma_width
	\| dma_burst
	\| drv_data->len;

	/* Setup tx DMA Channel */
	DCSR(drv_data->tx_channel) = RESET_DMA_CHANNEL;
	DSADR(drv_data->tx_channel) = drv_data->tx_dma;
	DTADR(drv_data->tx_channel) = drv_data->ssdr_physical;
	if (drv_data->tx == drv_data->null_dma_buf)
	/* No source address increment */
	DCMD(drv_data->tx_channel) = DCMD_FLOWTRG
	\| dma_width
	\| dma_burst
	\| drv_data->len;
	else
	DCMD(drv_data->tx_channel) = DCMD_INCSRCADDR
	\| DCMD_FLOWTRG
	\| dma_width
	\| dma_burst
	\| drv_data->len;

	/* Enable dma end irqs on SSP to detect end of transfer */
	if (drv_data->ssp_type == PXA25x_SSP)
	DCMD(drv_data->tx_channel) \|= DCMD_ENDIRQEN;

	return 0;
	}

	void pxa2xx_spi_dma_start(struct driver_data *drv_data)
	{
	DCSR(drv_data->rx_channel) \|= DCSR_RUN;
	DCSR(drv_data->tx_channel) \|= DCSR_RUN;
	}

	int pxa2xx_spi_dma_setup(struct driver_data *drv_data)
	{
	struct device *dev = &drv_data->pdev->dev;
	struct ssp_device *ssp = drv_data->ssp;

	/* Get two DMA channels (rx and tx) */
	drv_data->rx_channel = pxa_request_dma("pxa2xx_spi_ssp_rx",
	DMA_PRIO_HIGH,
	pxa2xx_spi_dma_handler,
	drv_data);
	if (drv_data->rx_channel < 0) {
	dev_err(dev, "problem (%d) requesting rx channel\n",
	drv_data->rx_channel);
	return -ENODEV;
	}
	drv_data->tx_channel = pxa_request_dma("pxa2xx_spi_ssp_tx",
	DMA_PRIO_MEDIUM,
	pxa2xx_spi_dma_handler,
	drv_data);
	if (drv_data->tx_channel < 0) {
	dev_err(dev, "problem (%d) requesting tx channel\n",
	drv_data->tx_channel);
	pxa_free_dma(drv_data->rx_channel);
	return -ENODEV;
	}

	DRCMR(ssp->drcmr_rx) = DRCMR_MAPVLD \| drv_data->rx_channel;
	DRCMR(ssp->drcmr_tx) = DRCMR_MAPVLD \| drv_data->tx_channel;

	return 0;
	}

	void pxa2xx_spi_dma_release(struct driver_data *drv_data)
	{
	struct ssp_device *ssp = drv_data->ssp;

	DRCMR(ssp->drcmr_rx) = 0;
	DRCMR(ssp->drcmr_tx) = 0;

	if (drv_data->tx_channel != 0)
	pxa_free_dma(drv_data->tx_channel);
	if (drv_data->rx_channel != 0)
	pxa_free_dma(drv_data->rx_channel);
	}

	void pxa2xx_spi_dma_resume(struct driver_data *drv_data)
	{
	if (drv_data->rx_channel != -1)
	DRCMR(drv_data->ssp->drcmr_rx) =
	DRCMR_MAPVLD \| drv_data->rx_channel;
	if (drv_data->tx_channel != -1)
	DRCMR(drv_data->ssp->drcmr_tx) =
	DRCMR_MAPVLD \| drv_data->tx_channel;
	}

	int pxa2xx_spi_set_dma_burst_and_threshold(struct chip_data *chip,
	struct spi_device *spi,
	u8 bits_per_word, u32 *burst_code,
	u32 *threshold)
	{
	struct pxa2xx_spi_chip *chip_info =
	(struct pxa2xx_spi_chip *)spi->controller_data;
	int bytes_per_word;
	int burst_bytes;
	int thresh_words;
	int req_burst_size;
	int retval = 0;

	/* Set the threshold (in registers) to equal the same amount of data
	* as represented by burst size (in bytes). The computation below
	* is (burst_size rounded up to nearest 8 byte, word or long word)
	* divided by (bytes/register); the tx threshold is the inverse of
	* the rx, so that there will always be enough data in the rx fifo
	* to satisfy a burst, and there will always be enough space in the
	* tx fifo to accept a burst (a tx burst will overwrite the fifo if
	* there is not enough space), there must always remain enough empty
	* space in the rx fifo for any data loaded to the tx fifo.
	* Whenever burst_size (in bytes) equals bits/word, the fifo threshold
	* will be 8, or half the fifo;
	* The threshold can only be set to 2, 4 or 8, but not 16, because
	* to burst 16 to the tx fifo, the fifo would have to be empty;
	* however, the minimum fifo trigger level is 1, and the tx will
	* request service when the fifo is at this level, with only 15 spaces.
	*/

	/* find bytes/word */
	if (bits_per_word <= 8)
	bytes_per_word = 1;
	else if (bits_per_word <= 16)
	bytes_per_word = 2;
	else
	bytes_per_word = 4;

	/* use struct pxa2xx_spi_chip->dma_burst_size if available */
	if (chip_info)
	req_burst_size = chip_info->dma_burst_size;
	else {
	switch (chip->dma_burst_size) {
	default:
	/* if the default burst size is not set,
	* do it now */
	chip->dma_burst_size = DCMD_BURST8;
	case DCMD_BURST8:
	req_burst_size = 8;
	break;
	case DCMD_BURST16:
	req_burst_size = 16;
	break;
	case DCMD_BURST32:
	req_burst_size = 32;
	break;
	}
	}
	if (req_burst_size <= 8) {
	*burst_code = DCMD_BURST8;
	burst_bytes = 8;
	} else if (req_burst_size <= 16) {
	if (bytes_per_word == 1) {
	/* don't burst more than 1/2 the fifo */
	*burst_code = DCMD_BURST8;
	burst_bytes = 8;
	retval = 1;
	} else {
	*burst_code = DCMD_BURST16;
	burst_bytes = 16;
	}
	} else {
	if (bytes_per_word == 1) {
	/* don't burst more than 1/2 the fifo */
	*burst_code = DCMD_BURST8;
	burst_bytes = 8;
	retval = 1;
	} else if (bytes_per_word == 2) {
	/* don't burst more than 1/2 the fifo */
	*burst_code = DCMD_BURST16;
	burst_bytes = 16;
	retval = 1;
	} else {
	*burst_code = DCMD_BURST32;
	burst_bytes = 32;
	}
	}

	thresh_words = burst_bytes / bytes_per_word;

	/* thresh_words will be between 2 and 8 */
	*threshold = (SSCR1_RxTresh(thresh_words) & SSCR1_RFT)
	\| (SSCR1_TxTresh(16-thresh_words) & SSCR1_TFT);

	return retval;
	}