drivers/spi/omap3_spi.c - u-boot - Git at Google

 /*
  * Copyright (C) 2010 Dirk Behme <dirk.behme@googlemail.com>
  *
  * Driver for McSPI controller on OMAP3. Based on davinci_spi.c
  * Copyright (C) 2009 Texas Instruments Incorporated - http://www.ti.com/
  *
  * Copyright (C) 2007 Atmel Corporation
  *
  * Parts taken from linux/drivers/spi/omap2_mcspi.c
  * Copyright (C) 2005, 2006 Nokia Corporation
  *
  * Modified by Ruslan Araslanov <ruslan.araslanov@vitecmm.com>
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * 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 <common.h>
 #include <spi.h>
 #include <malloc.h>
 #include <asm/io.h>
 #include "omap3_spi.h"

 #define WORD_LEN	8
 #define SPI_WAIT_TIMEOUT 3000000;

 static void spi_reset(struct omap3_spi_slave *ds)
 {
 	unsigned int tmp;

 	writel(OMAP3_MCSPI_SYSCONFIG_SOFTRESET, &ds->regs->sysconfig);
 	do {
 		tmp = readl(&ds->regs->sysstatus);
 	} while (!(tmp & OMAP3_MCSPI_SYSSTATUS_RESETDONE));

 	writel(OMAP3_MCSPI_SYSCONFIG_AUTOIDLE |
 				 OMAP3_MCSPI_SYSCONFIG_ENAWAKEUP |
 				 OMAP3_MCSPI_SYSCONFIG_SMARTIDLE,
 				 &ds->regs->sysconfig);

 	writel(OMAP3_MCSPI_WAKEUPENABLE_WKEN, &ds->regs->wakeupenable);
 }

 void spi_init()
 {
 	/* do nothing */
 }

 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 				  unsigned int max_hz, unsigned int mode)
 {
 	struct omap3_spi_slave	*ds;

 	ds = malloc(sizeof(struct omap3_spi_slave));
 	if (!ds) {
 		printf("SPI error: malloc of SPI structure failed\n");
 		return NULL;
 	}

 	/*
 	 * OMAP3 McSPI (MultiChannel SPI) has 4 busses (modules)
 	 * with different number of chip selects (CS, channels):
 	 * McSPI1 has 4 CS (bus 0, cs 0 - 3)
 	 * McSPI2 has 2 CS (bus 1, cs 0 - 1)
 	 * McSPI3 has 2 CS (bus 2, cs 0 - 1)
 	 * McSPI4 has 1 CS (bus 3, cs 0)
 	 */

 	switch (bus) {
 	case 0:
 		ds->regs = (struct mcspi *)OMAP3_MCSPI1_BASE;
 		break;
 	case 1:
 		ds->regs = (struct mcspi *)OMAP3_MCSPI2_BASE;
 		break;
 	case 2:
 		ds->regs = (struct mcspi *)OMAP3_MCSPI3_BASE;
 		break;
 	case 3:
 		ds->regs = (struct mcspi *)OMAP3_MCSPI4_BASE;
 		break;
 	default:
 		printf("SPI error: unsupported bus %i. \
 			Supported busses 0 - 3\n", bus);
 		return NULL;
 	}
 	ds->slave.bus = bus;

 	if (((bus == 0) && (cs > 3)) ||
 			((bus == 1) && (cs > 1)) ||
 			((bus == 2) && (cs > 1)) ||
 			((bus == 3) && (cs > 0))) {
 		printf("SPI error: unsupported chip select %i \
 			on bus %i\n", cs, bus);
 		return NULL;
 	}
 	ds->slave.cs = cs;

 	if (max_hz > OMAP3_MCSPI_MAX_FREQ) {
 		printf("SPI error: unsupported frequency %i Hz. \
 			Max frequency is 48 Mhz\n", max_hz);
 		return NULL;
 	}
 	ds->freq = max_hz;

 	if (mode > SPI_MODE_3) {
 		printf("SPI error: unsupported SPI mode %i\n", mode);
 		return NULL;
 	}
 	ds->mode = mode;

 	return &ds->slave;
 }

 void spi_free_slave(struct spi_slave *slave)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);

 	free(ds);
 }

 int spi_claim_bus(struct spi_slave *slave)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);
 	unsigned int conf, div = 0;

 	/* McSPI global module configuration */

 	/*
 	 * setup when switching from (reset default) slave mode
 	 * to single-channel master mode
 	 */
 	spi_reset(ds);
 	conf = readl(&ds->regs->modulctrl);
 	conf &= ~(OMAP3_MCSPI_MODULCTRL_STEST | OMAP3_MCSPI_MODULCTRL_MS);
 	conf |= OMAP3_MCSPI_MODULCTRL_SINGLE;
 	writel(conf, &ds->regs->modulctrl);

 	/* McSPI individual channel configuration */

 	/* Calculate clock divisor. Valid range: 0x0 - 0xC ( /1 - /4096 ) */
 	if (ds->freq) {
 		while (div <= 0xC && (OMAP3_MCSPI_MAX_FREQ / (1 << div))
 					 > ds->freq)
 			div++;
 	} else
 		div = 0xC;

 	conf = readl(&ds->regs->channel[ds->slave.cs].chconf);

 	/* standard 4-wire master mode:	SCK, MOSI/out, MISO/in, nCS
 	 * REVISIT: this controller could support SPI_3WIRE mode.
 	 */
 	conf &= ~(OMAP3_MCSPI_CHCONF_IS|OMAP3_MCSPI_CHCONF_DPE1);
 	conf |= OMAP3_MCSPI_CHCONF_DPE0;

 	/* wordlength */
 	conf &= ~OMAP3_MCSPI_CHCONF_WL_MASK;
 	conf |= (WORD_LEN - 1) << 7;

 	/* set chipselect polarity; manage with FORCE */
 	if (!(ds->mode & SPI_CS_HIGH))
 		conf |= OMAP3_MCSPI_CHCONF_EPOL; /* active-low; normal */
 	else
 		conf &= ~OMAP3_MCSPI_CHCONF_EPOL;

 	/* set clock divisor */
 	conf &= ~OMAP3_MCSPI_CHCONF_CLKD_MASK;
 	conf |= div << 2;

 	/* set SPI mode 0..3 */
 	if (ds->mode & SPI_CPOL)
 		conf |= OMAP3_MCSPI_CHCONF_POL;
 	else
 		conf &= ~OMAP3_MCSPI_CHCONF_POL;
 	if (ds->mode & SPI_CPHA)
 		conf |= OMAP3_MCSPI_CHCONF_PHA;
 	else
 		conf &= ~OMAP3_MCSPI_CHCONF_PHA;

 	/* Transmit & receive mode */
 	conf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;

 	writel(conf, &ds->regs->channel[ds->slave.cs].chconf);

 	return 0;
 }

 void spi_release_bus(struct spi_slave *slave)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);

 	/* Reset the SPI hardware */
 	spi_reset(ds);
 }

 int omap3_spi_write(struct spi_slave *slave, unsigned int len, const u8 *txp,
 		    unsigned long flags)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);
 	int i;
 	int timeout = SPI_WAIT_TIMEOUT;
 	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

 	if (flags & SPI_XFER_BEGIN)
 		writel(OMAP3_MCSPI_CHCTRL_EN,
 		       &ds->regs->channel[ds->slave.cs].chctrl);

 	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 	chconf |= OMAP3_MCSPI_CHCONF_TRM_TX_ONLY;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
 	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

 	for (i = 0; i < len; i++) {
 		/* wait till TX register is empty (TXS == 1) */
 		while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
 			 OMAP3_MCSPI_CHSTAT_TXS)) {
 			if (--timeout <= 0) {
 				printf("SPI TXS timed out, status=0x%08x\n",
 				       readl(&ds->regs->channel[ds->slave.cs].chstat));
 				return -1;
 			}
 		}
 		/* Write the data */
 		writel(txp[i], &ds->regs->channel[ds->slave.cs].tx);
 	}

 	if (flags & SPI_XFER_END) {
 		/* wait to finish of transfer */
 		while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
 			 OMAP3_MCSPI_CHSTAT_EOT));

 		chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
 		writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

 		writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
 	}
 	return 0;
 }

 int omap3_spi_read(struct spi_slave *slave, unsigned int len, u8 *rxp,
 		   unsigned long flags)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);
 	int i;
 	int timeout = SPI_WAIT_TIMEOUT;
 	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

 	if (flags & SPI_XFER_BEGIN)
 		writel(OMAP3_MCSPI_CHCTRL_EN,
 		       &ds->regs->channel[ds->slave.cs].chctrl);

 	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 	chconf |= OMAP3_MCSPI_CHCONF_TRM_RX_ONLY;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
 	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

 	writel(0, &ds->regs->channel[ds->slave.cs].tx);

 	for (i = 0; i < len; i++) {
 		/* Wait till RX register contains data (RXS == 1) */
 		while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
 			 OMAP3_MCSPI_CHSTAT_RXS)) {
 			if (--timeout <= 0) {
 				printf("SPI RXS timed out, status=0x%08x\n",
 				       readl(&ds->regs->channel[ds->slave.cs].chstat));
 				return -1;
 			}
 		}
 		/* Read the data */
 		rxp[i] = readl(&ds->regs->channel[ds->slave.cs].rx);
 	}

 	if (flags & SPI_XFER_END) {
 		chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
 		writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

 		writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
 	}

 	return 0;
 }

 int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 	     const void *dout, void *din, unsigned long flags)
 {
 	struct omap3_spi_slave *ds = to_omap3_spi(slave);
 	unsigned int	len;
 	const u8	*txp = dout;
 	u8		*rxp = din;
 	int ret = -1;

 	if (bitlen % 8)
 		return -1;

 	len = bitlen / 8;

 	if (bitlen == 0) {	 /* only change CS */
 		int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

 		if (flags & SPI_XFER_BEGIN) {
 			writel(OMAP3_MCSPI_CHCTRL_EN,
 			       &ds->regs->channel[ds->slave.cs].chctrl);
 			chconf |= OMAP3_MCSPI_CHCONF_FORCE;
 			writel(chconf,
 			       &ds->regs->channel[ds->slave.cs].chconf);
 		}
 		if (flags & SPI_XFER_END) {
 			chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
 			writel(chconf,
 			       &ds->regs->channel[ds->slave.cs].chconf);
 			writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
 		}
 		ret = 0;
 	} else {
 		if (dout != NULL)
 			ret = omap3_spi_write(slave, len, txp, flags);

 		if (din != NULL)
 			ret = omap3_spi_read(slave, len, rxp, flags);
 	}
 	return ret;
 }

 int spi_cs_is_valid(unsigned int bus, unsigned int cs)
 {
 	return 1;
 }

 void spi_cs_activate(struct spi_slave *slave)
 {
 }

 void spi_cs_deactivate(struct spi_slave *slave)
 {
 }
	/*
	* Copyright (C) 2010 Dirk Behme <dirk.behme@googlemail.com>
	*
	* Driver for McSPI controller on OMAP3. Based on davinci_spi.c
	* Copyright (C) 2009 Texas Instruments Incorporated - http://www.ti.com/
	*
	* Copyright (C) 2007 Atmel Corporation
	*
	* Parts taken from linux/drivers/spi/omap2_mcspi.c
	* Copyright (C) 2005, 2006 Nokia Corporation
	*
	* Modified by Ruslan Araslanov <ruslan.araslanov@vitecmm.com>
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* 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 <common.h>
	#include <spi.h>
	#include <malloc.h>
	#include <asm/io.h>
	#include "omap3_spi.h"

	#define WORD_LEN 8
	#define SPI_WAIT_TIMEOUT 3000000;

	static void spi_reset(struct omap3_spi_slave *ds)
	{
	unsigned int tmp;

	writel(OMAP3_MCSPI_SYSCONFIG_SOFTRESET, &ds->regs->sysconfig);
	do {
	tmp = readl(&ds->regs->sysstatus);
	} while (!(tmp & OMAP3_MCSPI_SYSSTATUS_RESETDONE));

	writel(OMAP3_MCSPI_SYSCONFIG_AUTOIDLE \|
	OMAP3_MCSPI_SYSCONFIG_ENAWAKEUP \|
	OMAP3_MCSPI_SYSCONFIG_SMARTIDLE,
	&ds->regs->sysconfig);

	writel(OMAP3_MCSPI_WAKEUPENABLE_WKEN, &ds->regs->wakeupenable);
	}

	void spi_init()
	{
	/* do nothing */
	}

	struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	struct omap3_spi_slave *ds;

	ds = malloc(sizeof(struct omap3_spi_slave));
	if (!ds) {
	printf("SPI error: malloc of SPI structure failed\n");
	return NULL;
	}

	/*
	* OMAP3 McSPI (MultiChannel SPI) has 4 busses (modules)
	* with different number of chip selects (CS, channels):
	* McSPI1 has 4 CS (bus 0, cs 0 - 3)
	* McSPI2 has 2 CS (bus 1, cs 0 - 1)
	* McSPI3 has 2 CS (bus 2, cs 0 - 1)
	* McSPI4 has 1 CS (bus 3, cs 0)
	*/

	switch (bus) {
	case 0:
	ds->regs = (struct mcspi *)OMAP3_MCSPI1_BASE;
	break;
	case 1:
	ds->regs = (struct mcspi *)OMAP3_MCSPI2_BASE;
	break;
	case 2:
	ds->regs = (struct mcspi *)OMAP3_MCSPI3_BASE;
	break;
	case 3:
	ds->regs = (struct mcspi *)OMAP3_MCSPI4_BASE;
	break;
	default:
	printf("SPI error: unsupported bus %i. \
	Supported busses 0 - 3\n", bus);
	return NULL;
	}
	ds->slave.bus = bus;

	if (((bus == 0) && (cs > 3)) \|\|
	((bus == 1) && (cs > 1)) \|\|
	((bus == 2) && (cs > 1)) \|\|
	((bus == 3) && (cs > 0))) {
	printf("SPI error: unsupported chip select %i \
	on bus %i\n", cs, bus);
	return NULL;
	}
	ds->slave.cs = cs;

	if (max_hz > OMAP3_MCSPI_MAX_FREQ) {
	printf("SPI error: unsupported frequency %i Hz. \
	Max frequency is 48 Mhz\n", max_hz);
	return NULL;
	}
	ds->freq = max_hz;

	if (mode > SPI_MODE_3) {
	printf("SPI error: unsupported SPI mode %i\n", mode);
	return NULL;
	}
	ds->mode = mode;

	return &ds->slave;
	}

	void spi_free_slave(struct spi_slave *slave)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);

	free(ds);
	}

	int spi_claim_bus(struct spi_slave *slave)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);
	unsigned int conf, div = 0;

	/* McSPI global module configuration */

	/*
	* setup when switching from (reset default) slave mode
	* to single-channel master mode
	*/
	spi_reset(ds);
	conf = readl(&ds->regs->modulctrl);
	conf &= ~(OMAP3_MCSPI_MODULCTRL_STEST \| OMAP3_MCSPI_MODULCTRL_MS);
	conf \|= OMAP3_MCSPI_MODULCTRL_SINGLE;
	writel(conf, &ds->regs->modulctrl);

	/* McSPI individual channel configuration */

	/* Calculate clock divisor. Valid range: 0x0 - 0xC ( /1 - /4096 ) */
	if (ds->freq) {
	while (div <= 0xC && (OMAP3_MCSPI_MAX_FREQ / (1 << div))
	> ds->freq)
	div++;
	} else
	div = 0xC;

	conf = readl(&ds->regs->channel[ds->slave.cs].chconf);

	/* standard 4-wire master mode: SCK, MOSI/out, MISO/in, nCS
	* REVISIT: this controller could support SPI_3WIRE mode.
	*/
	conf &= ~(OMAP3_MCSPI_CHCONF_IS\|OMAP3_MCSPI_CHCONF_DPE1);
	conf \|= OMAP3_MCSPI_CHCONF_DPE0;

	/* wordlength */
	conf &= ~OMAP3_MCSPI_CHCONF_WL_MASK;
	conf \|= (WORD_LEN - 1) << 7;

	/* set chipselect polarity; manage with FORCE */
	if (!(ds->mode & SPI_CS_HIGH))
	conf \|= OMAP3_MCSPI_CHCONF_EPOL; /* active-low; normal */
	else
	conf &= ~OMAP3_MCSPI_CHCONF_EPOL;

	/* set clock divisor */
	conf &= ~OMAP3_MCSPI_CHCONF_CLKD_MASK;
	conf \|= div << 2;

	/* set SPI mode 0..3 */
	if (ds->mode & SPI_CPOL)
	conf \|= OMAP3_MCSPI_CHCONF_POL;
	else
	conf &= ~OMAP3_MCSPI_CHCONF_POL;
	if (ds->mode & SPI_CPHA)
	conf \|= OMAP3_MCSPI_CHCONF_PHA;
	else
	conf &= ~OMAP3_MCSPI_CHCONF_PHA;

	/* Transmit & receive mode */
	conf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;

	writel(conf, &ds->regs->channel[ds->slave.cs].chconf);

	return 0;
	}

	void spi_release_bus(struct spi_slave *slave)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);

	/* Reset the SPI hardware */
	spi_reset(ds);
	}

	int omap3_spi_write(struct spi_slave slave, unsigned int len, const u8 txp,
	unsigned long flags)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);
	int i;
	int timeout = SPI_WAIT_TIMEOUT;
	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

	if (flags & SPI_XFER_BEGIN)
	writel(OMAP3_MCSPI_CHCTRL_EN,
	&ds->regs->channel[ds->slave.cs].chctrl);

	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
	chconf \|= OMAP3_MCSPI_CHCONF_TRM_TX_ONLY;
	chconf \|= OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

	for (i = 0; i < len; i++) {
	/* wait till TX register is empty (TXS == 1) */
	while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
	OMAP3_MCSPI_CHSTAT_TXS)) {
	if (--timeout <= 0) {
	printf("SPI TXS timed out, status=0x%08x\n",
	readl(&ds->regs->channel[ds->slave.cs].chstat));
	return -1;
	}
	}
	/* Write the data */
	writel(txp[i], &ds->regs->channel[ds->slave.cs].tx);
	}

	if (flags & SPI_XFER_END) {
	/* wait to finish of transfer */
	while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
	OMAP3_MCSPI_CHSTAT_EOT));

	chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

	writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
	}
	return 0;
	}

	int omap3_spi_read(struct spi_slave slave, unsigned int len, u8 rxp,
	unsigned long flags)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);
	int i;
	int timeout = SPI_WAIT_TIMEOUT;
	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

	if (flags & SPI_XFER_BEGIN)
	writel(OMAP3_MCSPI_CHCTRL_EN,
	&ds->regs->channel[ds->slave.cs].chctrl);

	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
	chconf \|= OMAP3_MCSPI_CHCONF_TRM_RX_ONLY;
	chconf \|= OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

	writel(0, &ds->regs->channel[ds->slave.cs].tx);

	for (i = 0; i < len; i++) {
	/* Wait till RX register contains data (RXS == 1) */
	while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
	OMAP3_MCSPI_CHSTAT_RXS)) {
	if (--timeout <= 0) {
	printf("SPI RXS timed out, status=0x%08x\n",
	readl(&ds->regs->channel[ds->slave.cs].chstat));
	return -1;
	}
	}
	/* Read the data */
	rxp[i] = readl(&ds->regs->channel[ds->slave.cs].rx);
	}

	if (flags & SPI_XFER_END) {
	chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);

	writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
	}

	return 0;
	}

	int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
	const void dout, void din, unsigned long flags)
	{
	struct omap3_spi_slave *ds = to_omap3_spi(slave);
	unsigned int len;
	const u8 *txp = dout;
	u8 *rxp = din;
	int ret = -1;

	if (bitlen % 8)
	return -1;

	len = bitlen / 8;

	if (bitlen == 0) { /* only change CS */
	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);

	if (flags & SPI_XFER_BEGIN) {
	writel(OMAP3_MCSPI_CHCTRL_EN,
	&ds->regs->channel[ds->slave.cs].chctrl);
	chconf \|= OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf,
	&ds->regs->channel[ds->slave.cs].chconf);
	}
	if (flags & SPI_XFER_END) {
	chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
	writel(chconf,
	&ds->regs->channel[ds->slave.cs].chconf);
	writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
	}
	ret = 0;
	} else {
	if (dout != NULL)
	ret = omap3_spi_write(slave, len, txp, flags);

	if (din != NULL)
	ret = omap3_spi_read(slave, len, rxp, flags);
	}
	return ret;
	}

	int spi_cs_is_valid(unsigned int bus, unsigned int cs)
	{
	return 1;
	}

	void spi_cs_activate(struct spi_slave *slave)
	{
	}

	void spi_cs_deactivate(struct spi_slave *slave)
	{
	}