drivers/spi/mxc_spi.c - github/trini/u-boot - Gitiles

 /*
  * Copyright (C) 2008, Guennadi Liakhovetski <lg@denx.de>
  *
  * 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 <malloc.h>
 #include <spi.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <asm/gpio.h>
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/clock.h>

 #ifdef CONFIG_MX27
 /* i.MX27 has a completely wrong register layout and register definitions in the
  * datasheet, the correct one is in the Freescale's Linux driver */

 #error "i.MX27 CSPI not supported due to drastic differences in register definitions" \
 "See linux mxc_spi driver from Freescale for details."
 #endif

 static unsigned long spi_bases[] = {
 	MXC_SPI_BASE_ADDRESSES
 };

 #define OUT	MXC_GPIO_DIRECTION_OUT

 #define reg_read readl
 #define reg_write(a, v) writel(v, a)

 struct mxc_spi_slave {
 	struct spi_slave slave;
 	unsigned long	base;
 	u32		ctrl_reg;
 #if defined(MXC_ECSPI)
 	u32		cfg_reg;
 #endif
 	int		gpio;
 	int		ss_pol;
 };

 static inline struct mxc_spi_slave *to_mxc_spi_slave(struct spi_slave *slave)
 {
 	return container_of(slave, struct mxc_spi_slave, slave);
 }

 void spi_cs_activate(struct spi_slave *slave)
 {
 	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
 	if (mxcs->gpio > 0)
 		gpio_set_value(mxcs->gpio, mxcs->ss_pol);
 }

 void spi_cs_deactivate(struct spi_slave *slave)
 {
 	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
 	if (mxcs->gpio > 0)
 		gpio_set_value(mxcs->gpio,
 			      !(mxcs->ss_pol));
 }

 u32 get_cspi_div(u32 div)
 {
 	int i;

 	for (i = 0; i < 8; i++) {
 		if (div <= (4 << i))
 			return i;
 	}
 	return i;
 }

 #ifdef MXC_CSPI
 static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 		unsigned int max_hz, unsigned int mode)
 {
 	unsigned int ctrl_reg;
 	u32 clk_src;
 	u32 div;

 	clk_src = mxc_get_clock(MXC_CSPI_CLK);

 	div = DIV_ROUND_UP(clk_src, max_hz);
 	div = get_cspi_div(div);

 	debug("clk %d Hz, div %d, real clk %d Hz\n",
 		max_hz, div, clk_src / (4 << div));

 	ctrl_reg = MXC_CSPICTRL_CHIPSELECT(cs) |
 		MXC_CSPICTRL_BITCOUNT(MXC_CSPICTRL_MAXBITS) |
 		MXC_CSPICTRL_DATARATE(div) |
 		MXC_CSPICTRL_EN |
 #ifdef CONFIG_MX35
 		MXC_CSPICTRL_SSCTL |
 #endif
 		MXC_CSPICTRL_MODE;

 	if (mode & SPI_CPHA)
 		ctrl_reg |= MXC_CSPICTRL_PHA;
 	if (mode & SPI_CPOL)
 		ctrl_reg |= MXC_CSPICTRL_POL;
 	if (mode & SPI_CS_HIGH)
 		ctrl_reg |= MXC_CSPICTRL_SSPOL;
 	mxcs->ctrl_reg = ctrl_reg;

 	return 0;
 }
 #endif

 #ifdef MXC_ECSPI
 static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 		unsigned int max_hz, unsigned int mode)
 {
 	u32 clk_src = mxc_get_clock(MXC_CSPI_CLK);
 	s32 pre_div = 0, post_div = 0, i, reg_ctrl, reg_config;
 	u32 ss_pol = 0, sclkpol = 0, sclkpha = 0;
 	struct cspi_regs *regs = (struct cspi_regs *)mxcs->base;

 	if (max_hz == 0) {
 		printf("Error: desired clock is 0\n");
 		return -1;
 	}

 	/*
 	 * Reset SPI and set all CSs to master mode, if toggling
 	 * between slave and master mode we might see a glitch
 	 * on the clock line
 	 */
 	reg_ctrl = MXC_CSPICTRL_MODE_MASK;
 	reg_write(&regs->ctrl, reg_ctrl);
 	reg_ctrl |=  MXC_CSPICTRL_EN;
 	reg_write(&regs->ctrl, reg_ctrl);

 	/*
 	 * The following computation is taken directly from Freescale's code.
 	 */
 	if (clk_src > max_hz) {
 		pre_div = DIV_ROUND_UP(clk_src, max_hz);
 		if (pre_div > 16) {
 			post_div = pre_div / 16;
 			pre_div = 15;
 		}
 		if (post_div != 0) {
 			for (i = 0; i < 16; i++) {
 				if ((1 << i) >= post_div)
 					break;
 			}
 			if (i == 16) {
 				printf("Error: no divider for the freq: %d\n",
 					max_hz);
 				return -1;
 			}
 			post_div = i;
 		}
 	}

 	debug("pre_div = %d, post_div=%d\n", pre_div, post_div);
 	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_SELCHAN(3)) |
 		MXC_CSPICTRL_SELCHAN(cs);
 	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_PREDIV(0x0F)) |
 		MXC_CSPICTRL_PREDIV(pre_div);
 	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_POSTDIV(0x0F)) |
 		MXC_CSPICTRL_POSTDIV(post_div);

 	/* We need to disable SPI before changing registers */
 	reg_ctrl &= ~MXC_CSPICTRL_EN;

 	if (mode & SPI_CS_HIGH)
 		ss_pol = 1;

 	if (mode & SPI_CPOL)
 		sclkpol = 1;

 	if (mode & SPI_CPHA)
 		sclkpha = 1;

 	reg_config = reg_read(&regs->cfg);

 	/*
 	 * Configuration register setup
 	 * The MX51 supports different setup for each SS
 	 */
 	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_SSPOL))) |
 		(ss_pol << (cs + MXC_CSPICON_SSPOL));
 	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_POL))) |
 		(sclkpol << (cs + MXC_CSPICON_POL));
 	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_PHA))) |
 		(sclkpha << (cs + MXC_CSPICON_PHA));

 	debug("reg_ctrl = 0x%x\n", reg_ctrl);
 	reg_write(&regs->ctrl, reg_ctrl);
 	debug("reg_config = 0x%x\n", reg_config);
 	reg_write(&regs->cfg, reg_config);

 	/* save config register and control register */
 	mxcs->ctrl_reg = reg_ctrl;
 	mxcs->cfg_reg = reg_config;

 	/* clear interrupt reg */
 	reg_write(&regs->intr, 0);
 	reg_write(&regs->stat, MXC_CSPICTRL_TC | MXC_CSPICTRL_RXOVF);

 	return 0;
 }
 #endif

 int spi_xchg_single(struct spi_slave *slave, unsigned int bitlen,
 	const u8 *dout, u8 *din, unsigned long flags)
 {
 	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
 	int nbytes = (bitlen + 7) / 8;
 	u32 data, cnt, i;
 	struct cspi_regs *regs = (struct cspi_regs *)mxcs->base;

 	debug("%s: bitlen %d dout 0x%x din 0x%x\n",
 		__func__, bitlen, (u32)dout, (u32)din);

 	mxcs->ctrl_reg = (mxcs->ctrl_reg &
 		~MXC_CSPICTRL_BITCOUNT(MXC_CSPICTRL_MAXBITS)) |
 		MXC_CSPICTRL_BITCOUNT(bitlen - 1);

 	reg_write(&regs->ctrl, mxcs->ctrl_reg | MXC_CSPICTRL_EN);
 #ifdef MXC_ECSPI
 	reg_write(&regs->cfg, mxcs->cfg_reg);
 #endif

 	/* Clear interrupt register */
 	reg_write(&regs->stat, MXC_CSPICTRL_TC | MXC_CSPICTRL_RXOVF);

 	/*
 	 * The SPI controller works only with words,
 	 * check if less than a word is sent.
 	 * Access to the FIFO is only 32 bit
 	 */
 	if (bitlen % 32) {
 		data = 0;
 		cnt = (bitlen % 32) / 8;
 		if (dout) {
 			for (i = 0; i < cnt; i++) {
 				data = (data << 8) | (*dout++ & 0xFF);
 			}
 		}
 		debug("Sending SPI 0x%x\n", data);

 		reg_write(&regs->txdata, data);
 		nbytes -= cnt;
 	}

 	data = 0;

 	while (nbytes > 0) {
 		data = 0;
 		if (dout) {
 			/* Buffer is not 32-bit aligned */
 			if ((unsigned long)dout & 0x03) {
 				data = 0;
 				for (i = 0; i < 4; i++)
 					data = (data << 8) | (*dout++ & 0xFF);
 			} else {
 				data = *(u32 *)dout;
 				data = cpu_to_be32(data);
 			}
 			dout += 4;
 		}
 		debug("Sending SPI 0x%x\n", data);
 		reg_write(&regs->txdata, data);
 		nbytes -= 4;
 	}

 	/* FIFO is written, now starts the transfer setting the XCH bit */
 	reg_write(&regs->ctrl, mxcs->ctrl_reg |
 		MXC_CSPICTRL_EN | MXC_CSPICTRL_XCH);

 	/* Wait until the TC (Transfer completed) bit is set */
 	while ((reg_read(&regs->stat) & MXC_CSPICTRL_TC) == 0)
 		;

 	/* Transfer completed, clear any pending request */
 	reg_write(&regs->stat, MXC_CSPICTRL_TC | MXC_CSPICTRL_RXOVF);

 	nbytes = (bitlen + 7) / 8;

 	cnt = nbytes % 32;

 	if (bitlen % 32) {
 		data = reg_read(&regs->rxdata);
 		cnt = (bitlen % 32) / 8;
 		data = cpu_to_be32(data) >> ((sizeof(data) - cnt) * 8);
 		debug("SPI Rx unaligned: 0x%x\n", data);
 		if (din) {
 			memcpy(din, &data, cnt);
 			din += cnt;
 		}
 		nbytes -= cnt;
 	}

 	while (nbytes > 0) {
 		u32 tmp;
 		tmp = reg_read(&regs->rxdata);
 		data = cpu_to_be32(tmp);
 		debug("SPI Rx: 0x%x 0x%x\n", tmp, data);
 		cnt = min(nbytes, sizeof(data));
 		if (din) {
 			memcpy(din, &data, cnt);
 			din += cnt;
 		}
 		nbytes -= cnt;
 	}

 	return 0;

 }

 int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 		void *din, unsigned long flags)
 {
 	int n_bytes = (bitlen + 7) / 8;
 	int n_bits;
 	int ret;
 	u32 blk_size;
 	u8 *p_outbuf = (u8 *)dout;
 	u8 *p_inbuf = (u8 *)din;

 	if (!slave)
 		return -1;

 	if (flags & SPI_XFER_BEGIN)
 		spi_cs_activate(slave);

 	while (n_bytes > 0) {
 		if (n_bytes < MAX_SPI_BYTES)
 			blk_size = n_bytes;
 		else
 			blk_size = MAX_SPI_BYTES;

 		n_bits = blk_size * 8;

 		ret = spi_xchg_single(slave, n_bits, p_outbuf, p_inbuf, 0);

 		if (ret)
 			return ret;
 		if (dout)
 			p_outbuf += blk_size;
 		if (din)
 			p_inbuf += blk_size;
 		n_bytes -= blk_size;
 	}

 	if (flags & SPI_XFER_END) {
 		spi_cs_deactivate(slave);
 	}

 	return 0;
 }

 void spi_init(void)
 {
 }

 static int decode_cs(struct mxc_spi_slave *mxcs, unsigned int cs)
 {
 	int ret;

 	/*
 	 * Some SPI devices require active chip-select over multiple
 	 * transactions, we achieve this using a GPIO. Still, the SPI
 	 * controller has to be configured to use one of its own chipselects.
 	 * To use this feature you have to call spi_setup_slave() with
 	 * cs = internal_cs | (gpio << 8), and you have to use some unused
 	 * on this SPI controller cs between 0 and 3.
 	 */
 	if (cs > 3) {
 		mxcs->gpio = cs >> 8;
 		cs &= 3;
 		ret = gpio_direction_output(mxcs->gpio, !(mxcs->ss_pol));
 		if (ret) {
 			printf("mxc_spi: cannot setup gpio %d\n", mxcs->gpio);
 			return -EINVAL;
 		}
 	} else {
 		mxcs->gpio = -1;
 	}

 	return cs;
 }

 struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
 			unsigned int max_hz, unsigned int mode)
 {
 	struct mxc_spi_slave *mxcs;
 	int ret;

 	if (bus >= ARRAY_SIZE(spi_bases))
 		return NULL;

 	mxcs = spi_alloc_slave(struct mxc_spi_slave, bus, cs);
 	if (!mxcs) {
 		puts("mxc_spi: SPI Slave not allocated !\n");
 		return NULL;
 	}

 	mxcs->ss_pol = (mode & SPI_CS_HIGH) ? 1 : 0;

 	ret = decode_cs(mxcs, cs);
 	if (ret < 0) {
 		free(mxcs);
 		return NULL;
 	}

 	cs = ret;

 	mxcs->base = spi_bases[bus];

 	ret = spi_cfg_mxc(mxcs, cs, max_hz, mode);
 	if (ret) {
 		printf("mxc_spi: cannot setup SPI controller\n");
 		free(mxcs);
 		return NULL;
 	}
 	return &mxcs->slave;
 }

 void spi_free_slave(struct spi_slave *slave)
 {
 	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);

 	free(mxcs);
 }

 int spi_claim_bus(struct spi_slave *slave)
 {
 	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
 	struct cspi_regs *regs = (struct cspi_regs *)mxcs->base;

 	reg_write(&regs->rxdata, 1);
 	udelay(1);
 	reg_write(&regs->ctrl, mxcs->ctrl_reg);
 	reg_write(&regs->period, MXC_CSPIPERIOD_32KHZ);
 	reg_write(&regs->intr, 0);

 	return 0;
 }

 void spi_release_bus(struct spi_slave *slave)
 {
 	/* TODO: Shut the controller down */
 }
	/*
	* Copyright (C) 2008, Guennadi Liakhovetski <lg@denx.de>
	*
	* 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 <malloc.h>
	#include <spi.h>
	#include <asm/errno.h>
	#include <asm/io.h>
	#include <asm/gpio.h>
	#include <asm/arch/imx-regs.h>
	#include <asm/arch/clock.h>

	#ifdef CONFIG_MX27
	/* i.MX27 has a completely wrong register layout and register definitions in the
	* datasheet, the correct one is in the Freescale's Linux driver */

	#error "i.MX27 CSPI not supported due to drastic differences in register definitions" \
	"See linux mxc_spi driver from Freescale for details."
	#endif

	static unsigned long spi_bases[] = {
	MXC_SPI_BASE_ADDRESSES
	};

	#define OUT MXC_GPIO_DIRECTION_OUT

	#define reg_read readl
	#define reg_write(a, v) writel(v, a)

	struct mxc_spi_slave {
	struct spi_slave slave;
	unsigned long base;
	u32 ctrl_reg;
	#if defined(MXC_ECSPI)
	u32 cfg_reg;
	#endif
	int gpio;
	int ss_pol;
	};

	static inline struct mxc_spi_slave to_mxc_spi_slave(struct spi_slave slave)
	{
	return container_of(slave, struct mxc_spi_slave, slave);
	}

	void spi_cs_activate(struct spi_slave *slave)
	{
	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
	if (mxcs->gpio > 0)
	gpio_set_value(mxcs->gpio, mxcs->ss_pol);
	}

	void spi_cs_deactivate(struct spi_slave *slave)
	{
	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
	if (mxcs->gpio > 0)
	gpio_set_value(mxcs->gpio,
	!(mxcs->ss_pol));
	}

	u32 get_cspi_div(u32 div)
	{
	int i;

	for (i = 0; i < 8; i++) {
	if (div <= (4 << i))
	return i;
	}
	return i;
	}

	#ifdef MXC_CSPI
	static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	unsigned int ctrl_reg;
	u32 clk_src;
	u32 div;

	clk_src = mxc_get_clock(MXC_CSPI_CLK);

	div = DIV_ROUND_UP(clk_src, max_hz);
	div = get_cspi_div(div);

	debug("clk %d Hz, div %d, real clk %d Hz\n",
	max_hz, div, clk_src / (4 << div));

	ctrl_reg = MXC_CSPICTRL_CHIPSELECT(cs) \|
	MXC_CSPICTRL_BITCOUNT(MXC_CSPICTRL_MAXBITS) \|
	MXC_CSPICTRL_DATARATE(div) \|
	MXC_CSPICTRL_EN \|
	#ifdef CONFIG_MX35
	MXC_CSPICTRL_SSCTL \|
	#endif
	MXC_CSPICTRL_MODE;

	if (mode & SPI_CPHA)
	ctrl_reg \|= MXC_CSPICTRL_PHA;
	if (mode & SPI_CPOL)
	ctrl_reg \|= MXC_CSPICTRL_POL;
	if (mode & SPI_CS_HIGH)
	ctrl_reg \|= MXC_CSPICTRL_SSPOL;
	mxcs->ctrl_reg = ctrl_reg;

	return 0;
	}
	#endif

	#ifdef MXC_ECSPI
	static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	u32 clk_src = mxc_get_clock(MXC_CSPI_CLK);
	s32 pre_div = 0, post_div = 0, i, reg_ctrl, reg_config;
	u32 ss_pol = 0, sclkpol = 0, sclkpha = 0;
	struct cspi_regs regs = (struct cspi_regs )mxcs->base;

	if (max_hz == 0) {
	printf("Error: desired clock is 0\n");
	return -1;
	}

	/*
	* Reset SPI and set all CSs to master mode, if toggling
	* between slave and master mode we might see a glitch
	* on the clock line
	*/
	reg_ctrl = MXC_CSPICTRL_MODE_MASK;
	reg_write(&regs->ctrl, reg_ctrl);
	reg_ctrl \|= MXC_CSPICTRL_EN;
	reg_write(&regs->ctrl, reg_ctrl);

	/*
	* The following computation is taken directly from Freescale's code.
	*/
	if (clk_src > max_hz) {
	pre_div = DIV_ROUND_UP(clk_src, max_hz);
	if (pre_div > 16) {
	post_div = pre_div / 16;
	pre_div = 15;
	}
	if (post_div != 0) {
	for (i = 0; i < 16; i++) {
	if ((1 << i) >= post_div)
	break;
	}
	if (i == 16) {
	printf("Error: no divider for the freq: %d\n",
	max_hz);
	return -1;
	}
	post_div = i;
	}
	}

	debug("pre_div = %d, post_div=%d\n", pre_div, post_div);
	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_SELCHAN(3)) \|
	MXC_CSPICTRL_SELCHAN(cs);
	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_PREDIV(0x0F)) \|
	MXC_CSPICTRL_PREDIV(pre_div);
	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_POSTDIV(0x0F)) \|
	MXC_CSPICTRL_POSTDIV(post_div);

	/* We need to disable SPI before changing registers */
	reg_ctrl &= ~MXC_CSPICTRL_EN;

	if (mode & SPI_CS_HIGH)
	ss_pol = 1;

	if (mode & SPI_CPOL)
	sclkpol = 1;

	if (mode & SPI_CPHA)
	sclkpha = 1;

	reg_config = reg_read(&regs->cfg);

	/*
	* Configuration register setup
	* The MX51 supports different setup for each SS
	*/
	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_SSPOL))) \|
	(ss_pol << (cs + MXC_CSPICON_SSPOL));
	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_POL))) \|
	(sclkpol << (cs + MXC_CSPICON_POL));
	reg_config = (reg_config & ~(1 << (cs + MXC_CSPICON_PHA))) \|
	(sclkpha << (cs + MXC_CSPICON_PHA));

	debug("reg_ctrl = 0x%x\n", reg_ctrl);
	reg_write(&regs->ctrl, reg_ctrl);
	debug("reg_config = 0x%x\n", reg_config);
	reg_write(&regs->cfg, reg_config);

	/* save config register and control register */
	mxcs->ctrl_reg = reg_ctrl;
	mxcs->cfg_reg = reg_config;

	/* clear interrupt reg */
	reg_write(&regs->intr, 0);
	reg_write(&regs->stat, MXC_CSPICTRL_TC \| MXC_CSPICTRL_RXOVF);

	return 0;
	}
	#endif

	int spi_xchg_single(struct spi_slave *slave, unsigned int bitlen,
	const u8 dout, u8 din, unsigned long flags)
	{
	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
	int nbytes = (bitlen + 7) / 8;
	u32 data, cnt, i;
	struct cspi_regs regs = (struct cspi_regs )mxcs->base;

	debug("%s: bitlen %d dout 0x%x din 0x%x\n",
	__func__, bitlen, (u32)dout, (u32)din);

	mxcs->ctrl_reg = (mxcs->ctrl_reg &
	~MXC_CSPICTRL_BITCOUNT(MXC_CSPICTRL_MAXBITS)) \|
	MXC_CSPICTRL_BITCOUNT(bitlen - 1);

	reg_write(&regs->ctrl, mxcs->ctrl_reg \| MXC_CSPICTRL_EN);
	#ifdef MXC_ECSPI
	reg_write(&regs->cfg, mxcs->cfg_reg);
	#endif

	/* Clear interrupt register */
	reg_write(&regs->stat, MXC_CSPICTRL_TC \| MXC_CSPICTRL_RXOVF);

	/*
	* The SPI controller works only with words,
	* check if less than a word is sent.
	* Access to the FIFO is only 32 bit
	*/
	if (bitlen % 32) {
	data = 0;
	cnt = (bitlen % 32) / 8;
	if (dout) {
	for (i = 0; i < cnt; i++) {
	data = (data << 8) \| (*dout++ & 0xFF);
	}
	}
	debug("Sending SPI 0x%x\n", data);

	reg_write(&regs->txdata, data);
	nbytes -= cnt;
	}

	data = 0;

	while (nbytes > 0) {
	data = 0;
	if (dout) {
	/* Buffer is not 32-bit aligned */
	if ((unsigned long)dout & 0x03) {
	data = 0;
	for (i = 0; i < 4; i++)
	data = (data << 8) \| (*dout++ & 0xFF);
	} else {
	data = (u32 )dout;
	data = cpu_to_be32(data);
	}
	dout += 4;
	}
	debug("Sending SPI 0x%x\n", data);
	reg_write(&regs->txdata, data);
	nbytes -= 4;
	}

	/* FIFO is written, now starts the transfer setting the XCH bit */
	reg_write(&regs->ctrl, mxcs->ctrl_reg \|
	MXC_CSPICTRL_EN \| MXC_CSPICTRL_XCH);

	/* Wait until the TC (Transfer completed) bit is set */
	while ((reg_read(&regs->stat) & MXC_CSPICTRL_TC) == 0)
	;

	/* Transfer completed, clear any pending request */
	reg_write(&regs->stat, MXC_CSPICTRL_TC \| MXC_CSPICTRL_RXOVF);

	nbytes = (bitlen + 7) / 8;

	cnt = nbytes % 32;

	if (bitlen % 32) {
	data = reg_read(&regs->rxdata);
	cnt = (bitlen % 32) / 8;
	data = cpu_to_be32(data) >> ((sizeof(data) - cnt) * 8);
	debug("SPI Rx unaligned: 0x%x\n", data);
	if (din) {
	memcpy(din, &data, cnt);
	din += cnt;
	}
	nbytes -= cnt;
	}

	while (nbytes > 0) {
	u32 tmp;
	tmp = reg_read(&regs->rxdata);
	data = cpu_to_be32(tmp);
	debug("SPI Rx: 0x%x 0x%x\n", tmp, data);
	cnt = min(nbytes, sizeof(data));
	if (din) {
	memcpy(din, &data, cnt);
	din += cnt;
	}
	nbytes -= cnt;
	}

	return 0;

	}

	int spi_xfer(struct spi_slave slave, unsigned int bitlen, const void dout,
	void *din, unsigned long flags)
	{
	int n_bytes = (bitlen + 7) / 8;
	int n_bits;
	int ret;
	u32 blk_size;
	u8 p_outbuf = (u8 )dout;
	u8 p_inbuf = (u8 )din;

	if (!slave)
	return -1;

	if (flags & SPI_XFER_BEGIN)
	spi_cs_activate(slave);

	while (n_bytes > 0) {
	if (n_bytes < MAX_SPI_BYTES)
	blk_size = n_bytes;
	else
	blk_size = MAX_SPI_BYTES;

	n_bits = blk_size * 8;

	ret = spi_xchg_single(slave, n_bits, p_outbuf, p_inbuf, 0);

	if (ret)
	return ret;
	if (dout)
	p_outbuf += blk_size;
	if (din)
	p_inbuf += blk_size;
	n_bytes -= blk_size;
	}

	if (flags & SPI_XFER_END) {
	spi_cs_deactivate(slave);
	}

	return 0;
	}

	void spi_init(void)
	{
	}

	static int decode_cs(struct mxc_spi_slave *mxcs, unsigned int cs)
	{
	int ret;

	/*
	* Some SPI devices require active chip-select over multiple
	* transactions, we achieve this using a GPIO. Still, the SPI
	* controller has to be configured to use one of its own chipselects.
	* To use this feature you have to call spi_setup_slave() with
	* cs = internal_cs \| (gpio << 8), and you have to use some unused
	* on this SPI controller cs between 0 and 3.
	*/
	if (cs > 3) {
	mxcs->gpio = cs >> 8;
	cs &= 3;
	ret = gpio_direction_output(mxcs->gpio, !(mxcs->ss_pol));
	if (ret) {
	printf("mxc_spi: cannot setup gpio %d\n", mxcs->gpio);
	return -EINVAL;
	}
	} else {
	mxcs->gpio = -1;
	}

	return cs;
	}

	struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	struct mxc_spi_slave *mxcs;
	int ret;

	if (bus >= ARRAY_SIZE(spi_bases))
	return NULL;

	mxcs = spi_alloc_slave(struct mxc_spi_slave, bus, cs);
	if (!mxcs) {
	puts("mxc_spi: SPI Slave not allocated !\n");
	return NULL;
	}

	mxcs->ss_pol = (mode & SPI_CS_HIGH) ? 1 : 0;

	ret = decode_cs(mxcs, cs);
	if (ret < 0) {
	free(mxcs);
	return NULL;
	}

	cs = ret;

	mxcs->base = spi_bases[bus];

	ret = spi_cfg_mxc(mxcs, cs, max_hz, mode);
	if (ret) {
	printf("mxc_spi: cannot setup SPI controller\n");
	free(mxcs);
	return NULL;
	}
	return &mxcs->slave;
	}

	void spi_free_slave(struct spi_slave *slave)
	{
	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);

	free(mxcs);
	}

	int spi_claim_bus(struct spi_slave *slave)
	{
	struct mxc_spi_slave *mxcs = to_mxc_spi_slave(slave);
	struct cspi_regs regs = (struct cspi_regs )mxcs->base;

	reg_write(&regs->rxdata, 1);
	udelay(1);
	reg_write(&regs->ctrl, mxcs->ctrl_reg);
	reg_write(&regs->period, MXC_CSPIPERIOD_32KHZ);
	reg_write(&regs->intr, 0);

	return 0;
	}

	void spi_release_bus(struct spi_slave *slave)
	{
	/* TODO: Shut the controller down */
	}