u-boot-imx/drivers/spi/tegra20_slink.c - nest-learning-thermostat/5.0.1/u-boot - Git at Google

 /*
  * NVIDIA Tegra SPI-SLINK controller
  *
  * Copyright (c) 2010-2013 NVIDIA Corporation
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
  * may be copied, distributed, and modified under those terms.
  *
  * 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 <asm/io.h>
 #include <asm/gpio.h>
 #include <asm/arch/clock.h>
 #include <asm/arch-tegra/clk_rst.h>
 #include <asm/arch-tegra20/tegra20_slink.h>
 #include <spi.h>
 #include <fdtdec.h>

 DECLARE_GLOBAL_DATA_PTR;

 /* COMMAND */
 #define SLINK_CMD_ENB			(1 << 31)
 #define SLINK_CMD_GO			(1 << 30)
 #define SLINK_CMD_M_S			(1 << 28)
 #define SLINK_CMD_CK_SDA		(1 << 21)
 #define SLINK_CMD_CS_POL		(1 << 13)
 #define SLINK_CMD_CS_VAL		(1 << 12)
 #define SLINK_CMD_CS_SOFT		(1 << 11)
 #define SLINK_CMD_BIT_LENGTH		(1 << 4)
 #define SLINK_CMD_BIT_LENGTH_MASK	0x0000001F
 /* COMMAND2 */
 #define SLINK_CMD2_TXEN			(1 << 30)
 #define SLINK_CMD2_RXEN			(1 << 31)
 #define SLINK_CMD2_SS_EN		(1 << 18)
 #define SLINK_CMD2_SS_EN_SHIFT		18
 #define SLINK_CMD2_SS_EN_MASK		0x000C0000
 #define SLINK_CMD2_CS_ACTIVE_BETWEEN	(1 << 17)
 /* STATUS */
 #define SLINK_STAT_BSY			(1 << 31)
 #define SLINK_STAT_RDY			(1 << 30)
 #define SLINK_STAT_ERR			(1 << 29)
 #define SLINK_STAT_RXF_FLUSH		(1 << 27)
 #define SLINK_STAT_TXF_FLUSH		(1 << 26)
 #define SLINK_STAT_RXF_OVF		(1 << 25)
 #define SLINK_STAT_TXF_UNR		(1 << 24)
 #define SLINK_STAT_RXF_EMPTY		(1 << 23)
 #define SLINK_STAT_RXF_FULL		(1 << 22)
 #define SLINK_STAT_TXF_EMPTY		(1 << 21)
 #define SLINK_STAT_TXF_FULL		(1 << 20)
 #define SLINK_STAT_TXF_OVF		(1 << 19)
 #define SLINK_STAT_RXF_UNR		(1 << 18)
 #define SLINK_STAT_CUR_BLKCNT		(1 << 15)
 /* STATUS2 */
 #define SLINK_STAT2_RXF_FULL_CNT	(1 << 16)
 #define SLINK_STAT2_TXF_FULL_CNT	(1 << 0)

 #define SPI_TIMEOUT		1000
 #define TEGRA_SPI_MAX_FREQ	52000000

 struct spi_regs {
 	u32 command;	/* SLINK_COMMAND_0 register  */
 	u32 command2;	/* SLINK_COMMAND2_0 reg */
 	u32 status;	/* SLINK_STATUS_0 register */
 	u32 reserved;	/* Reserved offset 0C */
 	u32 mas_data;	/* SLINK_MAS_DATA_0 reg */
 	u32 slav_data;	/* SLINK_SLAVE_DATA_0 reg */
 	u32 dma_ctl;	/* SLINK_DMA_CTL_0 register */
 	u32 status2;	/* SLINK_STATUS2_0 reg */
 	u32 rsvd[56];	/* 0x20 to 0xFF reserved */
 	u32 tx_fifo;	/* SLINK_TX_FIFO_0 reg off 100h */
 	u32 rsvd2[31];	/* 0x104 to 0x17F reserved */
 	u32 rx_fifo;	/* SLINK_RX_FIFO_0 reg off 180h */
 };

 struct tegra_spi_ctrl {
 	struct spi_regs *regs;
 	unsigned int freq;
 	unsigned int mode;
 	int periph_id;
 	int valid;
 };

 struct tegra_spi_slave {
 	struct spi_slave slave;
 	struct tegra_spi_ctrl *ctrl;
 };

 static struct tegra_spi_ctrl spi_ctrls[CONFIG_TEGRA_SLINK_CTRLS];

 static inline struct tegra_spi_slave *to_tegra_spi(struct spi_slave *slave)
 {
 	return container_of(slave, struct tegra_spi_slave, slave);
 }

 int tegra30_spi_cs_is_valid(unsigned int bus, unsigned int cs)
 {
 	if (bus >= CONFIG_TEGRA_SLINK_CTRLS || cs > 3 || !spi_ctrls[bus].valid)
 		return 0;
 	else
 		return 1;
 }

 struct spi_slave *tegra30_spi_setup_slave(unsigned int bus, unsigned int cs,
 		unsigned int max_hz, unsigned int mode)
 {
 	struct tegra_spi_slave *spi;

 	debug("%s: bus: %u, cs: %u, max_hz: %u, mode: %u\n", __func__,
 		bus, cs, max_hz, mode);

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

 	if (max_hz > TEGRA_SPI_MAX_FREQ) {
 		printf("SPI error: unsupported frequency %d Hz. Max frequency"
 			" is %d Hz\n", max_hz, TEGRA_SPI_MAX_FREQ);
 		return NULL;
 	}

 	spi = spi_alloc_slave(struct tegra_spi_slave, bus, cs);
 	if (!spi) {
 		printf("SPI error: malloc of SPI structure failed\n");
 		return NULL;
 	}
 	spi->ctrl = &spi_ctrls[bus];
 	if (!spi->ctrl) {
 		printf("SPI error: could not find controller for bus %d\n",
 		       bus);
 		return NULL;
 	}

 	if (max_hz < spi->ctrl->freq) {
 		debug("%s: limiting frequency from %u to %u\n", __func__,
 		      spi->ctrl->freq, max_hz);
 		spi->ctrl->freq = max_hz;
 	}
 	spi->ctrl->mode = mode;

 	return &spi->slave;
 }

 void tegra30_spi_free_slave(struct spi_slave *slave)
 {
 	struct tegra_spi_slave *spi = to_tegra_spi(slave);

 	free(spi);
 }

 int tegra30_spi_init(int *node_list, int count)
 {
 	struct tegra_spi_ctrl *ctrl;
 	int i;
 	int node = 0;
 	int found = 0;

 	for (i = 0; i < count; i++) {
 		ctrl = &spi_ctrls[i];
 		node = node_list[i];

 		ctrl->regs = (struct spi_regs *)fdtdec_get_addr(gd->fdt_blob,
 								node, "reg");
 		if ((fdt_addr_t)ctrl->regs == FDT_ADDR_T_NONE) {
 			debug("%s: no slink register found\n", __func__);
 			continue;
 		}
 		ctrl->freq = fdtdec_get_int(gd->fdt_blob, node,
 					    "spi-max-frequency", 0);
 		if (!ctrl->freq) {
 			debug("%s: no slink max frequency found\n", __func__);
 			continue;
 		}

 		ctrl->periph_id = clock_decode_periph_id(gd->fdt_blob, node);
 		if (ctrl->periph_id == PERIPH_ID_NONE) {
 			debug("%s: could not decode periph id\n", __func__);
 			continue;
 		}
 		ctrl->valid = 1;
 		found = 1;

 		debug("%s: found controller at %p, freq = %u, periph_id = %d\n",
 		      __func__, ctrl->regs, ctrl->freq, ctrl->periph_id);
 	}
 	return !found;
 }

 int tegra30_spi_claim_bus(struct spi_slave *slave)
 {
 	struct tegra_spi_slave *spi = to_tegra_spi(slave);
 	struct spi_regs *regs = spi->ctrl->regs;
 	u32 reg;

 	/* Change SPI clock to correct frequency, PLLP_OUT0 source */
 	clock_start_periph_pll(spi->ctrl->periph_id, CLOCK_ID_PERIPH,
 			       spi->ctrl->freq);

 	/* Clear stale status here */
 	reg = SLINK_STAT_RDY | SLINK_STAT_RXF_FLUSH | SLINK_STAT_TXF_FLUSH | \
 		SLINK_STAT_RXF_UNR | SLINK_STAT_TXF_OVF;
 	writel(reg, &regs->status);
 	debug("%s: STATUS = %08x\n", __func__, readl(&regs->status));

 	/* Set master mode and sw controlled CS */
 	reg = readl(&regs->command);
 	reg |= SLINK_CMD_M_S | SLINK_CMD_CS_SOFT;
 	writel(reg, &regs->command);
 	debug("%s: COMMAND = %08x\n", __func__, readl(&regs->command));

 	return 0;
 }

 void tegra30_spi_cs_activate(struct spi_slave *slave)
 {
 	struct tegra_spi_slave *spi = to_tegra_spi(slave);
 	struct spi_regs *regs = spi->ctrl->regs;

 	/* CS is negated on Tegra, so drive a 1 to get a 0 */
 	setbits_le32(&regs->command, SLINK_CMD_CS_VAL);
 }

 void tegra30_spi_cs_deactivate(struct spi_slave *slave)
 {
 	struct tegra_spi_slave *spi = to_tegra_spi(slave);
 	struct spi_regs *regs = spi->ctrl->regs;

 	/* CS is negated on Tegra, so drive a 0 to get a 1 */
 	clrbits_le32(&regs->command, SLINK_CMD_CS_VAL);
 }

 int tegra30_spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 		const void *data_out, void *data_in, unsigned long flags)
 {
 	struct tegra_spi_slave *spi = to_tegra_spi(slave);
 	struct spi_regs *regs = spi->ctrl->regs;
 	u32 reg, tmpdout, tmpdin = 0;
 	const u8 *dout = data_out;
 	u8 *din = data_in;
 	int num_bytes;
 	int ret;

 	debug("%s: slave %u:%u dout %p din %p bitlen %u\n",
 	      __func__, slave->bus, slave->cs, dout, din, bitlen);
 	if (bitlen % 8)
 		return -1;
 	num_bytes = bitlen / 8;

 	ret = 0;

 	reg = readl(&regs->status);
 	writel(reg, &regs->status);	/* Clear all SPI events via R/W */
 	debug("%s entry: STATUS = %08x\n", __func__, reg);

 	reg = readl(&regs->status2);
 	writel(reg, &regs->status2);	/* Clear all STATUS2 events via R/W */
 	debug("%s entry: STATUS2 = %08x\n", __func__, reg);

 	debug("%s entry: COMMAND = %08x\n", __func__, readl(&regs->command));

 	clrsetbits_le32(&regs->command2, SLINK_CMD2_SS_EN_MASK,
 			SLINK_CMD2_TXEN | SLINK_CMD2_RXEN |
 			(slave->cs << SLINK_CMD2_SS_EN_SHIFT));
 	debug("%s entry: COMMAND2 = %08x\n", __func__, readl(&regs->command2));

 	if (flags & SPI_XFER_BEGIN)
 		spi_cs_activate(slave);

 	/* handle data in 32-bit chunks */
 	while (num_bytes > 0) {
 		int bytes;
 		int is_read = 0;
 		int tm, i;

 		tmpdout = 0;
 		bytes = (num_bytes > 4) ?  4 : num_bytes;

 		if (dout != NULL) {
 			for (i = 0; i < bytes; ++i)
 				tmpdout = (tmpdout << 8) | dout[i];
 			dout += bytes;
 		}

 		num_bytes -= bytes;

 		clrsetbits_le32(&regs->command, SLINK_CMD_BIT_LENGTH_MASK,
 				bytes * 8 - 1);
 		writel(tmpdout, &regs->tx_fifo);
 		setbits_le32(&regs->command, SLINK_CMD_GO);

 		/*
 		 * Wait for SPI transmit FIFO to empty, or to time out.
 		 * The RX FIFO status will be read and cleared last
 		 */
 		for (tm = 0, is_read = 0; tm < SPI_TIMEOUT; ++tm) {
 			u32 status;

 			status = readl(&regs->status);

 			/* We can exit when we've had both RX and TX activity */
 			if (is_read && (status & SLINK_STAT_TXF_EMPTY))
 				break;

 			if ((status & (SLINK_STAT_BSY | SLINK_STAT_RDY)) !=
 					SLINK_STAT_RDY)
 				tm++;

 			else if (!(status & SLINK_STAT_RXF_EMPTY)) {
 				tmpdin = readl(&regs->rx_fifo);
 				is_read = 1;

 				/* swap bytes read in */
 				if (din != NULL) {
 					for (i = bytes - 1; i >= 0; --i) {
 						din[i] = tmpdin & 0xff;
 						tmpdin >>= 8;
 					}
 					din += bytes;
 				}
 			}
 		}

 		if (tm >= SPI_TIMEOUT)
 			ret = tm;

 		/* clear ACK RDY, etc. bits */
 		writel(readl(&regs->status), &regs->status);
 	}

 	if (flags & SPI_XFER_END)
 		spi_cs_deactivate(slave);

 	debug("%s: transfer ended. Value=%08x, status = %08x\n",
 	      __func__, tmpdin, readl(&regs->status));

 	if (ret) {
 		printf("%s: timeout during SPI transfer, tm %d\n",
 		       __func__, ret);
 		return -1;
 	}

 	return 0;
 }
	/*
	* NVIDIA Tegra SPI-SLINK controller
	*
	* Copyright (c) 2010-2013 NVIDIA Corporation
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* This software is licensed under the terms of the GNU General Public
	* License version 2, as published by the Free Software Foundation, and
	* may be copied, distributed, and modified under those terms.
	*
	* 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 <asm/io.h>
	#include <asm/gpio.h>
	#include <asm/arch/clock.h>
	#include <asm/arch-tegra/clk_rst.h>
	#include <asm/arch-tegra20/tegra20_slink.h>
	#include <spi.h>
	#include <fdtdec.h>

	DECLARE_GLOBAL_DATA_PTR;

	/* COMMAND */
	#define SLINK_CMD_ENB (1 << 31)
	#define SLINK_CMD_GO (1 << 30)
	#define SLINK_CMD_M_S (1 << 28)
	#define SLINK_CMD_CK_SDA (1 << 21)
	#define SLINK_CMD_CS_POL (1 << 13)
	#define SLINK_CMD_CS_VAL (1 << 12)
	#define SLINK_CMD_CS_SOFT (1 << 11)
	#define SLINK_CMD_BIT_LENGTH (1 << 4)
	#define SLINK_CMD_BIT_LENGTH_MASK 0x0000001F
	/* COMMAND2 */
	#define SLINK_CMD2_TXEN (1 << 30)
	#define SLINK_CMD2_RXEN (1 << 31)
	#define SLINK_CMD2_SS_EN (1 << 18)
	#define SLINK_CMD2_SS_EN_SHIFT 18
	#define SLINK_CMD2_SS_EN_MASK 0x000C0000
	#define SLINK_CMD2_CS_ACTIVE_BETWEEN (1 << 17)
	/* STATUS */
	#define SLINK_STAT_BSY (1 << 31)
	#define SLINK_STAT_RDY (1 << 30)
	#define SLINK_STAT_ERR (1 << 29)
	#define SLINK_STAT_RXF_FLUSH (1 << 27)
	#define SLINK_STAT_TXF_FLUSH (1 << 26)
	#define SLINK_STAT_RXF_OVF (1 << 25)
	#define SLINK_STAT_TXF_UNR (1 << 24)
	#define SLINK_STAT_RXF_EMPTY (1 << 23)
	#define SLINK_STAT_RXF_FULL (1 << 22)
	#define SLINK_STAT_TXF_EMPTY (1 << 21)
	#define SLINK_STAT_TXF_FULL (1 << 20)
	#define SLINK_STAT_TXF_OVF (1 << 19)
	#define SLINK_STAT_RXF_UNR (1 << 18)
	#define SLINK_STAT_CUR_BLKCNT (1 << 15)
	/* STATUS2 */
	#define SLINK_STAT2_RXF_FULL_CNT (1 << 16)
	#define SLINK_STAT2_TXF_FULL_CNT (1 << 0)

	#define SPI_TIMEOUT 1000
	#define TEGRA_SPI_MAX_FREQ 52000000

	struct spi_regs {
	u32 command; /* SLINK_COMMAND_0 register */
	u32 command2; /* SLINK_COMMAND2_0 reg */
	u32 status; /* SLINK_STATUS_0 register */
	u32 reserved; /* Reserved offset 0C */
	u32 mas_data; /* SLINK_MAS_DATA_0 reg */
	u32 slav_data; /* SLINK_SLAVE_DATA_0 reg */
	u32 dma_ctl; /* SLINK_DMA_CTL_0 register */
	u32 status2; /* SLINK_STATUS2_0 reg */
	u32 rsvd[56]; /* 0x20 to 0xFF reserved */
	u32 tx_fifo; /* SLINK_TX_FIFO_0 reg off 100h */
	u32 rsvd2[31]; /* 0x104 to 0x17F reserved */
	u32 rx_fifo; /* SLINK_RX_FIFO_0 reg off 180h */
	};

	struct tegra_spi_ctrl {
	struct spi_regs *regs;
	unsigned int freq;
	unsigned int mode;
	int periph_id;
	int valid;
	};

	struct tegra_spi_slave {
	struct spi_slave slave;
	struct tegra_spi_ctrl *ctrl;
	};

	static struct tegra_spi_ctrl spi_ctrls[CONFIG_TEGRA_SLINK_CTRLS];

	static inline struct tegra_spi_slave to_tegra_spi(struct spi_slave slave)
	{
	return container_of(slave, struct tegra_spi_slave, slave);
	}

	int tegra30_spi_cs_is_valid(unsigned int bus, unsigned int cs)
	{
	if (bus >= CONFIG_TEGRA_SLINK_CTRLS \|\| cs > 3 \|\| !spi_ctrls[bus].valid)
	return 0;
	else
	return 1;
	}

	struct spi_slave *tegra30_spi_setup_slave(unsigned int bus, unsigned int cs,
	unsigned int max_hz, unsigned int mode)
	{
	struct tegra_spi_slave *spi;

	debug("%s: bus: %u, cs: %u, max_hz: %u, mode: %u\n", __func__,
	bus, cs, max_hz, mode);

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

	if (max_hz > TEGRA_SPI_MAX_FREQ) {
	printf("SPI error: unsupported frequency %d Hz. Max frequency"
	" is %d Hz\n", max_hz, TEGRA_SPI_MAX_FREQ);
	return NULL;
	}

	spi = spi_alloc_slave(struct tegra_spi_slave, bus, cs);
	if (!spi) {
	printf("SPI error: malloc of SPI structure failed\n");
	return NULL;
	}
	spi->ctrl = &spi_ctrls[bus];
	if (!spi->ctrl) {
	printf("SPI error: could not find controller for bus %d\n",
	bus);
	return NULL;
	}

	if (max_hz < spi->ctrl->freq) {
	debug("%s: limiting frequency from %u to %u\n", __func__,
	spi->ctrl->freq, max_hz);
	spi->ctrl->freq = max_hz;
	}
	spi->ctrl->mode = mode;

	return &spi->slave;
	}

	void tegra30_spi_free_slave(struct spi_slave *slave)
	{
	struct tegra_spi_slave *spi = to_tegra_spi(slave);

	free(spi);
	}

	int tegra30_spi_init(int *node_list, int count)
	{
	struct tegra_spi_ctrl *ctrl;
	int i;
	int node = 0;
	int found = 0;

	for (i = 0; i < count; i++) {
	ctrl = &spi_ctrls[i];
	node = node_list[i];

	ctrl->regs = (struct spi_regs *)fdtdec_get_addr(gd->fdt_blob,
	node, "reg");
	if ((fdt_addr_t)ctrl->regs == FDT_ADDR_T_NONE) {
	debug("%s: no slink register found\n", __func__);
	continue;
	}
	ctrl->freq = fdtdec_get_int(gd->fdt_blob, node,
	"spi-max-frequency", 0);
	if (!ctrl->freq) {
	debug("%s: no slink max frequency found\n", __func__);
	continue;
	}

	ctrl->periph_id = clock_decode_periph_id(gd->fdt_blob, node);
	if (ctrl->periph_id == PERIPH_ID_NONE) {
	debug("%s: could not decode periph id\n", __func__);
	continue;
	}
	ctrl->valid = 1;
	found = 1;

	debug("%s: found controller at %p, freq = %u, periph_id = %d\n",
	__func__, ctrl->regs, ctrl->freq, ctrl->periph_id);
	}
	return !found;
	}

	int tegra30_spi_claim_bus(struct spi_slave *slave)
	{
	struct tegra_spi_slave *spi = to_tegra_spi(slave);
	struct spi_regs *regs = spi->ctrl->regs;
	u32 reg;

	/* Change SPI clock to correct frequency, PLLP_OUT0 source */
	clock_start_periph_pll(spi->ctrl->periph_id, CLOCK_ID_PERIPH,
	spi->ctrl->freq);

	/* Clear stale status here */
	reg = SLINK_STAT_RDY \| SLINK_STAT_RXF_FLUSH \| SLINK_STAT_TXF_FLUSH \| \
	SLINK_STAT_RXF_UNR \| SLINK_STAT_TXF_OVF;
	writel(reg, &regs->status);
	debug("%s: STATUS = %08x\n", __func__, readl(&regs->status));

	/* Set master mode and sw controlled CS */
	reg = readl(&regs->command);
	reg \|= SLINK_CMD_M_S \| SLINK_CMD_CS_SOFT;
	writel(reg, &regs->command);
	debug("%s: COMMAND = %08x\n", __func__, readl(&regs->command));

	return 0;
	}

	void tegra30_spi_cs_activate(struct spi_slave *slave)
	{
	struct tegra_spi_slave *spi = to_tegra_spi(slave);
	struct spi_regs *regs = spi->ctrl->regs;

	/* CS is negated on Tegra, so drive a 1 to get a 0 */
	setbits_le32(&regs->command, SLINK_CMD_CS_VAL);
	}

	void tegra30_spi_cs_deactivate(struct spi_slave *slave)
	{
	struct tegra_spi_slave *spi = to_tegra_spi(slave);
	struct spi_regs *regs = spi->ctrl->regs;

	/* CS is negated on Tegra, so drive a 0 to get a 1 */
	clrbits_le32(&regs->command, SLINK_CMD_CS_VAL);
	}

	int tegra30_spi_xfer(struct spi_slave *slave, unsigned int bitlen,
	const void data_out, void data_in, unsigned long flags)
	{
	struct tegra_spi_slave *spi = to_tegra_spi(slave);
	struct spi_regs *regs = spi->ctrl->regs;
	u32 reg, tmpdout, tmpdin = 0;
	const u8 *dout = data_out;
	u8 *din = data_in;
	int num_bytes;
	int ret;

	debug("%s: slave %u:%u dout %p din %p bitlen %u\n",
	__func__, slave->bus, slave->cs, dout, din, bitlen);
	if (bitlen % 8)
	return -1;
	num_bytes = bitlen / 8;

	ret = 0;

	reg = readl(&regs->status);
	writel(reg, &regs->status); /* Clear all SPI events via R/W */
	debug("%s entry: STATUS = %08x\n", __func__, reg);

	reg = readl(&regs->status2);
	writel(reg, &regs->status2); /* Clear all STATUS2 events via R/W */
	debug("%s entry: STATUS2 = %08x\n", __func__, reg);

	debug("%s entry: COMMAND = %08x\n", __func__, readl(&regs->command));

	clrsetbits_le32(&regs->command2, SLINK_CMD2_SS_EN_MASK,
	SLINK_CMD2_TXEN \| SLINK_CMD2_RXEN \|
	(slave->cs << SLINK_CMD2_SS_EN_SHIFT));
	debug("%s entry: COMMAND2 = %08x\n", __func__, readl(&regs->command2));

	if (flags & SPI_XFER_BEGIN)
	spi_cs_activate(slave);

	/* handle data in 32-bit chunks */
	while (num_bytes > 0) {
	int bytes;
	int is_read = 0;
	int tm, i;

	tmpdout = 0;
	bytes = (num_bytes > 4) ? 4 : num_bytes;

	if (dout != NULL) {
	for (i = 0; i < bytes; ++i)
	tmpdout = (tmpdout << 8) \| dout[i];
	dout += bytes;
	}

	num_bytes -= bytes;

	clrsetbits_le32(&regs->command, SLINK_CMD_BIT_LENGTH_MASK,
	bytes * 8 - 1);
	writel(tmpdout, &regs->tx_fifo);
	setbits_le32(&regs->command, SLINK_CMD_GO);

	/*
	* Wait for SPI transmit FIFO to empty, or to time out.
	* The RX FIFO status will be read and cleared last
	*/
	for (tm = 0, is_read = 0; tm < SPI_TIMEOUT; ++tm) {
	u32 status;

	status = readl(&regs->status);

	/* We can exit when we've had both RX and TX activity */
	if (is_read && (status & SLINK_STAT_TXF_EMPTY))
	break;

	if ((status & (SLINK_STAT_BSY \| SLINK_STAT_RDY)) !=
	SLINK_STAT_RDY)
	tm++;

	else if (!(status & SLINK_STAT_RXF_EMPTY)) {
	tmpdin = readl(&regs->rx_fifo);
	is_read = 1;

	/* swap bytes read in */
	if (din != NULL) {
	for (i = bytes - 1; i >= 0; --i) {
	din[i] = tmpdin & 0xff;
	tmpdin >>= 8;
	}
	din += bytes;
	}
	}
	}

	if (tm >= SPI_TIMEOUT)
	ret = tm;

	/* clear ACK RDY, etc. bits */
	writel(readl(&regs->status), &regs->status);
	}

	if (flags & SPI_XFER_END)
	spi_cs_deactivate(slave);

	debug("%s: transfer ended. Value=%08x, status = %08x\n",
	__func__, tmpdin, readl(&regs->status));

	if (ret) {
	printf("%s: timeout during SPI transfer, tm %d\n",
	__func__, ret);
	return -1;
	}

	return 0;
	}