drivers/spi/tegra20_sflash.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (c) 2010-2013 NVIDIA Corporation
  * With help from the mpc8xxx SPI driver
  * With more help from omap3_spi SPI driver
  */

 #include <common.h>
 #include <dm.h>
 #include <errno.h>
 #include <log.h>
 #include <time.h>
 #include <asm/io.h>
 #include <asm/gpio.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/pinmux.h>
 #include <asm/arch-tegra/clk_rst.h>
 #include <spi.h>
 #include <fdtdec.h>
 #include "tegra_spi.h"

 DECLARE_GLOBAL_DATA_PTR;

 #define SPI_CMD_GO			BIT(30)
 #define SPI_CMD_ACTIVE_SCLK_SHIFT	26
 #define SPI_CMD_ACTIVE_SCLK_MASK	(3 << SPI_CMD_ACTIVE_SCLK_SHIFT)
 #define SPI_CMD_CK_SDA			BIT(21)
 #define SPI_CMD_ACTIVE_SDA_SHIFT	18
 #define SPI_CMD_ACTIVE_SDA_MASK		(3 << SPI_CMD_ACTIVE_SDA_SHIFT)
 #define SPI_CMD_CS_POL			BIT(16)
 #define SPI_CMD_TXEN			BIT(15)
 #define SPI_CMD_RXEN			BIT(14)
 #define SPI_CMD_CS_VAL			BIT(13)
 #define SPI_CMD_CS_SOFT			BIT(12)
 #define SPI_CMD_CS_DELAY		BIT(9)
 #define SPI_CMD_CS3_EN			BIT(8)
 #define SPI_CMD_CS2_EN			BIT(7)
 #define SPI_CMD_CS1_EN			BIT(6)
 #define SPI_CMD_CS0_EN			BIT(5)
 #define SPI_CMD_BIT_LENGTH		BIT(4)
 #define SPI_CMD_BIT_LENGTH_MASK		GENMASK(4, 0)

 #define SPI_STAT_BSY			BIT(31)
 #define SPI_STAT_RDY			BIT(30)
 #define SPI_STAT_RXF_FLUSH		BIT(29)
 #define SPI_STAT_TXF_FLUSH		BIT(28)
 #define SPI_STAT_RXF_UNR		BIT(27)
 #define SPI_STAT_TXF_OVF		BIT(26)
 #define SPI_STAT_RXF_EMPTY		BIT(25)
 #define SPI_STAT_RXF_FULL		BIT(24)
 #define SPI_STAT_TXF_EMPTY		BIT(23)
 #define SPI_STAT_TXF_FULL		BIT(22)
 #define SPI_STAT_SEL_TXRX_N		BIT(16)
 #define SPI_STAT_CUR_BLKCNT		BIT(15)

 #define SPI_TIMEOUT		1000
 #define TEGRA_SPI_MAX_FREQ	52000000

 struct spi_regs {
 	u32 command;	/* SPI_COMMAND_0 register  */
 	u32 status;	/* SPI_STATUS_0 register */
 	u32 rx_cmp;	/* SPI_RX_CMP_0 register  */
 	u32 dma_ctl;	/* SPI_DMA_CTL_0 register */
 	u32 tx_fifo;	/* SPI_TX_FIFO_0 register */
 	u32 rsvd[3];	/* offsets 0x14 to 0x1F reserved */
 	u32 rx_fifo;	/* SPI_RX_FIFO_0 register */
 };

 struct tegra20_sflash_priv {
 	struct spi_regs *regs;
 	unsigned int freq;
 	unsigned int mode;
 	int periph_id;
 	int valid;
 	int last_transaction_us;
 };

 int tegra20_sflash_cs_info(struct udevice *bus, unsigned int cs,
 			   struct spi_cs_info *info)
 {
 	/* Tegra20 SPI-Flash - only 1 device ('bus/cs') */
 	if (cs != 0)
 		return -EINVAL;
 	else
 		return 0;
 }

 static int tegra20_sflash_ofdata_to_platdata(struct udevice *bus)
 {
 	struct tegra_spi_platdata *plat = bus->platdata;
 	const void *blob = gd->fdt_blob;
 	int node = dev_of_offset(bus);

 	plat->base = devfdt_get_addr(bus);
 	plat->periph_id = clock_decode_periph_id(bus);

 	if (plat->periph_id == PERIPH_ID_NONE) {
 		debug("%s: could not decode periph id %d\n", __func__,
 		      plat->periph_id);
 		return -FDT_ERR_NOTFOUND;
 	}

 	/* Use 500KHz as a suitable default */
 	plat->frequency = fdtdec_get_int(blob, node, "spi-max-frequency",
 					500000);
 	plat->deactivate_delay_us = fdtdec_get_int(blob, node,
 					"spi-deactivate-delay", 0);
 	debug("%s: base=%#08lx, periph_id=%d, max-frequency=%d, deactivate_delay=%d\n",
 	      __func__, plat->base, plat->periph_id, plat->frequency,
 	      plat->deactivate_delay_us);

 	return 0;
 }

 static int tegra20_sflash_probe(struct udevice *bus)
 {
 	struct tegra_spi_platdata *plat = dev_get_platdata(bus);
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

 	priv->regs = (struct spi_regs *)plat->base;

 	priv->last_transaction_us = timer_get_us();
 	priv->freq = plat->frequency;
 	priv->periph_id = plat->periph_id;

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

 	return 0;
 }

 static int tegra20_sflash_claim_bus(struct udevice *dev)
 {
 	struct udevice *bus = dev->parent;
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);
 	struct spi_regs *regs = priv->regs;
 	u32 reg;

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

 	/* Clear stale status here */
 	reg = SPI_STAT_RDY | SPI_STAT_RXF_FLUSH | SPI_STAT_TXF_FLUSH | \
 		SPI_STAT_RXF_UNR | SPI_STAT_TXF_OVF;
 	writel(reg, &regs->status);
 	debug("%s: STATUS = %08x\n", __func__, readl(&regs->status));

 	/*
 	 * Use sw-controlled CS, so we can clock in data after ReadID, etc.
 	 */
 	reg = (priv->mode & 1) << SPI_CMD_ACTIVE_SDA_SHIFT;
 	if (priv->mode & 2)
 		reg |= 1 << SPI_CMD_ACTIVE_SCLK_SHIFT;
 	clrsetbits_le32(&regs->command, SPI_CMD_ACTIVE_SCLK_MASK |
 		SPI_CMD_ACTIVE_SDA_MASK, SPI_CMD_CS_SOFT | reg);
 	debug("%s: COMMAND = %08x\n", __func__, readl(&regs->command));

 	/*
 	 * SPI pins on Tegra20 are muxed - change pinmux later due to UART
 	 * issue.
 	 */
 	pinmux_set_func(PMUX_PINGRP_GMD, PMUX_FUNC_SFLASH);
 	pinmux_tristate_disable(PMUX_PINGRP_LSPI);
 	pinmux_set_func(PMUX_PINGRP_GMC, PMUX_FUNC_SFLASH);

 	return 0;
 }

 static void spi_cs_activate(struct udevice *dev)
 {
 	struct udevice *bus = dev->parent;
 	struct tegra_spi_platdata *pdata = dev_get_platdata(bus);
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

 	/* If it's too soon to do another transaction, wait */
 	if (pdata->deactivate_delay_us &&
 	    priv->last_transaction_us) {
 		ulong delay_us;		/* The delay completed so far */
 		delay_us = timer_get_us() - priv->last_transaction_us;
 		if (delay_us < pdata->deactivate_delay_us)
 			udelay(pdata->deactivate_delay_us - delay_us);
 	}

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

 static void spi_cs_deactivate(struct udevice *dev)
 {
 	struct udevice *bus = dev->parent;
 	struct tegra_spi_platdata *pdata = dev_get_platdata(bus);
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

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

 	/* Remember time of this transaction so we can honour the bus delay */
 	if (pdata->deactivate_delay_us)
 		priv->last_transaction_us = timer_get_us();
 }

 static int tegra20_sflash_xfer(struct udevice *dev, unsigned int bitlen,
 			     const void *data_out, void *data_in,
 			     unsigned long flags)
 {
 	struct udevice *bus = dev->parent;
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);
 	struct spi_regs *regs = priv->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__, bus->seq, spi_chip_select(dev), 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("spi_xfer entry: STATUS = %08x\n", reg);

 	reg = readl(&regs->command);
 	reg |= SPI_CMD_TXEN | SPI_CMD_RXEN;
 	writel(reg, &regs->command);
 	debug("spi_xfer: COMMAND = %08x\n", readl(&regs->command));

 	if (flags & SPI_XFER_BEGIN)
 		spi_cs_activate(dev);

 	/* 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];
 		}

 		num_bytes -= bytes;
 		if (dout)
 			dout += bytes;

 		clrsetbits_le32(&regs->command, SPI_CMD_BIT_LENGTH_MASK,
 				bytes * 8 - 1);
 		writel(tmpdout, &regs->tx_fifo);
 		setbits_le32(&regs->command, SPI_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 & SPI_STAT_TXF_EMPTY))
 				break;

 			if ((status & (SPI_STAT_BSY | SPI_STAT_RDY)) !=
 					SPI_STAT_RDY)
 				tm++;

 			else if (!(status & SPI_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(dev);

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

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

 	return 0;
 }

 static int tegra20_sflash_set_speed(struct udevice *bus, uint speed)
 {
 	struct tegra_spi_platdata *plat = bus->platdata;
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

 	if (speed > plat->frequency)
 		speed = plat->frequency;
 	priv->freq = speed;
 	debug("%s: regs=%p, speed=%d\n", __func__, priv->regs, priv->freq);

 	return 0;
 }

 static int tegra20_sflash_set_mode(struct udevice *bus, uint mode)
 {
 	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

 	priv->mode = mode;
 	debug("%s: regs=%p, mode=%d\n", __func__, priv->regs, priv->mode);

 	return 0;
 }

 static const struct dm_spi_ops tegra20_sflash_ops = {
 	.claim_bus	= tegra20_sflash_claim_bus,
 	.xfer		= tegra20_sflash_xfer,
 	.set_speed	= tegra20_sflash_set_speed,
 	.set_mode	= tegra20_sflash_set_mode,
 	.cs_info	= tegra20_sflash_cs_info,
 };

 static const struct udevice_id tegra20_sflash_ids[] = {
 	{ .compatible = "nvidia,tegra20-sflash" },
 	{ }
 };

 U_BOOT_DRIVER(tegra20_sflash) = {
 	.name	= "tegra20_sflash",
 	.id	= UCLASS_SPI,
 	.of_match = tegra20_sflash_ids,
 	.ops	= &tegra20_sflash_ops,
 	.ofdata_to_platdata = tegra20_sflash_ofdata_to_platdata,
 	.platdata_auto_alloc_size = sizeof(struct tegra_spi_platdata),
 	.priv_auto_alloc_size = sizeof(struct tegra20_sflash_priv),
 	.probe	= tegra20_sflash_probe,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (c) 2010-2013 NVIDIA Corporation
	* With help from the mpc8xxx SPI driver
	* With more help from omap3_spi SPI driver
	*/

	#include <common.h>
	#include <dm.h>
	#include <errno.h>
	#include <log.h>
	#include <time.h>
	#include <asm/io.h>
	#include <asm/gpio.h>
	#include <asm/arch/clock.h>
	#include <asm/arch/pinmux.h>
	#include <asm/arch-tegra/clk_rst.h>
	#include <spi.h>
	#include <fdtdec.h>
	#include "tegra_spi.h"

	DECLARE_GLOBAL_DATA_PTR;

	#define SPI_CMD_GO BIT(30)
	#define SPI_CMD_ACTIVE_SCLK_SHIFT 26
	#define SPI_CMD_ACTIVE_SCLK_MASK (3 << SPI_CMD_ACTIVE_SCLK_SHIFT)
	#define SPI_CMD_CK_SDA BIT(21)
	#define SPI_CMD_ACTIVE_SDA_SHIFT 18
	#define SPI_CMD_ACTIVE_SDA_MASK (3 << SPI_CMD_ACTIVE_SDA_SHIFT)
	#define SPI_CMD_CS_POL BIT(16)
	#define SPI_CMD_TXEN BIT(15)
	#define SPI_CMD_RXEN BIT(14)
	#define SPI_CMD_CS_VAL BIT(13)
	#define SPI_CMD_CS_SOFT BIT(12)
	#define SPI_CMD_CS_DELAY BIT(9)
	#define SPI_CMD_CS3_EN BIT(8)
	#define SPI_CMD_CS2_EN BIT(7)
	#define SPI_CMD_CS1_EN BIT(6)
	#define SPI_CMD_CS0_EN BIT(5)
	#define SPI_CMD_BIT_LENGTH BIT(4)
	#define SPI_CMD_BIT_LENGTH_MASK GENMASK(4, 0)

	#define SPI_STAT_BSY BIT(31)
	#define SPI_STAT_RDY BIT(30)
	#define SPI_STAT_RXF_FLUSH BIT(29)
	#define SPI_STAT_TXF_FLUSH BIT(28)
	#define SPI_STAT_RXF_UNR BIT(27)
	#define SPI_STAT_TXF_OVF BIT(26)
	#define SPI_STAT_RXF_EMPTY BIT(25)
	#define SPI_STAT_RXF_FULL BIT(24)
	#define SPI_STAT_TXF_EMPTY BIT(23)
	#define SPI_STAT_TXF_FULL BIT(22)
	#define SPI_STAT_SEL_TXRX_N BIT(16)
	#define SPI_STAT_CUR_BLKCNT BIT(15)

	#define SPI_TIMEOUT 1000
	#define TEGRA_SPI_MAX_FREQ 52000000

	struct spi_regs {
	u32 command; /* SPI_COMMAND_0 register */
	u32 status; /* SPI_STATUS_0 register */
	u32 rx_cmp; /* SPI_RX_CMP_0 register */
	u32 dma_ctl; /* SPI_DMA_CTL_0 register */
	u32 tx_fifo; /* SPI_TX_FIFO_0 register */
	u32 rsvd[3]; /* offsets 0x14 to 0x1F reserved */
	u32 rx_fifo; /* SPI_RX_FIFO_0 register */
	};

	struct tegra20_sflash_priv {
	struct spi_regs *regs;
	unsigned int freq;
	unsigned int mode;
	int periph_id;
	int valid;
	int last_transaction_us;
	};

	int tegra20_sflash_cs_info(struct udevice *bus, unsigned int cs,
	struct spi_cs_info *info)
	{
	/* Tegra20 SPI-Flash - only 1 device ('bus/cs') */
	if (cs != 0)
	return -EINVAL;
	else
	return 0;
	}

	static int tegra20_sflash_ofdata_to_platdata(struct udevice *bus)
	{
	struct tegra_spi_platdata *plat = bus->platdata;
	const void *blob = gd->fdt_blob;
	int node = dev_of_offset(bus);

	plat->base = devfdt_get_addr(bus);
	plat->periph_id = clock_decode_periph_id(bus);

	if (plat->periph_id == PERIPH_ID_NONE) {
	debug("%s: could not decode periph id %d\n", __func__,
	plat->periph_id);
	return -FDT_ERR_NOTFOUND;
	}

	/* Use 500KHz as a suitable default */
	plat->frequency = fdtdec_get_int(blob, node, "spi-max-frequency",
	500000);
	plat->deactivate_delay_us = fdtdec_get_int(blob, node,
	"spi-deactivate-delay", 0);
	debug("%s: base=%#08lx, periph_id=%d, max-frequency=%d, deactivate_delay=%d\n",
	__func__, plat->base, plat->periph_id, plat->frequency,
	plat->deactivate_delay_us);

	return 0;
	}

	static int tegra20_sflash_probe(struct udevice *bus)
	{
	struct tegra_spi_platdata *plat = dev_get_platdata(bus);
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

	priv->regs = (struct spi_regs *)plat->base;

	priv->last_transaction_us = timer_get_us();
	priv->freq = plat->frequency;
	priv->periph_id = plat->periph_id;

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

	return 0;
	}

	static int tegra20_sflash_claim_bus(struct udevice *dev)
	{
	struct udevice *bus = dev->parent;
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);
	struct spi_regs *regs = priv->regs;
	u32 reg;

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

	/* Clear stale status here */
	reg = SPI_STAT_RDY \| SPI_STAT_RXF_FLUSH \| SPI_STAT_TXF_FLUSH \| \
	SPI_STAT_RXF_UNR \| SPI_STAT_TXF_OVF;
	writel(reg, &regs->status);
	debug("%s: STATUS = %08x\n", __func__, readl(&regs->status));

	/*
	* Use sw-controlled CS, so we can clock in data after ReadID, etc.
	*/
	reg = (priv->mode & 1) << SPI_CMD_ACTIVE_SDA_SHIFT;
	if (priv->mode & 2)
	reg \|= 1 << SPI_CMD_ACTIVE_SCLK_SHIFT;
	clrsetbits_le32(&regs->command, SPI_CMD_ACTIVE_SCLK_MASK \|
	SPI_CMD_ACTIVE_SDA_MASK, SPI_CMD_CS_SOFT \| reg);
	debug("%s: COMMAND = %08x\n", __func__, readl(&regs->command));

	/*
	* SPI pins on Tegra20 are muxed - change pinmux later due to UART
	* issue.
	*/
	pinmux_set_func(PMUX_PINGRP_GMD, PMUX_FUNC_SFLASH);
	pinmux_tristate_disable(PMUX_PINGRP_LSPI);
	pinmux_set_func(PMUX_PINGRP_GMC, PMUX_FUNC_SFLASH);

	return 0;
	}

	static void spi_cs_activate(struct udevice *dev)
	{
	struct udevice *bus = dev->parent;
	struct tegra_spi_platdata *pdata = dev_get_platdata(bus);
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

	/* If it's too soon to do another transaction, wait */
	if (pdata->deactivate_delay_us &&
	priv->last_transaction_us) {
	ulong delay_us; /* The delay completed so far */
	delay_us = timer_get_us() - priv->last_transaction_us;
	if (delay_us < pdata->deactivate_delay_us)
	udelay(pdata->deactivate_delay_us - delay_us);
	}

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

	static void spi_cs_deactivate(struct udevice *dev)
	{
	struct udevice *bus = dev->parent;
	struct tegra_spi_platdata *pdata = dev_get_platdata(bus);
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

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

	/* Remember time of this transaction so we can honour the bus delay */
	if (pdata->deactivate_delay_us)
	priv->last_transaction_us = timer_get_us();
	}

	static int tegra20_sflash_xfer(struct udevice *dev, unsigned int bitlen,
	const void data_out, void data_in,
	unsigned long flags)
	{
	struct udevice *bus = dev->parent;
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);
	struct spi_regs *regs = priv->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__, bus->seq, spi_chip_select(dev), 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("spi_xfer entry: STATUS = %08x\n", reg);

	reg = readl(&regs->command);
	reg \|= SPI_CMD_TXEN \| SPI_CMD_RXEN;
	writel(reg, &regs->command);
	debug("spi_xfer: COMMAND = %08x\n", readl(&regs->command));

	if (flags & SPI_XFER_BEGIN)
	spi_cs_activate(dev);

	/* 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];
	}

	num_bytes -= bytes;
	if (dout)
	dout += bytes;

	clrsetbits_le32(&regs->command, SPI_CMD_BIT_LENGTH_MASK,
	bytes * 8 - 1);
	writel(tmpdout, &regs->tx_fifo);
	setbits_le32(&regs->command, SPI_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 & SPI_STAT_TXF_EMPTY))
	break;

	if ((status & (SPI_STAT_BSY \| SPI_STAT_RDY)) !=
	SPI_STAT_RDY)
	tm++;

	else if (!(status & SPI_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(dev);

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

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

	return 0;
	}

	static int tegra20_sflash_set_speed(struct udevice *bus, uint speed)
	{
	struct tegra_spi_platdata *plat = bus->platdata;
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

	if (speed > plat->frequency)
	speed = plat->frequency;
	priv->freq = speed;
	debug("%s: regs=%p, speed=%d\n", __func__, priv->regs, priv->freq);

	return 0;
	}

	static int tegra20_sflash_set_mode(struct udevice *bus, uint mode)
	{
	struct tegra20_sflash_priv *priv = dev_get_priv(bus);

	priv->mode = mode;
	debug("%s: regs=%p, mode=%d\n", __func__, priv->regs, priv->mode);

	return 0;
	}

	static const struct dm_spi_ops tegra20_sflash_ops = {
	.claim_bus = tegra20_sflash_claim_bus,
	.xfer = tegra20_sflash_xfer,
	.set_speed = tegra20_sflash_set_speed,
	.set_mode = tegra20_sflash_set_mode,
	.cs_info = tegra20_sflash_cs_info,
	};

	static const struct udevice_id tegra20_sflash_ids[] = {
	{ .compatible = "nvidia,tegra20-sflash" },
	{ }
	};

	U_BOOT_DRIVER(tegra20_sflash) = {
	.name = "tegra20_sflash",
	.id = UCLASS_SPI,
	.of_match = tegra20_sflash_ids,
	.ops = &tegra20_sflash_ops,
	.ofdata_to_platdata = tegra20_sflash_ofdata_to_platdata,
	.platdata_auto_alloc_size = sizeof(struct tegra_spi_platdata),
	.priv_auto_alloc_size = sizeof(struct tegra20_sflash_priv),
	.probe = tegra20_sflash_probe,
	};