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

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2007 Atmel Corporation
  */
 #include <common.h>
 #include <clk.h>
 #include <dm.h>
 #include <fdtdec.h>
 #include <spi.h>
 #include <malloc.h>
 #include <wait_bit.h>
 #include <asm/io.h>
 #include <asm/arch/clk.h>
 #include <asm/arch/hardware.h>
 #include <asm/arch/at91_spi.h>
 #if CONFIG_IS_ENABLED(DM_GPIO)
 #include <asm/gpio.h>
 #endif
 #include <linux/bitops.h>
 #include <linux/printk.h>

 /*
  * Register definitions for the Atmel AT32/AT91 SPI Controller
  */
 /* Register offsets */
 #define ATMEL_SPI_CR			0x0000
 #define ATMEL_SPI_MR			0x0004
 #define ATMEL_SPI_RDR			0x0008
 #define ATMEL_SPI_TDR			0x000c
 #define ATMEL_SPI_SR			0x0010
 #define ATMEL_SPI_IER			0x0014
 #define ATMEL_SPI_IDR			0x0018
 #define ATMEL_SPI_IMR			0x001c
 #define ATMEL_SPI_CSR(x)		(0x0030 + 4 * (x))
 #define ATMEL_SPI_VERSION		0x00fc

 /* Bits in CR */
 #define ATMEL_SPI_CR_SPIEN		BIT(0)
 #define ATMEL_SPI_CR_SPIDIS		BIT(1)
 #define ATMEL_SPI_CR_SWRST		BIT(7)
 #define ATMEL_SPI_CR_LASTXFER		BIT(24)

 /* Bits in MR */
 #define ATMEL_SPI_MR_MSTR		BIT(0)
 #define ATMEL_SPI_MR_PS			BIT(1)
 #define ATMEL_SPI_MR_PCSDEC		BIT(2)
 #define ATMEL_SPI_MR_FDIV		BIT(3)
 #define ATMEL_SPI_MR_MODFDIS		BIT(4)
 #define ATMEL_SPI_MR_WDRBT		BIT(5)
 #define ATMEL_SPI_MR_LLB		BIT(7)
 #define ATMEL_SPI_MR_PCS(x)		(((x) & 15) << 16)
 #define ATMEL_SPI_MR_DLYBCS(x)		((x) << 24)

 /* Bits in RDR */
 #define ATMEL_SPI_RDR_RD(x)		(x)
 #define ATMEL_SPI_RDR_PCS(x)		((x) << 16)

 /* Bits in TDR */
 #define ATMEL_SPI_TDR_TD(x)		(x)
 #define ATMEL_SPI_TDR_PCS(x)		((x) << 16)
 #define ATMEL_SPI_TDR_LASTXFER		BIT(24)

 /* Bits in SR/IER/IDR/IMR */
 #define ATMEL_SPI_SR_RDRF		BIT(0)
 #define ATMEL_SPI_SR_TDRE		BIT(1)
 #define ATMEL_SPI_SR_MODF		BIT(2)
 #define ATMEL_SPI_SR_OVRES		BIT(3)
 #define ATMEL_SPI_SR_ENDRX		BIT(4)
 #define ATMEL_SPI_SR_ENDTX		BIT(5)
 #define ATMEL_SPI_SR_RXBUFF		BIT(6)
 #define ATMEL_SPI_SR_TXBUFE		BIT(7)
 #define ATMEL_SPI_SR_NSSR		BIT(8)
 #define ATMEL_SPI_SR_TXEMPTY		BIT(9)
 #define ATMEL_SPI_SR_SPIENS		BIT(16)

 /* Bits in CSRx */
 #define ATMEL_SPI_CSRx_CPOL		BIT(0)
 #define ATMEL_SPI_CSRx_NCPHA		BIT(1)
 #define ATMEL_SPI_CSRx_CSAAT		BIT(3)
 #define ATMEL_SPI_CSRx_BITS(x)		((x) << 4)
 #define ATMEL_SPI_CSRx_SCBR(x)		((x) << 8)
 #define ATMEL_SPI_CSRx_SCBR_MAX		GENMASK(7, 0)
 #define ATMEL_SPI_CSRx_DLYBS(x)		((x) << 16)
 #define ATMEL_SPI_CSRx_DLYBCT(x)	((x) << 24)

 /* Bits in VERSION */
 #define ATMEL_SPI_VERSION_REV(x)	((x) & 0xfff)
 #define ATMEL_SPI_VERSION_MFN(x)	((x) << 16)

 /* Constants for CSRx:BITS */
 #define ATMEL_SPI_BITS_8		0
 #define ATMEL_SPI_BITS_9		1
 #define ATMEL_SPI_BITS_10		2
 #define ATMEL_SPI_BITS_11		3
 #define ATMEL_SPI_BITS_12		4
 #define ATMEL_SPI_BITS_13		5
 #define ATMEL_SPI_BITS_14		6
 #define ATMEL_SPI_BITS_15		7
 #define ATMEL_SPI_BITS_16		8

 #define MAX_CS_COUNT	4

 /* Register access macros */
 #define spi_readl(as, reg)					\
 	readl(as->regs + ATMEL_SPI_##reg)
 #define spi_writel(as, reg, value)				\
 	writel(value, as->regs + ATMEL_SPI_##reg)

 struct atmel_spi_plat {
 	struct at91_spi *regs;
 };

 struct atmel_spi_priv {
 	unsigned int freq;		/* Default frequency */
 	unsigned int mode;
 	ulong bus_clk_rate;
 #if CONFIG_IS_ENABLED(DM_GPIO)
 	struct gpio_desc cs_gpios[MAX_CS_COUNT];
 #endif
 };

 static int atmel_spi_claim_bus(struct udevice *dev)
 {
 	struct udevice *bus = dev_get_parent(dev);
 	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
 	struct atmel_spi_priv *priv = dev_get_priv(bus);
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 	struct at91_spi *reg_base = bus_plat->regs;
 	u32 cs = slave_plat->cs;
 	u32 freq = priv->freq;
 	u32 scbr, csrx, mode;

 	scbr = (priv->bus_clk_rate + freq - 1) / freq;
 	if (scbr > ATMEL_SPI_CSRx_SCBR_MAX)
 		return -EINVAL;

 	if (scbr < 1)
 		scbr = 1;

 	csrx = ATMEL_SPI_CSRx_SCBR(scbr);
 	csrx |= ATMEL_SPI_CSRx_BITS(ATMEL_SPI_BITS_8);

 	if (!(priv->mode & SPI_CPHA))
 		csrx |= ATMEL_SPI_CSRx_NCPHA;
 	if (priv->mode & SPI_CPOL)
 		csrx |= ATMEL_SPI_CSRx_CPOL;

 	writel(csrx, &reg_base->csr[cs]);

 	mode = ATMEL_SPI_MR_MSTR |
 	       ATMEL_SPI_MR_MODFDIS |
 	       ATMEL_SPI_MR_WDRBT |
 	       ATMEL_SPI_MR_PCS(~(1 << cs));

 	writel(mode, &reg_base->mr);

 	writel(ATMEL_SPI_CR_SPIEN, &reg_base->cr);

 	return 0;
 }

 static int atmel_spi_release_bus(struct udevice *dev)
 {
 	struct udevice *bus = dev_get_parent(dev);
 	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);

 	writel(ATMEL_SPI_CR_SPIDIS, &bus_plat->regs->cr);

 	return 0;
 }

 static void atmel_spi_cs_activate(struct udevice *dev)
 {
 #if CONFIG_IS_ENABLED(DM_GPIO)
 	struct udevice *bus = dev_get_parent(dev);
 	struct atmel_spi_priv *priv = dev_get_priv(bus);
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 	u32 cs = slave_plat->cs;

 	if (!dm_gpio_is_valid(&priv->cs_gpios[cs]))
 		return;

 	dm_gpio_set_value(&priv->cs_gpios[cs], 0);
 #endif
 }

 static void atmel_spi_cs_deactivate(struct udevice *dev)
 {
 #if CONFIG_IS_ENABLED(DM_GPIO)
 	struct udevice *bus = dev_get_parent(dev);
 	struct atmel_spi_priv *priv = dev_get_priv(bus);
 	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
 	u32 cs = slave_plat->cs;

 	if (!dm_gpio_is_valid(&priv->cs_gpios[cs]))
 		return;

 	dm_gpio_set_value(&priv->cs_gpios[cs], 1);
 #endif
 }

 static int atmel_spi_xfer(struct udevice *dev, unsigned int bitlen,
 			  const void *dout, void *din, unsigned long flags)
 {
 	struct udevice *bus = dev_get_parent(dev);
 	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
 	struct at91_spi *reg_base = bus_plat->regs;

 	u32 len_tx, len_rx, len;
 	u32 status;
 	const u8 *txp = dout;
 	u8 *rxp = din;
 	u8 value;

 	if (bitlen == 0)
 		goto out;

 	/*
 	 * The controller can do non-multiple-of-8 bit
 	 * transfers, but this driver currently doesn't support it.
 	 *
 	 * It's also not clear how such transfers are supposed to be
 	 * represented as a stream of bytes...this is a limitation of
 	 * the current SPI interface.
 	 */
 	if (bitlen % 8) {
 		/* Errors always terminate an ongoing transfer */
 		flags |= SPI_XFER_END;
 		goto out;
 	}

 	len = bitlen / 8;

 	/*
 	 * The controller can do automatic CS control, but it is
 	 * somewhat quirky, and it doesn't really buy us much anyway
 	 * in the context of U-Boot.
 	 */
 	if (flags & SPI_XFER_BEGIN) {
 		atmel_spi_cs_activate(dev);

 		/*
 		 * sometimes the RDR is not empty when we get here,
 		 * in theory that should not happen, but it DOES happen.
 		 * Read it here to be on the safe side.
 		 * That also clears the OVRES flag. Required if the
 		 * following loop exits due to OVRES!
 		 */
 		readl(&reg_base->rdr);
 	}

 	for (len_tx = 0, len_rx = 0; len_rx < len; ) {
 		status = readl(&reg_base->sr);

 		if (status & ATMEL_SPI_SR_OVRES)
 			return -1;

 		if ((len_tx < len) && (status & ATMEL_SPI_SR_TDRE)) {
 			if (txp)
 				value = *txp++;
 			else
 				value = 0;
 			writel(value, &reg_base->tdr);
 			len_tx++;
 		}

 		if (status & ATMEL_SPI_SR_RDRF) {
 			value = readl(&reg_base->rdr);
 			if (rxp)
 				*rxp++ = value;
 			len_rx++;
 		}
 	}

 out:
 	if (flags & SPI_XFER_END) {
 		/*
 		 * Wait until the transfer is completely done before
 		 * we deactivate CS.
 		 */
 		wait_for_bit_le32(&reg_base->sr,
 				  ATMEL_SPI_SR_TXEMPTY, true, 1000, false);

 		atmel_spi_cs_deactivate(dev);
 	}

 	return 0;
 }

 static int atmel_spi_set_speed(struct udevice *bus, uint speed)
 {
 	struct atmel_spi_priv *priv = dev_get_priv(bus);

 	priv->freq = speed;

 	return 0;
 }

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

 	priv->mode = mode;

 	return 0;
 }

 static const struct dm_spi_ops atmel_spi_ops = {
 	.claim_bus	= atmel_spi_claim_bus,
 	.release_bus	= atmel_spi_release_bus,
 	.xfer		= atmel_spi_xfer,
 	.set_speed	= atmel_spi_set_speed,
 	.set_mode	= atmel_spi_set_mode,
 	/*
 	 * cs_info is not needed, since we require all chip selects to be
 	 * in the device tree explicitly
 	 */
 };

 static int atmel_spi_enable_clk(struct udevice *bus)
 {
 	struct atmel_spi_priv *priv = dev_get_priv(bus);
 	struct clk clk;
 	ulong clk_rate;
 	int ret;

 	ret = clk_get_by_index(bus, 0, &clk);
 	if (ret)
 		return -EINVAL;

 	ret = clk_enable(&clk);
 	if (ret)
 		return ret;

 	clk_rate = clk_get_rate(&clk);
 	if (!clk_rate)
 		return -EINVAL;

 	priv->bus_clk_rate = clk_rate;

 	return 0;
 }

 static int atmel_spi_probe(struct udevice *bus)
 {
 	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
 	int ret;

 	ret = atmel_spi_enable_clk(bus);
 	if (ret)
 		return ret;

 	bus_plat->regs = dev_read_addr_ptr(bus);

 #if CONFIG_IS_ENABLED(DM_GPIO)
 	struct atmel_spi_priv *priv = dev_get_priv(bus);
 	int i;

 	ret = gpio_request_list_by_name(bus, "cs-gpios", priv->cs_gpios,
 					ARRAY_SIZE(priv->cs_gpios), 0);
 	if (ret < 0) {
 		pr_err("Can't get %s gpios! Error: %d", bus->name, ret);
 		return ret;
 	}

 	for(i = 0; i < ARRAY_SIZE(priv->cs_gpios); i++) {
 		if (!dm_gpio_is_valid(&priv->cs_gpios[i]))
 			continue;

 		dm_gpio_set_dir_flags(&priv->cs_gpios[i],
 				      GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
 	}
 #endif

 	writel(ATMEL_SPI_CR_SWRST, &bus_plat->regs->cr);

 	return 0;
 }

 static const struct udevice_id atmel_spi_ids[] = {
 	{ .compatible = "atmel,at91rm9200-spi" },
 	{ }
 };

 U_BOOT_DRIVER(atmel_spi) = {
 	.name	= "atmel_spi",
 	.id	= UCLASS_SPI,
 	.of_match = atmel_spi_ids,
 	.ops	= &atmel_spi_ops,
 	.plat_auto	= sizeof(struct atmel_spi_plat),
 	.priv_auto	= sizeof(struct atmel_spi_priv),
 	.probe	= atmel_spi_probe,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (C) 2007 Atmel Corporation
	*/
	#include <common.h>
	#include <clk.h>
	#include <dm.h>
	#include <fdtdec.h>
	#include <spi.h>
	#include <malloc.h>
	#include <wait_bit.h>
	#include <asm/io.h>
	#include <asm/arch/clk.h>
	#include <asm/arch/hardware.h>
	#include <asm/arch/at91_spi.h>
	#if CONFIG_IS_ENABLED(DM_GPIO)
	#include <asm/gpio.h>
	#endif
	#include <linux/bitops.h>
	#include <linux/printk.h>

	/*
	* Register definitions for the Atmel AT32/AT91 SPI Controller
	*/
	/* Register offsets */
	#define ATMEL_SPI_CR 0x0000
	#define ATMEL_SPI_MR 0x0004
	#define ATMEL_SPI_RDR 0x0008
	#define ATMEL_SPI_TDR 0x000c
	#define ATMEL_SPI_SR 0x0010
	#define ATMEL_SPI_IER 0x0014
	#define ATMEL_SPI_IDR 0x0018
	#define ATMEL_SPI_IMR 0x001c
	#define ATMEL_SPI_CSR(x) (0x0030 + 4 * (x))
	#define ATMEL_SPI_VERSION 0x00fc

	/* Bits in CR */
	#define ATMEL_SPI_CR_SPIEN BIT(0)
	#define ATMEL_SPI_CR_SPIDIS BIT(1)
	#define ATMEL_SPI_CR_SWRST BIT(7)
	#define ATMEL_SPI_CR_LASTXFER BIT(24)

	/* Bits in MR */
	#define ATMEL_SPI_MR_MSTR BIT(0)
	#define ATMEL_SPI_MR_PS BIT(1)
	#define ATMEL_SPI_MR_PCSDEC BIT(2)
	#define ATMEL_SPI_MR_FDIV BIT(3)
	#define ATMEL_SPI_MR_MODFDIS BIT(4)
	#define ATMEL_SPI_MR_WDRBT BIT(5)
	#define ATMEL_SPI_MR_LLB BIT(7)
	#define ATMEL_SPI_MR_PCS(x) (((x) & 15) << 16)
	#define ATMEL_SPI_MR_DLYBCS(x) ((x) << 24)

	/* Bits in RDR */
	#define ATMEL_SPI_RDR_RD(x) (x)
	#define ATMEL_SPI_RDR_PCS(x) ((x) << 16)

	/* Bits in TDR */
	#define ATMEL_SPI_TDR_TD(x) (x)
	#define ATMEL_SPI_TDR_PCS(x) ((x) << 16)
	#define ATMEL_SPI_TDR_LASTXFER BIT(24)

	/* Bits in SR/IER/IDR/IMR */
	#define ATMEL_SPI_SR_RDRF BIT(0)
	#define ATMEL_SPI_SR_TDRE BIT(1)
	#define ATMEL_SPI_SR_MODF BIT(2)
	#define ATMEL_SPI_SR_OVRES BIT(3)
	#define ATMEL_SPI_SR_ENDRX BIT(4)
	#define ATMEL_SPI_SR_ENDTX BIT(5)
	#define ATMEL_SPI_SR_RXBUFF BIT(6)
	#define ATMEL_SPI_SR_TXBUFE BIT(7)
	#define ATMEL_SPI_SR_NSSR BIT(8)
	#define ATMEL_SPI_SR_TXEMPTY BIT(9)
	#define ATMEL_SPI_SR_SPIENS BIT(16)

	/* Bits in CSRx */
	#define ATMEL_SPI_CSRx_CPOL BIT(0)
	#define ATMEL_SPI_CSRx_NCPHA BIT(1)
	#define ATMEL_SPI_CSRx_CSAAT BIT(3)
	#define ATMEL_SPI_CSRx_BITS(x) ((x) << 4)
	#define ATMEL_SPI_CSRx_SCBR(x) ((x) << 8)
	#define ATMEL_SPI_CSRx_SCBR_MAX GENMASK(7, 0)
	#define ATMEL_SPI_CSRx_DLYBS(x) ((x) << 16)
	#define ATMEL_SPI_CSRx_DLYBCT(x) ((x) << 24)

	/* Bits in VERSION */
	#define ATMEL_SPI_VERSION_REV(x) ((x) & 0xfff)
	#define ATMEL_SPI_VERSION_MFN(x) ((x) << 16)

	/* Constants for CSRx:BITS */
	#define ATMEL_SPI_BITS_8 0
	#define ATMEL_SPI_BITS_9 1
	#define ATMEL_SPI_BITS_10 2
	#define ATMEL_SPI_BITS_11 3
	#define ATMEL_SPI_BITS_12 4
	#define ATMEL_SPI_BITS_13 5
	#define ATMEL_SPI_BITS_14 6
	#define ATMEL_SPI_BITS_15 7
	#define ATMEL_SPI_BITS_16 8

	#define MAX_CS_COUNT 4

	/* Register access macros */
	#define spi_readl(as, reg) \
	readl(as->regs + ATMEL_SPI_##reg)
	#define spi_writel(as, reg, value) \
	writel(value, as->regs + ATMEL_SPI_##reg)

	struct atmel_spi_plat {
	struct at91_spi *regs;
	};

	struct atmel_spi_priv {
	unsigned int freq; /* Default frequency */
	unsigned int mode;
	ulong bus_clk_rate;
	#if CONFIG_IS_ENABLED(DM_GPIO)
	struct gpio_desc cs_gpios[MAX_CS_COUNT];
	#endif
	};

	static int atmel_spi_claim_bus(struct udevice *dev)
	{
	struct udevice *bus = dev_get_parent(dev);
	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
	struct atmel_spi_priv *priv = dev_get_priv(bus);
	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
	struct at91_spi *reg_base = bus_plat->regs;
	u32 cs = slave_plat->cs;
	u32 freq = priv->freq;
	u32 scbr, csrx, mode;

	scbr = (priv->bus_clk_rate + freq - 1) / freq;
	if (scbr > ATMEL_SPI_CSRx_SCBR_MAX)
	return -EINVAL;

	if (scbr < 1)
	scbr = 1;

	csrx = ATMEL_SPI_CSRx_SCBR(scbr);
	csrx \|= ATMEL_SPI_CSRx_BITS(ATMEL_SPI_BITS_8);

	if (!(priv->mode & SPI_CPHA))
	csrx \|= ATMEL_SPI_CSRx_NCPHA;
	if (priv->mode & SPI_CPOL)
	csrx \|= ATMEL_SPI_CSRx_CPOL;

	writel(csrx, &reg_base->csr[cs]);

	mode = ATMEL_SPI_MR_MSTR \|
	ATMEL_SPI_MR_MODFDIS \|
	ATMEL_SPI_MR_WDRBT \|
	ATMEL_SPI_MR_PCS(~(1 << cs));

	writel(mode, &reg_base->mr);

	writel(ATMEL_SPI_CR_SPIEN, &reg_base->cr);

	return 0;
	}

	static int atmel_spi_release_bus(struct udevice *dev)
	{
	struct udevice *bus = dev_get_parent(dev);
	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);

	writel(ATMEL_SPI_CR_SPIDIS, &bus_plat->regs->cr);

	return 0;
	}

	static void atmel_spi_cs_activate(struct udevice *dev)
	{
	#if CONFIG_IS_ENABLED(DM_GPIO)
	struct udevice *bus = dev_get_parent(dev);
	struct atmel_spi_priv *priv = dev_get_priv(bus);
	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
	u32 cs = slave_plat->cs;

	if (!dm_gpio_is_valid(&priv->cs_gpios[cs]))
	return;

	dm_gpio_set_value(&priv->cs_gpios[cs], 0);
	#endif
	}

	static void atmel_spi_cs_deactivate(struct udevice *dev)
	{
	#if CONFIG_IS_ENABLED(DM_GPIO)
	struct udevice *bus = dev_get_parent(dev);
	struct atmel_spi_priv *priv = dev_get_priv(bus);
	struct dm_spi_slave_plat *slave_plat = dev_get_parent_plat(dev);
	u32 cs = slave_plat->cs;

	if (!dm_gpio_is_valid(&priv->cs_gpios[cs]))
	return;

	dm_gpio_set_value(&priv->cs_gpios[cs], 1);
	#endif
	}

	static int atmel_spi_xfer(struct udevice *dev, unsigned int bitlen,
	const void dout, void din, unsigned long flags)
	{
	struct udevice *bus = dev_get_parent(dev);
	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
	struct at91_spi *reg_base = bus_plat->regs;

	u32 len_tx, len_rx, len;
	u32 status;
	const u8 *txp = dout;
	u8 *rxp = din;
	u8 value;

	if (bitlen == 0)
	goto out;

	/*
	* The controller can do non-multiple-of-8 bit
	* transfers, but this driver currently doesn't support it.
	*
	* It's also not clear how such transfers are supposed to be
	* represented as a stream of bytes...this is a limitation of
	* the current SPI interface.
	*/
	if (bitlen % 8) {
	/* Errors always terminate an ongoing transfer */
	flags \|= SPI_XFER_END;
	goto out;
	}

	len = bitlen / 8;

	/*
	* The controller can do automatic CS control, but it is
	* somewhat quirky, and it doesn't really buy us much anyway
	* in the context of U-Boot.
	*/
	if (flags & SPI_XFER_BEGIN) {
	atmel_spi_cs_activate(dev);

	/*
	* sometimes the RDR is not empty when we get here,
	* in theory that should not happen, but it DOES happen.
	* Read it here to be on the safe side.
	* That also clears the OVRES flag. Required if the
	* following loop exits due to OVRES!
	*/
	readl(&reg_base->rdr);
	}

	for (len_tx = 0, len_rx = 0; len_rx < len; ) {
	status = readl(&reg_base->sr);

	if (status & ATMEL_SPI_SR_OVRES)
	return -1;

	if ((len_tx < len) && (status & ATMEL_SPI_SR_TDRE)) {
	if (txp)
	value = *txp++;
	else
	value = 0;
	writel(value, &reg_base->tdr);
	len_tx++;
	}

	if (status & ATMEL_SPI_SR_RDRF) {
	value = readl(&reg_base->rdr);
	if (rxp)
	*rxp++ = value;
	len_rx++;
	}
	}

	out:
	if (flags & SPI_XFER_END) {
	/*
	* Wait until the transfer is completely done before
	* we deactivate CS.
	*/
	wait_for_bit_le32(&reg_base->sr,
	ATMEL_SPI_SR_TXEMPTY, true, 1000, false);

	atmel_spi_cs_deactivate(dev);
	}

	return 0;
	}

	static int atmel_spi_set_speed(struct udevice *bus, uint speed)
	{
	struct atmel_spi_priv *priv = dev_get_priv(bus);

	priv->freq = speed;

	return 0;
	}

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

	priv->mode = mode;

	return 0;
	}

	static const struct dm_spi_ops atmel_spi_ops = {
	.claim_bus = atmel_spi_claim_bus,
	.release_bus = atmel_spi_release_bus,
	.xfer = atmel_spi_xfer,
	.set_speed = atmel_spi_set_speed,
	.set_mode = atmel_spi_set_mode,
	/*
	* cs_info is not needed, since we require all chip selects to be
	* in the device tree explicitly
	*/
	};

	static int atmel_spi_enable_clk(struct udevice *bus)
	{
	struct atmel_spi_priv *priv = dev_get_priv(bus);
	struct clk clk;
	ulong clk_rate;
	int ret;

	ret = clk_get_by_index(bus, 0, &clk);
	if (ret)
	return -EINVAL;

	ret = clk_enable(&clk);
	if (ret)
	return ret;

	clk_rate = clk_get_rate(&clk);
	if (!clk_rate)
	return -EINVAL;

	priv->bus_clk_rate = clk_rate;

	return 0;
	}

	static int atmel_spi_probe(struct udevice *bus)
	{
	struct atmel_spi_plat *bus_plat = dev_get_plat(bus);
	int ret;

	ret = atmel_spi_enable_clk(bus);
	if (ret)
	return ret;

	bus_plat->regs = dev_read_addr_ptr(bus);

	#if CONFIG_IS_ENABLED(DM_GPIO)
	struct atmel_spi_priv *priv = dev_get_priv(bus);
	int i;

	ret = gpio_request_list_by_name(bus, "cs-gpios", priv->cs_gpios,
	ARRAY_SIZE(priv->cs_gpios), 0);
	if (ret < 0) {
	pr_err("Can't get %s gpios! Error: %d", bus->name, ret);
	return ret;
	}

	for(i = 0; i < ARRAY_SIZE(priv->cs_gpios); i++) {
	if (!dm_gpio_is_valid(&priv->cs_gpios[i]))
	continue;

	dm_gpio_set_dir_flags(&priv->cs_gpios[i],
	GPIOD_IS_OUT \| GPIOD_IS_OUT_ACTIVE);
	}
	#endif

	writel(ATMEL_SPI_CR_SWRST, &bus_plat->regs->cr);

	return 0;
	}

	static const struct udevice_id atmel_spi_ids[] = {
	{ .compatible = "atmel,at91rm9200-spi" },
	{ }
	};

	U_BOOT_DRIVER(atmel_spi) = {
	.name = "atmel_spi",
	.id = UCLASS_SPI,
	.of_match = atmel_spi_ids,
	.ops = &atmel_spi_ops,
	.plat_auto = sizeof(struct atmel_spi_plat),
	.priv_auto = sizeof(struct atmel_spi_priv),
	.probe = atmel_spi_probe,
	};