drivers/i2c/xilinx_xiic.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Xilinx AXI I2C driver
  *
  * Copyright (C) 2018 Marek Vasut <marex@denx.de>
  *
  * Based on Linux 4.14.y i2c-xiic.c
  * Copyright (c) 2002-2007 Xilinx Inc.
  * Copyright (c) 2009-2010 Intel Corporation
  */

 #include <clk.h>
 #include <dm.h>
 #include <i2c.h>
 #include <wait_bit.h>
 #include <asm/io.h>
 #include <dm/device_compat.h>

 struct xilinx_xiic_priv {
 	void __iomem		*base;
 	struct clk		clk;
 };

 #define XIIC_MSB_OFFSET 0
 #define XIIC_REG_OFFSET (0x100+XIIC_MSB_OFFSET)

 /*
  * Register offsets in bytes from RegisterBase. Three is added to the
  * base offset to access LSB (IBM style) of the word
  */
 #define XIIC_CR_REG_OFFSET   (0x00+XIIC_REG_OFFSET)	/* Control Register   */
 #define XIIC_SR_REG_OFFSET   (0x04+XIIC_REG_OFFSET)	/* Status Register    */
 #define XIIC_DTR_REG_OFFSET  (0x08+XIIC_REG_OFFSET)	/* Data Tx Register   */
 #define XIIC_DRR_REG_OFFSET  (0x0C+XIIC_REG_OFFSET)	/* Data Rx Register   */
 #define XIIC_ADR_REG_OFFSET  (0x10+XIIC_REG_OFFSET)	/* Address Register   */
 #define XIIC_TFO_REG_OFFSET  (0x14+XIIC_REG_OFFSET)	/* Tx FIFO Occupancy  */
 #define XIIC_RFO_REG_OFFSET  (0x18+XIIC_REG_OFFSET)	/* Rx FIFO Occupancy  */
 #define XIIC_TBA_REG_OFFSET  (0x1C+XIIC_REG_OFFSET)	/* 10 Bit Address reg */
 #define XIIC_RFD_REG_OFFSET  (0x20+XIIC_REG_OFFSET)	/* Rx FIFO Depth reg  */
 #define XIIC_GPO_REG_OFFSET  (0x24+XIIC_REG_OFFSET)	/* Output Register    */

 /* Control Register masks */
 #define XIIC_CR_ENABLE_DEVICE_MASK        0x01	/* Device enable = 1      */
 #define XIIC_CR_TX_FIFO_RESET_MASK        0x02	/* Transmit FIFO reset=1  */
 #define XIIC_CR_MSMS_MASK                 0x04	/* Master starts Txing=1  */
 #define XIIC_CR_DIR_IS_TX_MASK            0x08	/* Dir of tx. Txing=1     */
 #define XIIC_CR_NO_ACK_MASK               0x10	/* Tx Ack. NO ack = 1     */
 #define XIIC_CR_REPEATED_START_MASK       0x20	/* Repeated start = 1     */
 #define XIIC_CR_GENERAL_CALL_MASK         0x40	/* Gen Call enabled = 1   */

 /* Status Register masks */
 #define XIIC_SR_GEN_CALL_MASK             0x01	/* 1=a mstr issued a GC   */
 #define XIIC_SR_ADDR_AS_SLAVE_MASK        0x02	/* 1=when addr as slave   */
 #define XIIC_SR_BUS_BUSY_MASK             0x04	/* 1 = bus is busy        */
 #define XIIC_SR_MSTR_RDING_SLAVE_MASK     0x08	/* 1=Dir: mstr <-- slave  */
 #define XIIC_SR_TX_FIFO_FULL_MASK         0x10	/* 1 = Tx FIFO full       */
 #define XIIC_SR_RX_FIFO_FULL_MASK         0x20	/* 1 = Rx FIFO full       */
 #define XIIC_SR_RX_FIFO_EMPTY_MASK        0x40	/* 1 = Rx FIFO empty      */
 #define XIIC_SR_TX_FIFO_EMPTY_MASK        0x80	/* 1 = Tx FIFO empty      */

 /* Interrupt Status Register masks    Interrupt occurs when...       */
 #define XIIC_INTR_ARB_LOST_MASK           0x01	/* 1 = arbitration lost   */
 #define XIIC_INTR_TX_ERROR_MASK           0x02	/* 1=Tx error/msg complete */
 #define XIIC_INTR_TX_EMPTY_MASK           0x04	/* 1 = Tx FIFO/reg empty  */
 #define XIIC_INTR_RX_FULL_MASK            0x08	/* 1=Rx FIFO/reg=OCY level */
 #define XIIC_INTR_BNB_MASK                0x10	/* 1 = Bus not busy       */
 #define XIIC_INTR_AAS_MASK                0x20	/* 1 = when addr as slave */
 #define XIIC_INTR_NAAS_MASK               0x40	/* 1 = not addr as slave  */
 #define XIIC_INTR_TX_HALF_MASK            0x80	/* 1 = TX FIFO half empty */

 /* The following constants specify the depth of the FIFOs */
 #define IIC_RX_FIFO_DEPTH         16	/* Rx fifo capacity               */
 #define IIC_TX_FIFO_DEPTH         16	/* Tx fifo capacity               */

 /*
  * Tx Fifo upper bit masks.
  */
 #define XIIC_TX_DYN_START_MASK            0x0100 /* 1 = Set dynamic start */
 #define XIIC_TX_DYN_STOP_MASK             0x0200 /* 1 = Set dynamic stop */

 /*
  * The following constants define the register offsets for the Interrupt
  * registers. There are some holes in the memory map for reserved addresses
  * to allow other registers to be added and still match the memory map of the
  * interrupt controller registers
  */
 #define XIIC_DGIER_OFFSET    0x1C /* Device Global Interrupt Enable Register */
 #define XIIC_IISR_OFFSET     0x20 /* Interrupt Status Register */
 #define XIIC_IIER_OFFSET     0x28 /* Interrupt Enable Register */
 #define XIIC_RESETR_OFFSET   0x40 /* Reset Register */

 #define XIIC_RESET_MASK             0xAUL

 static u8 i2c_8bit_addr_from_flags(uint addr, u16 flags)
 {
 	return (addr << 1) | (flags & I2C_M_RD ? 1 : 0);
 }

 static void xiic_irq_clr(struct xilinx_xiic_priv *priv, u32 mask)
 {
 	u32 isr = readl(priv->base + XIIC_IISR_OFFSET);

 	writel(isr & mask, priv->base + XIIC_IISR_OFFSET);
 }

 static int xiic_read_rx(struct xilinx_xiic_priv *priv,
 			struct i2c_msg *msg, int nmsgs)
 {
 	u8 bytes_in_fifo;
 	u32 pos = 0;
 	int i, ret;

 	while (pos < msg->len) {
 		ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
 				     XIIC_SR_RX_FIFO_EMPTY_MASK, false,
 				     1000, true);
 		if (ret)
 			return ret;

 		bytes_in_fifo = readb(priv->base + XIIC_RFO_REG_OFFSET) + 1;

 		if (bytes_in_fifo > msg->len)
 			bytes_in_fifo = msg->len;

 		for (i = 0; i < bytes_in_fifo; i++) {
 			msg->buf[pos++] = readb(priv->base +
 						XIIC_DRR_REG_OFFSET);
 		}
 	}

 	return 0;
 }

 static int xiic_tx_fifo_space(struct xilinx_xiic_priv *priv)
 {
 	/* return the actual space left in the FIFO */
 	return IIC_TX_FIFO_DEPTH - readb(priv->base + XIIC_TFO_REG_OFFSET) - 1;
 }

 static void xiic_fill_tx_fifo(struct xilinx_xiic_priv *priv,
 			      struct i2c_msg *msg, int nmsgs)
 {
 	u8 fifo_space = xiic_tx_fifo_space(priv);
 	int len = msg->len;
 	u32 pos = 0;

 	len = (len > fifo_space) ? fifo_space : len;

 	while (len--) {
 		u16 data = msg->buf[pos++];

 		if ((msg->len - pos == 0) && nmsgs == 1) {
 			/* last message in transfer -> STOP */
 			data |= XIIC_TX_DYN_STOP_MASK;
 		}
 		writew(data, priv->base + XIIC_DTR_REG_OFFSET);
 	}
 }

 static void xilinx_xiic_set_addr(struct udevice *dev, u8 addr,
 				 u16 flags, u32 len, u32 nmsgs)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);

 	xiic_irq_clr(priv, XIIC_INTR_TX_ERROR_MASK);

 	if (!(flags & I2C_M_NOSTART)) {
 		/* write the address */
 		u16 data = i2c_8bit_addr_from_flags(addr, flags) |
 			XIIC_TX_DYN_START_MASK;
 		if (nmsgs == 1 && len == 0)
 			/* no data and last message -> add STOP */
 			data |= XIIC_TX_DYN_STOP_MASK;

 		writew(data, priv->base + XIIC_DTR_REG_OFFSET);
 	}
 }

 static int xilinx_xiic_read_common(struct udevice *dev, struct i2c_msg *msg,
 				   u32 nmsgs)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
 	u8 rx_watermark;

 	/* Clear and enable Rx full interrupt. */
 	xiic_irq_clr(priv, XIIC_INTR_RX_FULL_MASK | XIIC_INTR_TX_ERROR_MASK);

 	/* we want to get all but last byte, because the TX_ERROR IRQ is used
 	 * to inidicate error ACK on the address, and negative ack on the last
 	 * received byte, so to not mix them receive all but last.
 	 * In the case where there is only one byte to receive
 	 * we can check if ERROR and RX full is set at the same time
 	 */
 	rx_watermark = msg->len;
 	if (rx_watermark > IIC_RX_FIFO_DEPTH)
 		rx_watermark = IIC_RX_FIFO_DEPTH;

 	writeb(rx_watermark - 1, priv->base + XIIC_RFD_REG_OFFSET);

 	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);

 	xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);

 	writew((msg->len & 0xff) | ((nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0),
 	       priv->base + XIIC_DTR_REG_OFFSET);

 	if (nmsgs == 1)
 		/* very last, enable bus not busy as well */
 		xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);

 	return xiic_read_rx(priv, msg, nmsgs);
 }

 static int xilinx_xiic_write_common(struct udevice *dev, struct i2c_msg *msg,
 				    int nmsgs)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
 	int ret;

 	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);
 	xiic_fill_tx_fifo(priv, msg, nmsgs);

 	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
 			     XIIC_SR_TX_FIFO_EMPTY_MASK, false, 1000, true);
 	if (ret)
 		return ret;

 	/* Clear any pending Tx empty, Tx Error and then enable them. */
 	xiic_irq_clr(priv, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
 			   XIIC_INTR_BNB_MASK);

 	return 0;
 }

 static void xiic_clear_rx_fifo(struct xilinx_xiic_priv *priv)
 {
 	u8 sr;

 	for (sr = readb(priv->base + XIIC_SR_REG_OFFSET);
 		!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
 		sr = readb(priv->base + XIIC_SR_REG_OFFSET))
 		readb(priv->base + XIIC_DRR_REG_OFFSET);
 }

 static void xiic_reinit(struct xilinx_xiic_priv *priv)
 {
 	writel(XIIC_RESET_MASK, priv->base + XIIC_RESETR_OFFSET);

 	/* Set receive Fifo depth to maximum (zero based). */
 	writeb(IIC_RX_FIFO_DEPTH - 1, priv->base + XIIC_RFD_REG_OFFSET);

 	/* Reset Tx Fifo. */
 	writeb(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);

 	/* Enable IIC Device, remove Tx Fifo reset & disable general call. */
 	writeb(XIIC_CR_ENABLE_DEVICE_MASK, priv->base + XIIC_CR_REG_OFFSET);

 	/* make sure RX fifo is empty */
 	xiic_clear_rx_fifo(priv);

 	/* Disable interrupts */
 	writel(0, priv->base + XIIC_DGIER_OFFSET);

 	xiic_irq_clr(priv, XIIC_INTR_ARB_LOST_MASK);
 }

 static int xilinx_xiic_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
 	int ret = 0;

 	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
 			     XIIC_SR_BUS_BUSY_MASK, false, 1000, true);

 	if (ret == -ETIMEDOUT)
 		dev_err(dev, "timeout waiting for bus not busy condition\n");

 	if (ret)
 		return ret;

 	xiic_reinit(priv);

 	for (; nmsgs > 0; nmsgs--, msg++) {
 		if (msg->flags & I2C_M_RD)
 			ret = xilinx_xiic_read_common(dev, msg, nmsgs);
 		else
 			ret = xilinx_xiic_write_common(dev, msg, nmsgs);

 		if (ret)
 			return -EREMOTEIO;
 	}

 	return ret;
 }

 static int xilinx_xiic_probe_chip(struct udevice *dev, uint addr, uint flags)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
 	u32 reg;
 	int ret;

 	xiic_reinit(priv);

 	xilinx_xiic_set_addr(dev, addr, 0, 0, 1);
 	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
 			     XIIC_SR_BUS_BUSY_MASK, false, 1000, true);
 	if (ret)
 		return ret;

 	reg = readl(priv->base + XIIC_IISR_OFFSET);
 	if (reg & XIIC_INTR_TX_ERROR_MASK)
 		return -ENODEV;

 	return 0;
 }

 static int xilinx_xiic_set_speed(struct udevice *dev, uint speed)
 {
 	return 0;
 }

 static int xilinx_xiic_probe(struct udevice *dev)
 {
 	struct xilinx_xiic_priv *priv = dev_get_priv(dev);

 	priv->base = dev_read_addr_ptr(dev);

 	writel(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);
 	xiic_reinit(priv);

 	return 0;
 }

 static const struct dm_i2c_ops xilinx_xiic_ops = {
 	.xfer		= xilinx_xiic_xfer,
 	.probe_chip	= xilinx_xiic_probe_chip,
 	.set_bus_speed	= xilinx_xiic_set_speed,
 };

 static const struct udevice_id xilinx_xiic_ids[] = {
 	{ .compatible = "xlnx,xps-iic-2.00.a" },
 	{ }
 };

 U_BOOT_DRIVER(xilinx_xiic) = {
 	.name		= "xilinx_axi_i2c",
 	.id		= UCLASS_I2C,
 	.of_match	= xilinx_xiic_ids,
 	.probe		= xilinx_xiic_probe,
 	.priv_auto	= sizeof(struct xilinx_xiic_priv),
 	.ops		= &xilinx_xiic_ops,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Xilinx AXI I2C driver
	*
	* Copyright (C) 2018 Marek Vasut <marex@denx.de>
	*
	* Based on Linux 4.14.y i2c-xiic.c
	* Copyright (c) 2002-2007 Xilinx Inc.
	* Copyright (c) 2009-2010 Intel Corporation
	*/

	#include <clk.h>
	#include <dm.h>
	#include <i2c.h>
	#include <wait_bit.h>
	#include <asm/io.h>
	#include <dm/device_compat.h>

	struct xilinx_xiic_priv {
	void __iomem *base;
	struct clk clk;
	};

	#define XIIC_MSB_OFFSET 0
	#define XIIC_REG_OFFSET (0x100+XIIC_MSB_OFFSET)

	/*
	* Register offsets in bytes from RegisterBase. Three is added to the
	* base offset to access LSB (IBM style) of the word
	*/
	#define XIIC_CR_REG_OFFSET (0x00+XIIC_REG_OFFSET) /* Control Register */
	#define XIIC_SR_REG_OFFSET (0x04+XIIC_REG_OFFSET) /* Status Register */
	#define XIIC_DTR_REG_OFFSET (0x08+XIIC_REG_OFFSET) /* Data Tx Register */
	#define XIIC_DRR_REG_OFFSET (0x0C+XIIC_REG_OFFSET) /* Data Rx Register */
	#define XIIC_ADR_REG_OFFSET (0x10+XIIC_REG_OFFSET) /* Address Register */
	#define XIIC_TFO_REG_OFFSET (0x14+XIIC_REG_OFFSET) /* Tx FIFO Occupancy */
	#define XIIC_RFO_REG_OFFSET (0x18+XIIC_REG_OFFSET) /* Rx FIFO Occupancy */
	#define XIIC_TBA_REG_OFFSET (0x1C+XIIC_REG_OFFSET) /* 10 Bit Address reg */
	#define XIIC_RFD_REG_OFFSET (0x20+XIIC_REG_OFFSET) /* Rx FIFO Depth reg */
	#define XIIC_GPO_REG_OFFSET (0x24+XIIC_REG_OFFSET) /* Output Register */

	/* Control Register masks */
	#define XIIC_CR_ENABLE_DEVICE_MASK 0x01 /* Device enable = 1 */
	#define XIIC_CR_TX_FIFO_RESET_MASK 0x02 /* Transmit FIFO reset=1 */
	#define XIIC_CR_MSMS_MASK 0x04 /* Master starts Txing=1 */
	#define XIIC_CR_DIR_IS_TX_MASK 0x08 /* Dir of tx. Txing=1 */
	#define XIIC_CR_NO_ACK_MASK 0x10 /* Tx Ack. NO ack = 1 */
	#define XIIC_CR_REPEATED_START_MASK 0x20 /* Repeated start = 1 */
	#define XIIC_CR_GENERAL_CALL_MASK 0x40 /* Gen Call enabled = 1 */

	/* Status Register masks */
	#define XIIC_SR_GEN_CALL_MASK 0x01 /* 1=a mstr issued a GC */
	#define XIIC_SR_ADDR_AS_SLAVE_MASK 0x02 /* 1=when addr as slave */
	#define XIIC_SR_BUS_BUSY_MASK 0x04 /* 1 = bus is busy */
	#define XIIC_SR_MSTR_RDING_SLAVE_MASK 0x08 /* 1=Dir: mstr <-- slave */
	#define XIIC_SR_TX_FIFO_FULL_MASK 0x10 /* 1 = Tx FIFO full */
	#define XIIC_SR_RX_FIFO_FULL_MASK 0x20 /* 1 = Rx FIFO full */
	#define XIIC_SR_RX_FIFO_EMPTY_MASK 0x40 /* 1 = Rx FIFO empty */
	#define XIIC_SR_TX_FIFO_EMPTY_MASK 0x80 /* 1 = Tx FIFO empty */

	/* Interrupt Status Register masks Interrupt occurs when... */
	#define XIIC_INTR_ARB_LOST_MASK 0x01 /* 1 = arbitration lost */
	#define XIIC_INTR_TX_ERROR_MASK 0x02 /* 1=Tx error/msg complete */
	#define XIIC_INTR_TX_EMPTY_MASK 0x04 /* 1 = Tx FIFO/reg empty */
	#define XIIC_INTR_RX_FULL_MASK 0x08 /* 1=Rx FIFO/reg=OCY level */
	#define XIIC_INTR_BNB_MASK 0x10 /* 1 = Bus not busy */
	#define XIIC_INTR_AAS_MASK 0x20 /* 1 = when addr as slave */
	#define XIIC_INTR_NAAS_MASK 0x40 /* 1 = not addr as slave */
	#define XIIC_INTR_TX_HALF_MASK 0x80 /* 1 = TX FIFO half empty */

	/* The following constants specify the depth of the FIFOs */
	#define IIC_RX_FIFO_DEPTH 16 /* Rx fifo capacity */
	#define IIC_TX_FIFO_DEPTH 16 /* Tx fifo capacity */

	/*
	* Tx Fifo upper bit masks.
	*/
	#define XIIC_TX_DYN_START_MASK 0x0100 /* 1 = Set dynamic start */
	#define XIIC_TX_DYN_STOP_MASK 0x0200 /* 1 = Set dynamic stop */

	/*
	* The following constants define the register offsets for the Interrupt
	* registers. There are some holes in the memory map for reserved addresses
	* to allow other registers to be added and still match the memory map of the
	* interrupt controller registers
	*/
	#define XIIC_DGIER_OFFSET 0x1C /* Device Global Interrupt Enable Register */
	#define XIIC_IISR_OFFSET 0x20 /* Interrupt Status Register */
	#define XIIC_IIER_OFFSET 0x28 /* Interrupt Enable Register */
	#define XIIC_RESETR_OFFSET 0x40 /* Reset Register */

	#define XIIC_RESET_MASK 0xAUL

	static u8 i2c_8bit_addr_from_flags(uint addr, u16 flags)
	{
	return (addr << 1) \| (flags & I2C_M_RD ? 1 : 0);
	}

	static void xiic_irq_clr(struct xilinx_xiic_priv *priv, u32 mask)
	{
	u32 isr = readl(priv->base + XIIC_IISR_OFFSET);

	writel(isr & mask, priv->base + XIIC_IISR_OFFSET);
	}

	static int xiic_read_rx(struct xilinx_xiic_priv *priv,
	struct i2c_msg *msg, int nmsgs)
	{
	u8 bytes_in_fifo;
	u32 pos = 0;
	int i, ret;

	while (pos < msg->len) {
	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
	XIIC_SR_RX_FIFO_EMPTY_MASK, false,
	1000, true);
	if (ret)
	return ret;

	bytes_in_fifo = readb(priv->base + XIIC_RFO_REG_OFFSET) + 1;

	if (bytes_in_fifo > msg->len)
	bytes_in_fifo = msg->len;

	for (i = 0; i < bytes_in_fifo; i++) {
	msg->buf[pos++] = readb(priv->base +
	XIIC_DRR_REG_OFFSET);
	}
	}

	return 0;
	}

	static int xiic_tx_fifo_space(struct xilinx_xiic_priv *priv)
	{
	/* return the actual space left in the FIFO */
	return IIC_TX_FIFO_DEPTH - readb(priv->base + XIIC_TFO_REG_OFFSET) - 1;
	}

	static void xiic_fill_tx_fifo(struct xilinx_xiic_priv *priv,
	struct i2c_msg *msg, int nmsgs)
	{
	u8 fifo_space = xiic_tx_fifo_space(priv);
	int len = msg->len;
	u32 pos = 0;

	len = (len > fifo_space) ? fifo_space : len;

	while (len--) {
	u16 data = msg->buf[pos++];

	if ((msg->len - pos == 0) && nmsgs == 1) {
	/* last message in transfer -> STOP */
	data \|= XIIC_TX_DYN_STOP_MASK;
	}
	writew(data, priv->base + XIIC_DTR_REG_OFFSET);
	}
	}

	static void xilinx_xiic_set_addr(struct udevice *dev, u8 addr,
	u16 flags, u32 len, u32 nmsgs)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);

	xiic_irq_clr(priv, XIIC_INTR_TX_ERROR_MASK);

	if (!(flags & I2C_M_NOSTART)) {
	/* write the address */
	u16 data = i2c_8bit_addr_from_flags(addr, flags) \|
	XIIC_TX_DYN_START_MASK;
	if (nmsgs == 1 && len == 0)
	/* no data and last message -> add STOP */
	data \|= XIIC_TX_DYN_STOP_MASK;

	writew(data, priv->base + XIIC_DTR_REG_OFFSET);
	}
	}

	static int xilinx_xiic_read_common(struct udevice dev, struct i2c_msg msg,
	u32 nmsgs)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
	u8 rx_watermark;

	/* Clear and enable Rx full interrupt. */
	xiic_irq_clr(priv, XIIC_INTR_RX_FULL_MASK \| XIIC_INTR_TX_ERROR_MASK);

	/* we want to get all but last byte, because the TX_ERROR IRQ is used
	* to inidicate error ACK on the address, and negative ack on the last
	* received byte, so to not mix them receive all but last.
	* In the case where there is only one byte to receive
	* we can check if ERROR and RX full is set at the same time
	*/
	rx_watermark = msg->len;
	if (rx_watermark > IIC_RX_FIFO_DEPTH)
	rx_watermark = IIC_RX_FIFO_DEPTH;

	writeb(rx_watermark - 1, priv->base + XIIC_RFD_REG_OFFSET);

	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);

	xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);

	writew((msg->len & 0xff) \| ((nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0),
	priv->base + XIIC_DTR_REG_OFFSET);

	if (nmsgs == 1)
	/* very last, enable bus not busy as well */
	xiic_irq_clr(priv, XIIC_INTR_BNB_MASK);

	return xiic_read_rx(priv, msg, nmsgs);
	}

	static int xilinx_xiic_write_common(struct udevice dev, struct i2c_msg msg,
	int nmsgs)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
	int ret;

	xilinx_xiic_set_addr(dev, msg->addr, msg->flags, msg->len, nmsgs);
	xiic_fill_tx_fifo(priv, msg, nmsgs);

	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
	XIIC_SR_TX_FIFO_EMPTY_MASK, false, 1000, true);
	if (ret)
	return ret;

	/* Clear any pending Tx empty, Tx Error and then enable them. */
	xiic_irq_clr(priv, XIIC_INTR_TX_EMPTY_MASK \| XIIC_INTR_TX_ERROR_MASK \|
	XIIC_INTR_BNB_MASK);

	return 0;
	}

	static void xiic_clear_rx_fifo(struct xilinx_xiic_priv *priv)
	{
	u8 sr;

	for (sr = readb(priv->base + XIIC_SR_REG_OFFSET);
	!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
	sr = readb(priv->base + XIIC_SR_REG_OFFSET))
	readb(priv->base + XIIC_DRR_REG_OFFSET);
	}

	static void xiic_reinit(struct xilinx_xiic_priv *priv)
	{
	writel(XIIC_RESET_MASK, priv->base + XIIC_RESETR_OFFSET);

	/* Set receive Fifo depth to maximum (zero based). */
	writeb(IIC_RX_FIFO_DEPTH - 1, priv->base + XIIC_RFD_REG_OFFSET);

	/* Reset Tx Fifo. */
	writeb(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);

	/* Enable IIC Device, remove Tx Fifo reset & disable general call. */
	writeb(XIIC_CR_ENABLE_DEVICE_MASK, priv->base + XIIC_CR_REG_OFFSET);

	/* make sure RX fifo is empty */
	xiic_clear_rx_fifo(priv);

	/* Disable interrupts */
	writel(0, priv->base + XIIC_DGIER_OFFSET);

	xiic_irq_clr(priv, XIIC_INTR_ARB_LOST_MASK);
	}

	static int xilinx_xiic_xfer(struct udevice dev, struct i2c_msg msg, int nmsgs)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
	int ret = 0;

	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
	XIIC_SR_BUS_BUSY_MASK, false, 1000, true);

	if (ret == -ETIMEDOUT)
	dev_err(dev, "timeout waiting for bus not busy condition\n");

	if (ret)
	return ret;

	xiic_reinit(priv);

	for (; nmsgs > 0; nmsgs--, msg++) {
	if (msg->flags & I2C_M_RD)
	ret = xilinx_xiic_read_common(dev, msg, nmsgs);
	else
	ret = xilinx_xiic_write_common(dev, msg, nmsgs);

	if (ret)
	return -EREMOTEIO;
	}

	return ret;
	}

	static int xilinx_xiic_probe_chip(struct udevice *dev, uint addr, uint flags)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);
	u32 reg;
	int ret;

	xiic_reinit(priv);

	xilinx_xiic_set_addr(dev, addr, 0, 0, 1);
	ret = wait_for_bit_8(priv->base + XIIC_SR_REG_OFFSET,
	XIIC_SR_BUS_BUSY_MASK, false, 1000, true);
	if (ret)
	return ret;

	reg = readl(priv->base + XIIC_IISR_OFFSET);
	if (reg & XIIC_INTR_TX_ERROR_MASK)
	return -ENODEV;

	return 0;
	}

	static int xilinx_xiic_set_speed(struct udevice *dev, uint speed)
	{
	return 0;
	}

	static int xilinx_xiic_probe(struct udevice *dev)
	{
	struct xilinx_xiic_priv *priv = dev_get_priv(dev);

	priv->base = dev_read_addr_ptr(dev);

	writel(XIIC_CR_TX_FIFO_RESET_MASK, priv->base + XIIC_CR_REG_OFFSET);
	xiic_reinit(priv);

	return 0;
	}

	static const struct dm_i2c_ops xilinx_xiic_ops = {
	.xfer = xilinx_xiic_xfer,
	.probe_chip = xilinx_xiic_probe_chip,
	.set_bus_speed = xilinx_xiic_set_speed,
	};

	static const struct udevice_id xilinx_xiic_ids[] = {
	{ .compatible = "xlnx,xps-iic-2.00.a" },
	{ }
	};

	U_BOOT_DRIVER(xilinx_xiic) = {
	.name = "xilinx_axi_i2c",
	.id = UCLASS_I2C,
	.of_match = xilinx_xiic_ids,
	.probe = xilinx_xiic_probe,
	.priv_auto = sizeof(struct xilinx_xiic_priv),
	.ops = &xilinx_xiic_ops,
	};