Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 930 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
new file mode 100644
index 000000000..b27bfc776
--- /dev/null
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -0,0 +1,930 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * i2c-xiic.c
+ * Copyright (c) 2002-2007 Xilinx Inc.
+ * Copyright (c) 2009-2010 Intel Corporation
+ *
+ * This code was implemented by Mocean Laboratories AB when porting linux
+ * to the automotive development board Russellville. The copyright holder
+ * as seen in the header is Intel corporation.
+ * Mocean Laboratories forked off the GNU/Linux platform work into a
+ * separate company called Pelagicore AB, which committed the code to the
+ * kernel.
+ */
+
+/* Supports:
+ * Xilinx IIC
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/completion.h>
+#include <linux/platform_data/i2c-xiic.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+
+#define DRIVER_NAME "xiic-i2c"
+
+enum xilinx_i2c_state {
+	STATE_DONE,
+	STATE_ERROR,
+	STATE_START
+};
+
+enum xiic_endian {
+	LITTLE,
+	BIG
+};
+
+/**
+ * struct xiic_i2c - Internal representation of the XIIC I2C bus
+ * @dev: Pointer to device structure
+ * @base: Memory base of the HW registers
+ * @completion:	Completion for callers
+ * @adap: Kernel adapter representation
+ * @tx_msg: Messages from above to be sent
+ * @lock: Mutual exclusion
+ * @tx_pos: Current pos in TX message
+ * @nmsgs: Number of messages in tx_msg
+ * @rx_msg: Current RX message
+ * @rx_pos: Position within current RX message
+ * @endianness: big/little-endian byte order
+ * @clk: Pointer to AXI4-lite input clock
+ * @state: See STATE_
+ * @singlemaster: Indicates bus is single master
+ */
+struct xiic_i2c {
+	struct device *dev;
+	void __iomem *base;
+	struct completion completion;
+	struct i2c_adapter adap;
+	struct i2c_msg *tx_msg;
+	struct mutex lock;
+	unsigned int tx_pos;
+	unsigned int nmsgs;
+	struct i2c_msg *rx_msg;
+	int rx_pos;
+	enum xiic_endian endianness;
+	struct clk *clk;
+	enum xilinx_i2c_state state;
+	bool singlemaster;
+};
+
+#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               */
+
+/* The following constants specify groups of interrupts that are typically
+ * enabled or disables at the same time
+ */
+#define XIIC_TX_INTERRUPTS                           \
+(XIIC_INTR_TX_ERROR_MASK | XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)
+
+#define XIIC_TX_RX_INTERRUPTS (XIIC_INTR_RX_FULL_MASK | XIIC_TX_INTERRUPTS)
+
+/*
+ * 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
+
+#define XIIC_PM_TIMEOUT		1000	/* ms */
+/* timeout waiting for the controller to respond */
+#define XIIC_I2C_TIMEOUT	(msecs_to_jiffies(1000))
+/* timeout waiting for the controller finish transfers */
+#define XIIC_XFER_TIMEOUT	(msecs_to_jiffies(10000))
+
+/*
+ * The following constant is used for the device global interrupt enable
+ * register, to enable all interrupts for the device, this is the only bit
+ * in the register
+ */
+#define XIIC_GINTR_ENABLE_MASK      0x80000000UL
+
+#define xiic_tx_space(i2c) ((i2c)->tx_msg->len - (i2c)->tx_pos)
+#define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)
+
+static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num);
+static void __xiic_start_xfer(struct xiic_i2c *i2c);
+
+/*
+ * For the register read and write functions, a little-endian and big-endian
+ * version are necessary. Endianness is detected during the probe function.
+ * Only the least significant byte [doublet] of the register are ever
+ * accessed. This requires an offset of 3 [2] from the base address for
+ * big-endian systems.
+ */
+
+static inline void xiic_setreg8(struct xiic_i2c *i2c, int reg, u8 value)
+{
+	if (i2c->endianness == LITTLE)
+		iowrite8(value, i2c->base + reg);
+	else
+		iowrite8(value, i2c->base + reg + 3);
+}
+
+static inline u8 xiic_getreg8(struct xiic_i2c *i2c, int reg)
+{
+	u8 ret;
+
+	if (i2c->endianness == LITTLE)
+		ret = ioread8(i2c->base + reg);
+	else
+		ret = ioread8(i2c->base + reg + 3);
+	return ret;
+}
+
+static inline void xiic_setreg16(struct xiic_i2c *i2c, int reg, u16 value)
+{
+	if (i2c->endianness == LITTLE)
+		iowrite16(value, i2c->base + reg);
+	else
+		iowrite16be(value, i2c->base + reg + 2);
+}
+
+static inline void xiic_setreg32(struct xiic_i2c *i2c, int reg, int value)
+{
+	if (i2c->endianness == LITTLE)
+		iowrite32(value, i2c->base + reg);
+	else
+		iowrite32be(value, i2c->base + reg);
+}
+
+static inline int xiic_getreg32(struct xiic_i2c *i2c, int reg)
+{
+	u32 ret;
+
+	if (i2c->endianness == LITTLE)
+		ret = ioread32(i2c->base + reg);
+	else
+		ret = ioread32be(i2c->base + reg);
+	return ret;
+}
+
+static inline void xiic_irq_dis(struct xiic_i2c *i2c, u32 mask)
+{
+	u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
+
+	xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier & ~mask);
+}
+
+static inline void xiic_irq_en(struct xiic_i2c *i2c, u32 mask)
+{
+	u32 ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
+
+	xiic_setreg32(i2c, XIIC_IIER_OFFSET, ier | mask);
+}
+
+static inline void xiic_irq_clr(struct xiic_i2c *i2c, u32 mask)
+{
+	u32 isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
+
+	xiic_setreg32(i2c, XIIC_IISR_OFFSET, isr & mask);
+}
+
+static inline void xiic_irq_clr_en(struct xiic_i2c *i2c, u32 mask)
+{
+	xiic_irq_clr(i2c, mask);
+	xiic_irq_en(i2c, mask);
+}
+
+static int xiic_clear_rx_fifo(struct xiic_i2c *i2c)
+{
+	u8 sr;
+	unsigned long timeout;
+
+	timeout = jiffies + XIIC_I2C_TIMEOUT;
+	for (sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
+		!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
+		sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET)) {
+		xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
+		if (time_after(jiffies, timeout)) {
+			dev_err(i2c->dev, "Failed to clear rx fifo\n");
+			return -ETIMEDOUT;
+		}
+	}
+
+	return 0;
+}
+
+static int xiic_reinit(struct xiic_i2c *i2c)
+{
+	int ret;
+
+	xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);
+
+	/* Set receive Fifo depth to maximum (zero based). */
+	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, IIC_RX_FIFO_DEPTH - 1);
+
+	/* Reset Tx Fifo. */
+	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);
+
+	/* Enable IIC Device, remove Tx Fifo reset & disable general call. */
+	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_ENABLE_DEVICE_MASK);
+
+	/* make sure RX fifo is empty */
+	ret = xiic_clear_rx_fifo(i2c);
+	if (ret)
+		return ret;
+
+	/* Enable interrupts */
+	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+
+	xiic_irq_clr_en(i2c, XIIC_INTR_ARB_LOST_MASK);
+
+	return 0;
+}
+
+static void xiic_deinit(struct xiic_i2c *i2c)
+{
+	u8 cr;
+
+	xiic_setreg32(i2c, XIIC_RESETR_OFFSET, XIIC_RESET_MASK);
+
+	/* Disable IIC Device. */
+	cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
+	xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr & ~XIIC_CR_ENABLE_DEVICE_MASK);
+}
+
+static void xiic_read_rx(struct xiic_i2c *i2c)
+{
+	u8 bytes_in_fifo;
+	int i;
+
+	bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;
+
+	dev_dbg(i2c->adap.dev.parent,
+		"%s entry, bytes in fifo: %d, msg: %d, SR: 0x%x, CR: 0x%x\n",
+		__func__, bytes_in_fifo, xiic_rx_space(i2c),
+		xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
+		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+
+	if (bytes_in_fifo > xiic_rx_space(i2c))
+		bytes_in_fifo = xiic_rx_space(i2c);
+
+	for (i = 0; i < bytes_in_fifo; i++)
+		i2c->rx_msg->buf[i2c->rx_pos++] =
+			xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
+
+	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET,
+		(xiic_rx_space(i2c) > IIC_RX_FIFO_DEPTH) ?
+		IIC_RX_FIFO_DEPTH - 1 :  xiic_rx_space(i2c) - 1);
+}
+
+static int xiic_tx_fifo_space(struct xiic_i2c *i2c)
+{
+	/* return the actual space left in the FIFO */
+	return IIC_TX_FIFO_DEPTH - xiic_getreg8(i2c, XIIC_TFO_REG_OFFSET) - 1;
+}
+
+static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
+{
+	u8 fifo_space = xiic_tx_fifo_space(i2c);
+	int len = xiic_tx_space(i2c);
+
+	len = (len > fifo_space) ? fifo_space : len;
+
+	dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
+		__func__, len, fifo_space);
+
+	while (len--) {
+		u16 data = i2c->tx_msg->buf[i2c->tx_pos++];
+
+		if (!xiic_tx_space(i2c) && i2c->nmsgs == 1) {
+			/* last message in transfer -> STOP */
+			data |= XIIC_TX_DYN_STOP_MASK;
+			dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
+		}
+		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+	}
+}
+
+static void xiic_wakeup(struct xiic_i2c *i2c, enum xilinx_i2c_state code)
+{
+	i2c->tx_msg = NULL;
+	i2c->rx_msg = NULL;
+	i2c->nmsgs = 0;
+	i2c->state = code;
+	complete(&i2c->completion);
+}
+
+static irqreturn_t xiic_process(int irq, void *dev_id)
+{
+	struct xiic_i2c *i2c = dev_id;
+	u32 pend, isr, ier;
+	u32 clr = 0;
+	int xfer_more = 0;
+	int wakeup_req = 0;
+	enum xilinx_i2c_state wakeup_code = STATE_DONE;
+	int ret;
+
+	/* Get the interrupt Status from the IPIF. There is no clearing of
+	 * interrupts in the IPIF. Interrupts must be cleared at the source.
+	 * To find which interrupts are pending; AND interrupts pending with
+	 * interrupts masked.
+	 */
+	mutex_lock(&i2c->lock);
+	isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
+	ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
+	pend = isr & ier;
+
+	dev_dbg(i2c->adap.dev.parent, "%s: IER: 0x%x, ISR: 0x%x, pend: 0x%x\n",
+		__func__, ier, isr, pend);
+	dev_dbg(i2c->adap.dev.parent, "%s: SR: 0x%x, msg: %p, nmsgs: %d\n",
+		__func__, xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
+		i2c->tx_msg, i2c->nmsgs);
+
+
+	/* Service requesting interrupt */
+	if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
+	    ((pend & XIIC_INTR_TX_ERROR_MASK) &&
+	    !(pend & XIIC_INTR_RX_FULL_MASK))) {
+		/* bus arbritration lost, or...
+		 * Transmit error _OR_ RX completed
+		 * if this happens when RX_FULL is not set
+		 * this is probably a TX error
+		 */
+
+		dev_dbg(i2c->adap.dev.parent, "%s error\n", __func__);
+
+		/* dynamic mode seem to suffer from problems if we just flushes
+		 * fifos and the next message is a TX with len 0 (only addr)
+		 * reset the IP instead of just flush fifos
+		 */
+		ret = xiic_reinit(i2c);
+		if (ret < 0)
+			dev_dbg(i2c->adap.dev.parent, "reinit failed\n");
+
+		if (i2c->rx_msg) {
+			wakeup_req = 1;
+			wakeup_code = STATE_ERROR;
+		}
+		if (i2c->tx_msg) {
+			wakeup_req = 1;
+			wakeup_code = STATE_ERROR;
+		}
+		/* don't try to handle other events */
+		goto out;
+	}
+	if (pend & XIIC_INTR_RX_FULL_MASK) {
+		/* Receive register/FIFO is full */
+
+		clr |= XIIC_INTR_RX_FULL_MASK;
+		if (!i2c->rx_msg) {
+			dev_dbg(i2c->adap.dev.parent,
+				"%s unexpected RX IRQ\n", __func__);
+			xiic_clear_rx_fifo(i2c);
+			goto out;
+		}
+
+		xiic_read_rx(i2c);
+		if (xiic_rx_space(i2c) == 0) {
+			/* this is the last part of the message */
+			i2c->rx_msg = NULL;
+
+			/* also clear TX error if there (RX complete) */
+			clr |= (isr & XIIC_INTR_TX_ERROR_MASK);
+
+			dev_dbg(i2c->adap.dev.parent,
+				"%s end of message, nmsgs: %d\n",
+				__func__, i2c->nmsgs);
+
+			/* send next message if this wasn't the last,
+			 * otherwise the transfer will be finialise when
+			 * receiving the bus not busy interrupt
+			 */
+			if (i2c->nmsgs > 1) {
+				i2c->nmsgs--;
+				i2c->tx_msg++;
+				dev_dbg(i2c->adap.dev.parent,
+					"%s will start next...\n", __func__);
+				xfer_more = 1;
+			}
+		}
+	}
+	if (pend & (XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)) {
+		/* Transmit register/FIFO is empty or ½ empty */
+
+		clr |= (pend &
+			(XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK));
+
+		if (!i2c->tx_msg) {
+			dev_dbg(i2c->adap.dev.parent,
+				"%s unexpected TX IRQ\n", __func__);
+			goto out;
+		}
+
+		xiic_fill_tx_fifo(i2c);
+
+		/* current message sent and there is space in the fifo */
+		if (!xiic_tx_space(i2c) && xiic_tx_fifo_space(i2c) >= 2) {
+			dev_dbg(i2c->adap.dev.parent,
+				"%s end of message sent, nmsgs: %d\n",
+				__func__, i2c->nmsgs);
+			if (i2c->nmsgs > 1) {
+				i2c->nmsgs--;
+				i2c->tx_msg++;
+				xfer_more = 1;
+			} else {
+				xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
+
+				dev_dbg(i2c->adap.dev.parent,
+					"%s Got TX IRQ but no more to do...\n",
+					__func__);
+			}
+		} else if (!xiic_tx_space(i2c) && (i2c->nmsgs == 1))
+			/* current frame is sent and is last,
+			 * make sure to disable tx half
+			 */
+			xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
+	}
+
+	if (pend & XIIC_INTR_BNB_MASK) {
+		/* IIC bus has transitioned to not busy */
+		clr |= XIIC_INTR_BNB_MASK;
+
+		/* The bus is not busy, disable BusNotBusy interrupt */
+		xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);
+
+		if (!i2c->tx_msg)
+			goto out;
+
+		wakeup_req = 1;
+
+		if (i2c->nmsgs == 1 && !i2c->rx_msg &&
+		    xiic_tx_space(i2c) == 0)
+			wakeup_code = STATE_DONE;
+		else
+			wakeup_code = STATE_ERROR;
+	}
+
+out:
+	dev_dbg(i2c->adap.dev.parent, "%s clr: 0x%x\n", __func__, clr);
+
+	xiic_setreg32(i2c, XIIC_IISR_OFFSET, clr);
+	if (xfer_more)
+		__xiic_start_xfer(i2c);
+	if (wakeup_req)
+		xiic_wakeup(i2c, wakeup_code);
+
+	WARN_ON(xfer_more && wakeup_req);
+
+	mutex_unlock(&i2c->lock);
+	return IRQ_HANDLED;
+}
+
+static int xiic_bus_busy(struct xiic_i2c *i2c)
+{
+	u8 sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
+
+	return (sr & XIIC_SR_BUS_BUSY_MASK) ? -EBUSY : 0;
+}
+
+static int xiic_busy(struct xiic_i2c *i2c)
+{
+	int tries = 3;
+	int err;
+
+	if (i2c->tx_msg || i2c->rx_msg)
+		return -EBUSY;
+
+	/* In single master mode bus can only be busy, when in use by this
+	 * driver. If the register indicates bus being busy for some reason we
+	 * should ignore it, since bus will never be released and i2c will be
+	 * stuck forever.
+	 */
+	if (i2c->singlemaster) {
+		return 0;
+	}
+
+	/* for instance if previous transfer was terminated due to TX error
+	 * it might be that the bus is on it's way to become available
+	 * give it at most 3 ms to wake
+	 */
+	err = xiic_bus_busy(i2c);
+	while (err && tries--) {
+		msleep(1);
+		err = xiic_bus_busy(i2c);
+	}
+
+	return err;
+}
+
+static void xiic_start_recv(struct xiic_i2c *i2c)
+{
+	u16 rx_watermark;
+	struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;
+
+	/* Clear and enable Rx full interrupt. */
+	xiic_irq_clr_en(i2c, 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;
+	xiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, (u8)(rx_watermark - 1));
+
+	if (!(msg->flags & I2C_M_NOSTART))
+		/* write the address */
+		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
+			i2c_8bit_addr_from_msg(msg) | XIIC_TX_DYN_START_MASK);
+
+	xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
+
+	xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET,
+		msg->len | ((i2c->nmsgs == 1) ? XIIC_TX_DYN_STOP_MASK : 0));
+
+	if (i2c->nmsgs == 1)
+		/* very last, enable bus not busy as well */
+		xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
+
+	/* the message is tx:ed */
+	i2c->tx_pos = msg->len;
+}
+
+static void xiic_start_send(struct xiic_i2c *i2c)
+{
+	struct i2c_msg *msg = i2c->tx_msg;
+
+	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
+		__func__, msg, msg->len);
+	dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
+		__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+
+	if (!(msg->flags & I2C_M_NOSTART)) {
+		/* write the address */
+		u16 data = i2c_8bit_addr_from_msg(msg) |
+			XIIC_TX_DYN_START_MASK;
+		if ((i2c->nmsgs == 1) && msg->len == 0)
+			/* no data and last message -> add STOP */
+			data |= XIIC_TX_DYN_STOP_MASK;
+
+		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+	}
+
+	/* Clear any pending Tx empty, Tx Error and then enable them. */
+	xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_ERROR_MASK |
+		XIIC_INTR_BNB_MASK |
+		((i2c->nmsgs > 1 || xiic_tx_space(i2c)) ?
+			XIIC_INTR_TX_HALF_MASK : 0));
+
+	xiic_fill_tx_fifo(i2c);
+}
+
+static void __xiic_start_xfer(struct xiic_i2c *i2c)
+{
+	int fifo_space = xiic_tx_fifo_space(i2c);
+
+	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
+		__func__, i2c->tx_msg, fifo_space);
+
+	if (!i2c->tx_msg)
+		return;
+
+	i2c->rx_pos = 0;
+	i2c->tx_pos = 0;
+	i2c->state = STATE_START;
+	if (i2c->tx_msg->flags & I2C_M_RD) {
+		/* we dont date putting several reads in the FIFO */
+		xiic_start_recv(i2c);
+	} else {
+		xiic_start_send(i2c);
+	}
+}
+
+static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
+{
+	int ret;
+
+	mutex_lock(&i2c->lock);
+
+	ret = xiic_busy(i2c);
+	if (ret)
+		goto out;
+
+	i2c->tx_msg = msgs;
+	i2c->rx_msg = NULL;
+	i2c->nmsgs = num;
+	init_completion(&i2c->completion);
+
+	ret = xiic_reinit(i2c);
+	if (!ret)
+		__xiic_start_xfer(i2c);
+
+out:
+	mutex_unlock(&i2c->lock);
+
+	return ret;
+}
+
+static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct xiic_i2c *i2c = i2c_get_adapdata(adap);
+	int err;
+
+	dev_dbg(adap->dev.parent, "%s entry SR: 0x%x\n", __func__,
+		xiic_getreg8(i2c, XIIC_SR_REG_OFFSET));
+
+	err = pm_runtime_resume_and_get(i2c->dev);
+	if (err < 0)
+		return err;
+
+	err = xiic_start_xfer(i2c, msgs, num);
+	if (err < 0) {
+		dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
+		goto out;
+	}
+
+	err = wait_for_completion_timeout(&i2c->completion, XIIC_XFER_TIMEOUT);
+	mutex_lock(&i2c->lock);
+	if (err == 0) {	/* Timeout */
+		i2c->tx_msg = NULL;
+		i2c->rx_msg = NULL;
+		i2c->nmsgs = 0;
+		err = -ETIMEDOUT;
+	} else if (err < 0) {	/* Completion error */
+		i2c->tx_msg = NULL;
+		i2c->rx_msg = NULL;
+		i2c->nmsgs = 0;
+	} else {
+		err = (i2c->state == STATE_DONE) ? num : -EIO;
+	}
+	mutex_unlock(&i2c->lock);
+
+out:
+	pm_runtime_mark_last_busy(i2c->dev);
+	pm_runtime_put_autosuspend(i2c->dev);
+	return err;
+}
+
+static u32 xiic_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm xiic_algorithm = {
+	.master_xfer = xiic_xfer,
+	.functionality = xiic_func,
+};
+
+static const struct i2c_adapter_quirks xiic_quirks = {
+	.max_read_len = 255,
+};
+
+static const struct i2c_adapter xiic_adapter = {
+	.owner = THIS_MODULE,
+	.class = I2C_CLASS_DEPRECATED,
+	.algo = &xiic_algorithm,
+	.quirks = &xiic_quirks,
+};
+
+static int xiic_i2c_probe(struct platform_device *pdev)
+{
+	struct xiic_i2c *i2c;
+	struct xiic_i2c_platform_data *pdata;
+	struct resource *res;
+	int ret, irq;
+	u8 i;
+	u32 sr;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(i2c->base))
+		return PTR_ERR(i2c->base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	pdata = dev_get_platdata(&pdev->dev);
+
+	/* hook up driver to tree */
+	platform_set_drvdata(pdev, i2c);
+	i2c->adap = xiic_adapter;
+	i2c_set_adapdata(&i2c->adap, i2c);
+	i2c->adap.dev.parent = &pdev->dev;
+	i2c->adap.dev.of_node = pdev->dev.of_node;
+	snprintf(i2c->adap.name, sizeof(i2c->adap.name),
+		 DRIVER_NAME " %s", pdev->name);
+
+	mutex_init(&i2c->lock);
+
+	i2c->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(i2c->clk),
+				     "input clock not found.\n");
+
+	ret = clk_prepare_enable(i2c->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Unable to enable clock.\n");
+		return ret;
+	}
+	i2c->dev = &pdev->dev;
+	pm_runtime_set_autosuspend_delay(i2c->dev, XIIC_PM_TIMEOUT);
+	pm_runtime_use_autosuspend(i2c->dev);
+	pm_runtime_set_active(i2c->dev);
+	pm_runtime_enable(i2c->dev);
+	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+					xiic_process, IRQF_ONESHOT,
+					pdev->name, i2c);
+
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Cannot claim IRQ\n");
+		goto err_clk_dis;
+	}
+
+	i2c->singlemaster =
+		of_property_read_bool(pdev->dev.of_node, "single-master");
+
+	/*
+	 * Detect endianness
+	 * Try to reset the TX FIFO. Then check the EMPTY flag. If it is not
+	 * set, assume that the endianness was wrong and swap.
+	 */
+	i2c->endianness = LITTLE;
+	xiic_setreg32(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK);
+	/* Reset is cleared in xiic_reinit */
+	sr = xiic_getreg32(i2c, XIIC_SR_REG_OFFSET);
+	if (!(sr & XIIC_SR_TX_FIFO_EMPTY_MASK))
+		i2c->endianness = BIG;
+
+	ret = xiic_reinit(i2c);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Cannot xiic_reinit\n");
+		goto err_clk_dis;
+	}
+
+	/* add i2c adapter to i2c tree */
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret) {
+		xiic_deinit(i2c);
+		goto err_clk_dis;
+	}
+
+	if (pdata) {
+		/* add in known devices to the bus */
+		for (i = 0; i < pdata->num_devices; i++)
+			i2c_new_client_device(&i2c->adap, pdata->devices + i);
+	}
+
+	return 0;
+
+err_clk_dis:
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	clk_disable_unprepare(i2c->clk);
+	return ret;
+}
+
+static int xiic_i2c_remove(struct platform_device *pdev)
+{
+	struct xiic_i2c *i2c = platform_get_drvdata(pdev);
+	int ret;
+
+	/* remove adapter & data */
+	i2c_del_adapter(&i2c->adap);
+
+	ret = pm_runtime_resume_and_get(i2c->dev);
+	if (ret < 0)
+		return ret;
+
+	xiic_deinit(i2c);
+	pm_runtime_put_sync(i2c->dev);
+	clk_disable_unprepare(i2c->clk);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_dont_use_autosuspend(&pdev->dev);
+
+	return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id xiic_of_match[] = {
+	{ .compatible = "xlnx,xps-iic-2.00.a", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, xiic_of_match);
+#endif
+
+static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
+{
+	struct xiic_i2c *i2c = dev_get_drvdata(dev);
+
+	clk_disable(i2c->clk);
+
+	return 0;
+}
+
+static int __maybe_unused xiic_i2c_runtime_resume(struct device *dev)
+{
+	struct xiic_i2c *i2c = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_enable(i2c->clk);
+	if (ret) {
+		dev_err(dev, "Cannot enable clock.\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops xiic_dev_pm_ops = {
+	SET_RUNTIME_PM_OPS(xiic_i2c_runtime_suspend,
+			   xiic_i2c_runtime_resume, NULL)
+};
+
+static struct platform_driver xiic_i2c_driver = {
+	.probe   = xiic_i2c_probe,
+	.remove  = xiic_i2c_remove,
+	.driver  = {
+		.name = DRIVER_NAME,
+		.of_match_table = of_match_ptr(xiic_of_match),
+		.pm = &xiic_dev_pm_ops,
+	},
+};
+
+module_platform_driver(xiic_i2c_driver);
+
+MODULE_ALIAS("platform:" DRIVER_NAME);
+MODULE_AUTHOR("info@mocean-labs.com");
+MODULE_DESCRIPTION("Xilinx I2C bus driver");
+MODULE_LICENSE("GPL v2");