drivers/i2c/busses/i2c-uniphier.c - arm/linux - Git at Google

 /*
  * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * 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.
  */

 #include <linux/clk.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>

 #define UNIPHIER_I2C_DTRM	0x00	/* TX register */
 #define     UNIPHIER_I2C_DTRM_IRQEN	BIT(11)	/* enable interrupt */
 #define     UNIPHIER_I2C_DTRM_STA	BIT(10)	/* start condition */
 #define     UNIPHIER_I2C_DTRM_STO	BIT(9)	/* stop condition */
 #define     UNIPHIER_I2C_DTRM_NACK	BIT(8)	/* do not return ACK */
 #define     UNIPHIER_I2C_DTRM_RD	BIT(0)	/* read transaction */
 #define UNIPHIER_I2C_DREC	0x04	/* RX register */
 #define     UNIPHIER_I2C_DREC_MST	BIT(14)	/* 1 = master, 0 = slave */
 #define     UNIPHIER_I2C_DREC_TX	BIT(13)	/* 1 = transmit, 0 = receive */
 #define     UNIPHIER_I2C_DREC_STS	BIT(12)	/* stop condition detected */
 #define     UNIPHIER_I2C_DREC_LRB	BIT(11)	/* no ACK */
 #define     UNIPHIER_I2C_DREC_LAB	BIT(9)	/* arbitration lost */
 #define     UNIPHIER_I2C_DREC_BBN	BIT(8)	/* bus not busy */
 #define UNIPHIER_I2C_MYAD	0x08	/* slave address */
 #define UNIPHIER_I2C_CLK	0x0c	/* clock frequency control */
 #define UNIPHIER_I2C_BRST	0x10	/* bus reset */
 #define     UNIPHIER_I2C_BRST_FOEN	BIT(1)	/* normal operation */
 #define     UNIPHIER_I2C_BRST_RSCL	BIT(0)	/* release SCL */
 #define UNIPHIER_I2C_HOLD	0x14	/* hold time control */
 #define UNIPHIER_I2C_BSTS	0x18	/* bus status monitor */
 #define     UNIPHIER_I2C_BSTS_SDA	BIT(1)	/* readback of SDA line */
 #define     UNIPHIER_I2C_BSTS_SCL	BIT(0)	/* readback of SCL line */
 #define UNIPHIER_I2C_NOISE	0x1c	/* noise filter control */
 #define UNIPHIER_I2C_SETUP	0x20	/* setup time control */

 #define UNIPHIER_I2C_DEFAULT_SPEED	100000
 #define UNIPHIER_I2C_MAX_SPEED		400000

 struct uniphier_i2c_priv {
 	struct completion comp;
 	struct i2c_adapter adap;
 	void __iomem *membase;
 	struct clk *clk;
 	unsigned int busy_cnt;
 	unsigned int clk_cycle;
 };

 static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)
 {
 	struct uniphier_i2c_priv *priv = dev_id;

 	/*
 	 * This hardware uses edge triggered interrupt.  Do not touch the
 	 * hardware registers in this handler to make sure to catch the next
 	 * interrupt edge.  Just send a complete signal and return.
 	 */
 	complete(&priv->comp);

 	return IRQ_HANDLED;
 }

 static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,
 				  u32 *rxdatap)
 {
 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
 	unsigned long time_left;
 	u32 rxdata;

 	reinit_completion(&priv->comp);

 	txdata |= UNIPHIER_I2C_DTRM_IRQEN;
 	dev_dbg(&adap->dev, "write data: 0x%04x\n", txdata);
 	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);

 	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
 	if (unlikely(!time_left)) {
 		dev_err(&adap->dev, "transaction timeout\n");
 		return -ETIMEDOUT;
 	}

 	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);
 	dev_dbg(&adap->dev, "read data: 0x%04x\n", rxdata);

 	if (rxdatap)
 		*rxdatap = rxdata;

 	return 0;
 }

 static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)
 {
 	u32 rxdata;
 	int ret;

 	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);
 	if (ret)
 		return ret;

 	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB)) {
 		dev_dbg(&adap->dev, "arbitration lost\n");
 		return -EAGAIN;
 	}
 	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB)) {
 		dev_dbg(&adap->dev, "could not get ACK\n");
 		return -ENXIO;
 	}

 	return 0;
 }

 static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,
 			   const u8 *buf)
 {
 	int ret;

 	dev_dbg(&adap->dev, "start condition\n");
 	ret = uniphier_i2c_send_byte(adap, addr << 1 |
 				     UNIPHIER_I2C_DTRM_STA |
 				     UNIPHIER_I2C_DTRM_NACK);
 	if (ret)
 		return ret;

 	while (len--) {
 		ret = uniphier_i2c_send_byte(adap,
 					     UNIPHIER_I2C_DTRM_NACK | *buf++);
 		if (ret)
 			return ret;
 	}

 	return 0;
 }

 static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,
 			   u8 *buf)
 {
 	int ret;

 	dev_dbg(&adap->dev, "start condition\n");
 	ret = uniphier_i2c_send_byte(adap, addr << 1 |
 				     UNIPHIER_I2C_DTRM_STA |
 				     UNIPHIER_I2C_DTRM_NACK |
 				     UNIPHIER_I2C_DTRM_RD);
 	if (ret)
 		return ret;

 	while (len--) {
 		u32 rxdata;

 		ret = uniphier_i2c_xfer_byte(adap,
 					     len ? 0 : UNIPHIER_I2C_DTRM_NACK,
 					     &rxdata);
 		if (ret)
 			return ret;
 		*buf++ = rxdata;
 	}

 	return 0;
 }

 static int uniphier_i2c_stop(struct i2c_adapter *adap)
 {
 	dev_dbg(&adap->dev, "stop condition\n");
 	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO |
 				      UNIPHIER_I2C_DTRM_NACK);
 }

 static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,
 					struct i2c_msg *msg, bool stop)
 {
 	bool is_read = msg->flags & I2C_M_RD;
 	bool recovery = false;
 	int ret;

 	dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d\n",
 		is_read ? "receive" : "transmit", msg->addr, msg->len, stop);

 	if (is_read)
 		ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);
 	else
 		ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);

 	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */
 		return ret;

 	if (ret == -ETIMEDOUT) {
 		/* This error is fatal.  Needs recovery. */
 		stop = false;
 		recovery = true;
 	}

 	if (stop) {
 		int ret2 = uniphier_i2c_stop(adap);

 		if (ret2) {
 			/* Failed to issue STOP.  The bus needs recovery. */
 			recovery = true;
 			ret = ret ?: ret2;
 		}
 	}

 	if (recovery)
 		i2c_recover_bus(adap);

 	return ret;
 }

 static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)
 {
 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

 	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &
 						UNIPHIER_I2C_DREC_BBN)) {
 		if (priv->busy_cnt++ > 3) {
 			/*
 			 * If bus busy continues too long, it is probably
 			 * in a wrong state.  Try bus recovery.
 			 */
 			i2c_recover_bus(adap);
 			priv->busy_cnt = 0;
 		}

 		return -EAGAIN;
 	}

 	priv->busy_cnt = 0;
 	return 0;
 }

 static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,
 				    struct i2c_msg *msgs, int num)
 {
 	struct i2c_msg *msg, *emsg = msgs + num;
 	int ret;

 	ret = uniphier_i2c_check_bus_busy(adap);
 	if (ret)
 		return ret;

 	for (msg = msgs; msg < emsg; msg++) {
 		/* If next message is read, skip the stop condition */
 		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
 		/* but, force it if I2C_M_STOP is set */
 		if (msg->flags & I2C_M_STOP)
 			stop = true;

 		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
 		if (ret)
 			return ret;
 	}

 	return num;
 }

 static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }

 static const struct i2c_algorithm uniphier_i2c_algo = {
 	.master_xfer = uniphier_i2c_master_xfer,
 	.functionality = uniphier_i2c_functionality,
 };

 static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)
 {
 	u32 val = UNIPHIER_I2C_BRST_RSCL;

 	val |= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;
 	writel(val, priv->membase + UNIPHIER_I2C_BRST);
 }

 static int uniphier_i2c_get_scl(struct i2c_adapter *adap)
 {
 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

 	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
 							UNIPHIER_I2C_BSTS_SCL);
 }

 static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)
 {
 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

 	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,
 	       priv->membase + UNIPHIER_I2C_BRST);
 }

 static int uniphier_i2c_get_sda(struct i2c_adapter *adap)
 {
 	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

 	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
 							UNIPHIER_I2C_BSTS_SDA);
 }

 static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)
 {
 	uniphier_i2c_reset(i2c_get_adapdata(adap), false);
 }

 static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
 	.recover_bus = i2c_generic_scl_recovery,
 	.get_scl = uniphier_i2c_get_scl,
 	.set_scl = uniphier_i2c_set_scl,
 	.get_sda = uniphier_i2c_get_sda,
 	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
 };

 static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv)
 {
 	unsigned int cyc = priv->clk_cycle;

 	uniphier_i2c_reset(priv, true);

 	writel((cyc / 2 << 16) | cyc, priv->membase + UNIPHIER_I2C_CLK);

 	uniphier_i2c_reset(priv, false);
 }

 static int uniphier_i2c_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct uniphier_i2c_priv *priv;
 	struct resource *regs;
 	u32 bus_speed;
 	unsigned long clk_rate;
 	int irq, ret;

 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	priv->membase = devm_ioremap_resource(dev, regs);
 	if (IS_ERR(priv->membase))
 		return PTR_ERR(priv->membase);

 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
 		dev_err(dev, "failed to get IRQ number\n");
 		return irq;
 	}

 	if (of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed))
 		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;

 	if (!bus_speed || bus_speed > UNIPHIER_I2C_MAX_SPEED) {
 		dev_err(dev, "invalid clock-frequency %d\n", bus_speed);
 		return -EINVAL;
 	}

 	priv->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(priv->clk)) {
 		dev_err(dev, "failed to get clock\n");
 		return PTR_ERR(priv->clk);
 	}

 	ret = clk_prepare_enable(priv->clk);
 	if (ret)
 		return ret;

 	clk_rate = clk_get_rate(priv->clk);
 	if (!clk_rate) {
 		dev_err(dev, "input clock rate should not be zero\n");
 		ret = -EINVAL;
 		goto disable_clk;
 	}

 	priv->clk_cycle = clk_rate / bus_speed;
 	init_completion(&priv->comp);
 	priv->adap.owner = THIS_MODULE;
 	priv->adap.algo = &uniphier_i2c_algo;
 	priv->adap.dev.parent = dev;
 	priv->adap.dev.of_node = dev->of_node;
 	strlcpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));
 	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;
 	i2c_set_adapdata(&priv->adap, priv);
 	platform_set_drvdata(pdev, priv);

 	uniphier_i2c_hw_init(priv);

 	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
 			       priv);
 	if (ret) {
 		dev_err(dev, "failed to request irq %d\n", irq);
 		goto disable_clk;
 	}

 	ret = i2c_add_adapter(&priv->adap);
 disable_clk:
 	if (ret)
 		clk_disable_unprepare(priv->clk);

 	return ret;
 }

 static int uniphier_i2c_remove(struct platform_device *pdev)
 {
 	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);

 	i2c_del_adapter(&priv->adap);
 	clk_disable_unprepare(priv->clk);

 	return 0;
 }

 static int __maybe_unused uniphier_i2c_suspend(struct device *dev)
 {
 	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);

 	clk_disable_unprepare(priv->clk);

 	return 0;
 }

 static int __maybe_unused uniphier_i2c_resume(struct device *dev)
 {
 	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);
 	int ret;

 	ret = clk_prepare_enable(priv->clk);
 	if (ret)
 		return ret;

 	uniphier_i2c_hw_init(priv);

 	return 0;
 }

 static const struct dev_pm_ops uniphier_i2c_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(uniphier_i2c_suspend, uniphier_i2c_resume)
 };

 static const struct of_device_id uniphier_i2c_match[] = {
 	{ .compatible = "socionext,uniphier-i2c" },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, uniphier_i2c_match);

 static struct platform_driver uniphier_i2c_drv = {
 	.probe  = uniphier_i2c_probe,
 	.remove = uniphier_i2c_remove,
 	.driver = {
 		.name  = "uniphier-i2c",
 		.of_match_table = uniphier_i2c_match,
 		.pm = &uniphier_i2c_pm_ops,
 	},
 };
 module_platform_driver(uniphier_i2c_drv);

 MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
 MODULE_DESCRIPTION("UniPhier I2C bus driver");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* 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.
	*/

	#include <linux/clk.h>
	#include <linux/i2c.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>

	#define UNIPHIER_I2C_DTRM 0x00 /* TX register */
	#define UNIPHIER_I2C_DTRM_IRQEN BIT(11) /* enable interrupt */
	#define UNIPHIER_I2C_DTRM_STA BIT(10) /* start condition */
	#define UNIPHIER_I2C_DTRM_STO BIT(9) /* stop condition */
	#define UNIPHIER_I2C_DTRM_NACK BIT(8) /* do not return ACK */
	#define UNIPHIER_I2C_DTRM_RD BIT(0) /* read transaction */
	#define UNIPHIER_I2C_DREC 0x04 /* RX register */
	#define UNIPHIER_I2C_DREC_MST BIT(14) /* 1 = master, 0 = slave */
	#define UNIPHIER_I2C_DREC_TX BIT(13) /* 1 = transmit, 0 = receive */
	#define UNIPHIER_I2C_DREC_STS BIT(12) /* stop condition detected */
	#define UNIPHIER_I2C_DREC_LRB BIT(11) /* no ACK */
	#define UNIPHIER_I2C_DREC_LAB BIT(9) /* arbitration lost */
	#define UNIPHIER_I2C_DREC_BBN BIT(8) /* bus not busy */
	#define UNIPHIER_I2C_MYAD 0x08 /* slave address */
	#define UNIPHIER_I2C_CLK 0x0c /* clock frequency control */
	#define UNIPHIER_I2C_BRST 0x10 /* bus reset */
	#define UNIPHIER_I2C_BRST_FOEN BIT(1) /* normal operation */
	#define UNIPHIER_I2C_BRST_RSCL BIT(0) /* release SCL */
	#define UNIPHIER_I2C_HOLD 0x14 /* hold time control */
	#define UNIPHIER_I2C_BSTS 0x18 /* bus status monitor */
	#define UNIPHIER_I2C_BSTS_SDA BIT(1) /* readback of SDA line */
	#define UNIPHIER_I2C_BSTS_SCL BIT(0) /* readback of SCL line */
	#define UNIPHIER_I2C_NOISE 0x1c /* noise filter control */
	#define UNIPHIER_I2C_SETUP 0x20 /* setup time control */

	#define UNIPHIER_I2C_DEFAULT_SPEED 100000
	#define UNIPHIER_I2C_MAX_SPEED 400000

	struct uniphier_i2c_priv {
	struct completion comp;
	struct i2c_adapter adap;
	void __iomem *membase;
	struct clk *clk;
	unsigned int busy_cnt;
	unsigned int clk_cycle;
	};

	static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)
	{
	struct uniphier_i2c_priv *priv = dev_id;

	/*
	* This hardware uses edge triggered interrupt. Do not touch the
	* hardware registers in this handler to make sure to catch the next
	* interrupt edge. Just send a complete signal and return.
	*/
	complete(&priv->comp);

	return IRQ_HANDLED;
	}

	static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,
	u32 *rxdatap)
	{
	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
	unsigned long time_left;
	u32 rxdata;

	reinit_completion(&priv->comp);

	txdata \|= UNIPHIER_I2C_DTRM_IRQEN;
	dev_dbg(&adap->dev, "write data: 0x%04x\n", txdata);
	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);

	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
	if (unlikely(!time_left)) {
	dev_err(&adap->dev, "transaction timeout\n");
	return -ETIMEDOUT;
	}

	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);
	dev_dbg(&adap->dev, "read data: 0x%04x\n", rxdata);

	if (rxdatap)
	*rxdatap = rxdata;

	return 0;
	}

	static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)
	{
	u32 rxdata;
	int ret;

	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);
	if (ret)
	return ret;

	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB)) {
	dev_dbg(&adap->dev, "arbitration lost\n");
	return -EAGAIN;
	}
	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB)) {
	dev_dbg(&adap->dev, "could not get ACK\n");
	return -ENXIO;
	}

	return 0;
	}

	static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,
	const u8 *buf)
	{
	int ret;

	dev_dbg(&adap->dev, "start condition\n");
	ret = uniphier_i2c_send_byte(adap, addr << 1 \|
	UNIPHIER_I2C_DTRM_STA \|
	UNIPHIER_I2C_DTRM_NACK);
	if (ret)
	return ret;

	while (len--) {
	ret = uniphier_i2c_send_byte(adap,
	UNIPHIER_I2C_DTRM_NACK \| *buf++);
	if (ret)
	return ret;
	}

	return 0;
	}

	static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,
	u8 *buf)
	{
	int ret;

	dev_dbg(&adap->dev, "start condition\n");
	ret = uniphier_i2c_send_byte(adap, addr << 1 \|
	UNIPHIER_I2C_DTRM_STA \|
	UNIPHIER_I2C_DTRM_NACK \|
	UNIPHIER_I2C_DTRM_RD);
	if (ret)
	return ret;

	while (len--) {
	u32 rxdata;

	ret = uniphier_i2c_xfer_byte(adap,
	len ? 0 : UNIPHIER_I2C_DTRM_NACK,
	&rxdata);
	if (ret)
	return ret;
	*buf++ = rxdata;
	}

	return 0;
	}

	static int uniphier_i2c_stop(struct i2c_adapter *adap)
	{
	dev_dbg(&adap->dev, "stop condition\n");
	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO \|
	UNIPHIER_I2C_DTRM_NACK);
	}

	static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,
	struct i2c_msg *msg, bool stop)
	{
	bool is_read = msg->flags & I2C_M_RD;
	bool recovery = false;
	int ret;

	dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d\n",
	is_read ? "receive" : "transmit", msg->addr, msg->len, stop);

	if (is_read)
	ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);
	else
	ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);

	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */
	return ret;

	if (ret == -ETIMEDOUT) {
	/* This error is fatal. Needs recovery. */
	stop = false;
	recovery = true;
	}

	if (stop) {
	int ret2 = uniphier_i2c_stop(adap);

	if (ret2) {
	/* Failed to issue STOP. The bus needs recovery. */
	recovery = true;
	ret = ret ?: ret2;
	}
	}

	if (recovery)
	i2c_recover_bus(adap);

	return ret;
	}

	static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)
	{
	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &
	UNIPHIER_I2C_DREC_BBN)) {
	if (priv->busy_cnt++ > 3) {
	/*
	* If bus busy continues too long, it is probably
	* in a wrong state. Try bus recovery.
	*/
	i2c_recover_bus(adap);
	priv->busy_cnt = 0;
	}

	return -EAGAIN;
	}

	priv->busy_cnt = 0;
	return 0;
	}

	static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,
	struct i2c_msg *msgs, int num)
	{
	struct i2c_msg msg, emsg = msgs + num;
	int ret;

	ret = uniphier_i2c_check_bus_busy(adap);
	if (ret)
	return ret;

	for (msg = msgs; msg < emsg; msg++) {
	/* If next message is read, skip the stop condition */
	bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
	/* but, force it if I2C_M_STOP is set */
	if (msg->flags & I2C_M_STOP)
	stop = true;

	ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
	if (ret)
	return ret;
	}

	return num;
	}

	static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)
	{
	return I2C_FUNC_I2C \| I2C_FUNC_SMBUS_EMUL;
	}

	static const struct i2c_algorithm uniphier_i2c_algo = {
	.master_xfer = uniphier_i2c_master_xfer,
	.functionality = uniphier_i2c_functionality,
	};

	static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)
	{
	u32 val = UNIPHIER_I2C_BRST_RSCL;

	val \|= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;
	writel(val, priv->membase + UNIPHIER_I2C_BRST);
	}

	static int uniphier_i2c_get_scl(struct i2c_adapter *adap)
	{
	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
	UNIPHIER_I2C_BSTS_SCL);
	}

	static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)
	{
	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,
	priv->membase + UNIPHIER_I2C_BRST);
	}

	static int uniphier_i2c_get_sda(struct i2c_adapter *adap)
	{
	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);

	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
	UNIPHIER_I2C_BSTS_SDA);
	}

	static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)
	{
	uniphier_i2c_reset(i2c_get_adapdata(adap), false);
	}

	static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
	.recover_bus = i2c_generic_scl_recovery,
	.get_scl = uniphier_i2c_get_scl,
	.set_scl = uniphier_i2c_set_scl,
	.get_sda = uniphier_i2c_get_sda,
	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
	};

	static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv)
	{
	unsigned int cyc = priv->clk_cycle;

	uniphier_i2c_reset(priv, true);

	writel((cyc / 2 << 16) \| cyc, priv->membase + UNIPHIER_I2C_CLK);

	uniphier_i2c_reset(priv, false);
	}

	static int uniphier_i2c_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct uniphier_i2c_priv *priv;
	struct resource *regs;
	u32 bus_speed;
	unsigned long clk_rate;
	int irq, ret;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	priv->membase = devm_ioremap_resource(dev, regs);
	if (IS_ERR(priv->membase))
	return PTR_ERR(priv->membase);

	irq = platform_get_irq(pdev, 0);
	if (irq < 0) {
	dev_err(dev, "failed to get IRQ number\n");
	return irq;
	}

	if (of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed))
	bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;

	if (!bus_speed \|\| bus_speed > UNIPHIER_I2C_MAX_SPEED) {
	dev_err(dev, "invalid clock-frequency %d\n", bus_speed);
	return -EINVAL;
	}

	priv->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(priv->clk)) {
	dev_err(dev, "failed to get clock\n");
	return PTR_ERR(priv->clk);
	}

	ret = clk_prepare_enable(priv->clk);
	if (ret)
	return ret;

	clk_rate = clk_get_rate(priv->clk);
	if (!clk_rate) {
	dev_err(dev, "input clock rate should not be zero\n");
	ret = -EINVAL;
	goto disable_clk;
	}

	priv->clk_cycle = clk_rate / bus_speed;
	init_completion(&priv->comp);
	priv->adap.owner = THIS_MODULE;
	priv->adap.algo = &uniphier_i2c_algo;
	priv->adap.dev.parent = dev;
	priv->adap.dev.of_node = dev->of_node;
	strlcpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));
	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;
	i2c_set_adapdata(&priv->adap, priv);
	platform_set_drvdata(pdev, priv);

	uniphier_i2c_hw_init(priv);

	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
	priv);
	if (ret) {
	dev_err(dev, "failed to request irq %d\n", irq);
	goto disable_clk;
	}

	ret = i2c_add_adapter(&priv->adap);
	disable_clk:
	if (ret)
	clk_disable_unprepare(priv->clk);

	return ret;
	}

	static int uniphier_i2c_remove(struct platform_device *pdev)
	{
	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);

	i2c_del_adapter(&priv->adap);
	clk_disable_unprepare(priv->clk);

	return 0;
	}

	static int __maybe_unused uniphier_i2c_suspend(struct device *dev)
	{
	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);

	clk_disable_unprepare(priv->clk);

	return 0;
	}

	static int __maybe_unused uniphier_i2c_resume(struct device *dev)
	{
	struct uniphier_i2c_priv *priv = dev_get_drvdata(dev);
	int ret;

	ret = clk_prepare_enable(priv->clk);
	if (ret)
	return ret;

	uniphier_i2c_hw_init(priv);

	return 0;
	}

	static const struct dev_pm_ops uniphier_i2c_pm_ops = {
	SET_SYSTEM_SLEEP_PM_OPS(uniphier_i2c_suspend, uniphier_i2c_resume)
	};

	static const struct of_device_id uniphier_i2c_match[] = {
	{ .compatible = "socionext,uniphier-i2c" },
	{ /* sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, uniphier_i2c_match);

	static struct platform_driver uniphier_i2c_drv = {
	.probe = uniphier_i2c_probe,
	.remove = uniphier_i2c_remove,
	.driver = {
	.name = "uniphier-i2c",
	.of_match_table = uniphier_i2c_match,
	.pm = &uniphier_i2c_pm_ops,
	},
	};
	module_platform_driver(uniphier_i2c_drv);

	MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
	MODULE_DESCRIPTION("UniPhier I2C bus driver");
	MODULE_LICENSE("GPL");