drivers/i2c/busses/i2c-riic.c - third_party/linux - Git at Google

 /*
  * Renesas RIIC driver
  *
  * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
  * Copyright (C) 2013 Renesas Solutions Corp.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published by
  * the Free Software Foundation.
  */

 /*
  * This i2c core has a lot of interrupts, namely 8. We use their chaining as
  * some kind of state machine.
  *
  * 1) The main xfer routine kicks off a transmission by putting the start bit
  * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
  * since we need to send the slave address + RW bit in every case.
  *
  * 2) TIE sends slave address + RW bit and selects how to continue.
  *
  * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
  * are done, we switch over to the transmission done interrupt (TEIE) and mark
  * the message as completed (includes sending STOP) there.
  *
  * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
  * needed to start clocking, then we keep receiving until we are done. Note
  * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
  * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
  * message to create the final NACK as sketched in the datasheet. This caused
  * some subtle races (when byte n was processed and byte n+1 was already
  * waiting), though, and I started with the safe approach.
  *
  * 4) If we got a NACK somewhere, we flag the error and stop the transmission
  * via NAKIE.
  *
  * Also check the comments in the interrupt routines for some gory details.
  */

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

 #define RIIC_ICCR1	0x00
 #define RIIC_ICCR2	0x04
 #define RIIC_ICMR1	0x08
 #define RIIC_ICMR3	0x10
 #define RIIC_ICSER	0x18
 #define RIIC_ICIER	0x1c
 #define RIIC_ICSR2	0x24
 #define RIIC_ICBRL	0x34
 #define RIIC_ICBRH	0x38
 #define RIIC_ICDRT	0x3c
 #define RIIC_ICDRR	0x40

 #define ICCR1_ICE	0x80
 #define ICCR1_IICRST	0x40
 #define ICCR1_SOWP	0x10

 #define ICCR2_BBSY	0x80
 #define ICCR2_SP	0x08
 #define ICCR2_RS	0x04
 #define ICCR2_ST	0x02

 #define ICMR1_CKS_MASK	0x70
 #define ICMR1_BCWP	0x08
 #define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)

 #define ICMR3_RDRFS	0x20
 #define ICMR3_ACKWP	0x10
 #define ICMR3_ACKBT	0x08

 #define ICIER_TIE	0x80
 #define ICIER_TEIE	0x40
 #define ICIER_RIE	0x20
 #define ICIER_NAKIE	0x10
 #define ICIER_SPIE	0x08

 #define ICSR2_NACKF	0x10

 #define ICBR_RESERVED	0xe0 /* Should be 1 on writes */

 #define RIIC_INIT_MSG	-1

 struct riic_dev {
 	void __iomem *base;
 	u8 *buf;
 	struct i2c_msg *msg;
 	int bytes_left;
 	int err;
 	int is_last;
 	struct completion msg_done;
 	struct i2c_adapter adapter;
 	struct clk *clk;
 };

 struct riic_irq_desc {
 	int res_num;
 	irq_handler_t isr;
 	char *name;
 };

 static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
 {
 	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
 }

 static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 {
 	struct riic_dev *riic = i2c_get_adapdata(adap);
 	unsigned long time_left;
 	int i, ret;
 	u8 start_bit;

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

 	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
 		riic->err = -EBUSY;
 		goto out;
 	}

 	reinit_completion(&riic->msg_done);
 	riic->err = 0;

 	writeb(0, riic->base + RIIC_ICSR2);

 	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
 		riic->bytes_left = RIIC_INIT_MSG;
 		riic->buf = msgs[i].buf;
 		riic->msg = &msgs[i];
 		riic->is_last = (i == num - 1);

 		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);

 		writeb(start_bit, riic->base + RIIC_ICCR2);

 		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
 		if (time_left == 0)
 			riic->err = -ETIMEDOUT;

 		if (riic->err)
 			break;

 		start_bit = ICCR2_RS;
 	}

  out:
 	clk_disable_unprepare(riic->clk);

 	return riic->err ?: num;
 }

 static irqreturn_t riic_tdre_isr(int irq, void *data)
 {
 	struct riic_dev *riic = data;
 	u8 val;

 	if (!riic->bytes_left)
 		return IRQ_NONE;

 	if (riic->bytes_left == RIIC_INIT_MSG) {
 		if (riic->msg->flags & I2C_M_RD)
 			/* On read, switch over to receive interrupt */
 			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
 		else
 			/* On write, initialize length */
 			riic->bytes_left = riic->msg->len;

 		val = i2c_8bit_addr_from_msg(riic->msg);
 	} else {
 		val = *riic->buf;
 		riic->buf++;
 		riic->bytes_left--;
 	}

 	/*
 	 * Switch to transmission ended interrupt when done. Do check here
 	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
 	 * 0 length then)
 	 */
 	if (riic->bytes_left == 0)
 		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);

 	/*
 	 * This acks the TIE interrupt. We get another TIE immediately if our
 	 * value could be moved to the shadow shift register right away. So
 	 * this must be after updates to ICIER (where we want to disable TIE)!
 	 */
 	writeb(val, riic->base + RIIC_ICDRT);

 	return IRQ_HANDLED;
 }

 static irqreturn_t riic_tend_isr(int irq, void *data)
 {
 	struct riic_dev *riic = data;

 	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
 		/* We got a NACKIE */
 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
 		riic->err = -ENXIO;
 	} else if (riic->bytes_left) {
 		return IRQ_NONE;
 	}

 	if (riic->is_last || riic->err) {
 		riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
 		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
 	} else {
 		/* Transfer is complete, but do not send STOP */
 		riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
 		complete(&riic->msg_done);
 	}

 	return IRQ_HANDLED;
 }

 static irqreturn_t riic_rdrf_isr(int irq, void *data)
 {
 	struct riic_dev *riic = data;

 	if (!riic->bytes_left)
 		return IRQ_NONE;

 	if (riic->bytes_left == RIIC_INIT_MSG) {
 		riic->bytes_left = riic->msg->len;
 		readb(riic->base + RIIC_ICDRR);	/* dummy read */
 		return IRQ_HANDLED;
 	}

 	if (riic->bytes_left == 1) {
 		/* STOP must come before we set ACKBT! */
 		if (riic->is_last) {
 			riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
 			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
 		}

 		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);

 	} else {
 		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
 	}

 	/* Reading acks the RIE interrupt */
 	*riic->buf = readb(riic->base + RIIC_ICDRR);
 	riic->buf++;
 	riic->bytes_left--;

 	return IRQ_HANDLED;
 }

 static irqreturn_t riic_stop_isr(int irq, void *data)
 {
 	struct riic_dev *riic = data;

 	/* read back registers to confirm writes have fully propagated */
 	writeb(0, riic->base + RIIC_ICSR2);
 	readb(riic->base + RIIC_ICSR2);
 	writeb(0, riic->base + RIIC_ICIER);
 	readb(riic->base + RIIC_ICIER);

 	complete(&riic->msg_done);

 	return IRQ_HANDLED;
 }

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

 static const struct i2c_algorithm riic_algo = {
 	.master_xfer	= riic_xfer,
 	.functionality	= riic_func,
 };

 static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
 {
 	int ret;
 	unsigned long rate;
 	int total_ticks, cks, brl, brh;

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

 	if (t->bus_freq_hz > 400000) {
 		dev_err(&riic->adapter.dev,
 			"unsupported bus speed (%dHz). 400000 max\n",
 			t->bus_freq_hz);
 		clk_disable_unprepare(riic->clk);
 		return -EINVAL;
 	}

 	rate = clk_get_rate(riic->clk);

 	/*
 	 * Assume the default register settings:
 	 *  FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
 	 *  FER.NFE = 1 (noise circuit enabled)
 	 *  MR3.NF = 0 (1 cycle of noise filtered out)
 	 *
 	 * Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
 	 * Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
 	 */

 	/*
 	 * Determine reference clock rate. We must be able to get the desired
 	 * frequency with only 62 clock ticks max (31 high, 31 low).
 	 * Aim for a duty of 60% LOW, 40% HIGH.
 	 */
 	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);

 	for (cks = 0; cks < 7; cks++) {
 		/*
 		 * 60% low time must be less than BRL + 2 + 1
 		 * BRL max register value is 0x1F.
 		 */
 		brl = ((total_ticks * 6) / 10);
 		if (brl <= (0x1F + 3))
 			break;

 		total_ticks /= 2;
 		rate /= 2;
 	}

 	if (brl > (0x1F + 3)) {
 		dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
 			(unsigned long)t->bus_freq_hz);
 		clk_disable_unprepare(riic->clk);
 		return -EINVAL;
 	}

 	brh = total_ticks - brl;

 	/* Remove automatic clock ticks for sync circuit and NF */
 	if (cks == 0) {
 		brl -= 4;
 		brh -= 4;
 	} else {
 		brl -= 3;
 		brh -= 3;
 	}

 	/*
 	 * Remove clock ticks for rise and fall times. Convert ns to clock
 	 * ticks.
 	 */
 	brl -= t->scl_fall_ns / (1000000000 / rate);
 	brh -= t->scl_rise_ns / (1000000000 / rate);

 	/* Adjust for min register values for when SCLE=1 and NFE=1 */
 	if (brl < 1)
 		brl = 1;
 	if (brh < 1)
 		brh = 1;

 	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
 		 rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
 		 t->scl_fall_ns / (1000000000 / rate),
 		 t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);

 	/* Changing the order of accessing IICRST and ICE may break things! */
 	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
 	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);

 	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
 	writeb(brh | ICBR_RESERVED, riic->base + RIIC_ICBRH);
 	writeb(brl | ICBR_RESERVED, riic->base + RIIC_ICBRL);

 	writeb(0, riic->base + RIIC_ICSER);
 	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);

 	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);

 	clk_disable_unprepare(riic->clk);

 	return 0;
 }

 static struct riic_irq_desc riic_irqs[] = {
 	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
 	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
 	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
 	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
 	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
 };

 static int riic_i2c_probe(struct platform_device *pdev)
 {
 	struct riic_dev *riic;
 	struct i2c_adapter *adap;
 	struct resource *res;
 	struct i2c_timings i2c_t;
 	int i, ret;

 	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
 	if (!riic)
 		return -ENOMEM;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	riic->base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(riic->base))
 		return PTR_ERR(riic->base);

 	riic->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(riic->clk)) {
 		dev_err(&pdev->dev, "missing controller clock");
 		return PTR_ERR(riic->clk);
 	}

 	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
 		res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
 		if (!res)
 			return -ENODEV;

 		ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
 					0, riic_irqs[i].name, riic);
 		if (ret) {
 			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
 			return ret;
 		}
 	}

 	adap = &riic->adapter;
 	i2c_set_adapdata(adap, riic);
 	strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
 	adap->owner = THIS_MODULE;
 	adap->algo = &riic_algo;
 	adap->dev.parent = &pdev->dev;
 	adap->dev.of_node = pdev->dev.of_node;

 	init_completion(&riic->msg_done);

 	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);

 	ret = riic_init_hw(riic, &i2c_t);
 	if (ret)
 		return ret;


 	ret = i2c_add_adapter(adap);
 	if (ret)
 		return ret;

 	platform_set_drvdata(pdev, riic);

 	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
 		 i2c_t.bus_freq_hz);
 	return 0;
 }

 static int riic_i2c_remove(struct platform_device *pdev)
 {
 	struct riic_dev *riic = platform_get_drvdata(pdev);

 	writeb(0, riic->base + RIIC_ICIER);
 	i2c_del_adapter(&riic->adapter);

 	return 0;
 }

 static const struct of_device_id riic_i2c_dt_ids[] = {
 	{ .compatible = "renesas,riic-rz" },
 	{ /* Sentinel */ },
 };

 static struct platform_driver riic_i2c_driver = {
 	.probe		= riic_i2c_probe,
 	.remove		= riic_i2c_remove,
 	.driver		= {
 		.name	= "i2c-riic",
 		.of_match_table = riic_i2c_dt_ids,
 	},
 };

 module_platform_driver(riic_i2c_driver);

 MODULE_DESCRIPTION("Renesas RIIC adapter");
 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 MODULE_LICENSE("GPL v2");
 MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);
	/*
	* Renesas RIIC driver
	*
	* Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
	* Copyright (C) 2013 Renesas Solutions Corp.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 as published by
	* the Free Software Foundation.
	*/

	/*
	* This i2c core has a lot of interrupts, namely 8. We use their chaining as
	* some kind of state machine.
	*
	* 1) The main xfer routine kicks off a transmission by putting the start bit
	* (or repeated start) on the bus and enabling the transmit interrupt (TIE)
	* since we need to send the slave address + RW bit in every case.
	*
	* 2) TIE sends slave address + RW bit and selects how to continue.
	*
	* 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
	* are done, we switch over to the transmission done interrupt (TEIE) and mark
	* the message as completed (includes sending STOP) there.
	*
	* 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
	* needed to start clocking, then we keep receiving until we are done. Note
	* that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
	* writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
	* message to create the final NACK as sketched in the datasheet. This caused
	* some subtle races (when byte n was processed and byte n+1 was already
	* waiting), though, and I started with the safe approach.
	*
	* 4) If we got a NACK somewhere, we flag the error and stop the transmission
	* via NAKIE.
	*
	* Also check the comments in the interrupt routines for some gory details.
	*/

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

	#define RIIC_ICCR1 0x00
	#define RIIC_ICCR2 0x04
	#define RIIC_ICMR1 0x08
	#define RIIC_ICMR3 0x10
	#define RIIC_ICSER 0x18
	#define RIIC_ICIER 0x1c
	#define RIIC_ICSR2 0x24
	#define RIIC_ICBRL 0x34
	#define RIIC_ICBRH 0x38
	#define RIIC_ICDRT 0x3c
	#define RIIC_ICDRR 0x40

	#define ICCR1_ICE 0x80
	#define ICCR1_IICRST 0x40
	#define ICCR1_SOWP 0x10

	#define ICCR2_BBSY 0x80
	#define ICCR2_SP 0x08
	#define ICCR2_RS 0x04
	#define ICCR2_ST 0x02

	#define ICMR1_CKS_MASK 0x70
	#define ICMR1_BCWP 0x08
	#define ICMR1_CKS(_x) ((((_x) << 4) & ICMR1_CKS_MASK) \| ICMR1_BCWP)

	#define ICMR3_RDRFS 0x20
	#define ICMR3_ACKWP 0x10
	#define ICMR3_ACKBT 0x08

	#define ICIER_TIE 0x80
	#define ICIER_TEIE 0x40
	#define ICIER_RIE 0x20
	#define ICIER_NAKIE 0x10
	#define ICIER_SPIE 0x08

	#define ICSR2_NACKF 0x10

	#define ICBR_RESERVED 0xe0 /* Should be 1 on writes */

	#define RIIC_INIT_MSG -1

	struct riic_dev {
	void __iomem *base;
	u8 *buf;
	struct i2c_msg *msg;
	int bytes_left;
	int err;
	int is_last;
	struct completion msg_done;
	struct i2c_adapter adapter;
	struct clk *clk;
	};

	struct riic_irq_desc {
	int res_num;
	irq_handler_t isr;
	char *name;
	};

	static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
	{
	writeb((readb(riic->base + reg) & ~clear) \| set, riic->base + reg);
	}

	static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
	{
	struct riic_dev *riic = i2c_get_adapdata(adap);
	unsigned long time_left;
	int i, ret;
	u8 start_bit;

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

	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
	riic->err = -EBUSY;
	goto out;
	}

	reinit_completion(&riic->msg_done);
	riic->err = 0;

	writeb(0, riic->base + RIIC_ICSR2);

	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
	riic->bytes_left = RIIC_INIT_MSG;
	riic->buf = msgs[i].buf;
	riic->msg = &msgs[i];
	riic->is_last = (i == num - 1);

	writeb(ICIER_NAKIE \| ICIER_TIE, riic->base + RIIC_ICIER);

	writeb(start_bit, riic->base + RIIC_ICCR2);

	time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
	if (time_left == 0)
	riic->err = -ETIMEDOUT;

	if (riic->err)
	break;

	start_bit = ICCR2_RS;
	}

	out:
	clk_disable_unprepare(riic->clk);

	return riic->err ?: num;
	}

	static irqreturn_t riic_tdre_isr(int irq, void *data)
	{
	struct riic_dev *riic = data;
	u8 val;

	if (!riic->bytes_left)
	return IRQ_NONE;

	if (riic->bytes_left == RIIC_INIT_MSG) {
	if (riic->msg->flags & I2C_M_RD)
	/* On read, switch over to receive interrupt */
	riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
	else
	/* On write, initialize length */
	riic->bytes_left = riic->msg->len;

	val = i2c_8bit_addr_from_msg(riic->msg);
	} else {
	val = *riic->buf;
	riic->buf++;
	riic->bytes_left--;
	}

	/*
	* Switch to transmission ended interrupt when done. Do check here
	* after bytes_left was initialized to support SMBUS_QUICK (new msg has
	* 0 length then)
	*/
	if (riic->bytes_left == 0)
	riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);

	/*
	* This acks the TIE interrupt. We get another TIE immediately if our
	* value could be moved to the shadow shift register right away. So
	* this must be after updates to ICIER (where we want to disable TIE)!
	*/
	writeb(val, riic->base + RIIC_ICDRT);

	return IRQ_HANDLED;
	}

	static irqreturn_t riic_tend_isr(int irq, void *data)
	{
	struct riic_dev *riic = data;

	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
	/* We got a NACKIE */
	readb(riic->base + RIIC_ICDRR); /* dummy read */
	riic->err = -ENXIO;
	} else if (riic->bytes_left) {
	return IRQ_NONE;
	}

	if (riic->is_last \|\| riic->err) {
	riic_clear_set_bit(riic, ICIER_TEIE, ICIER_SPIE, RIIC_ICIER);
	writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
	} else {
	/* Transfer is complete, but do not send STOP */
	riic_clear_set_bit(riic, ICIER_TEIE, 0, RIIC_ICIER);
	complete(&riic->msg_done);
	}

	return IRQ_HANDLED;
	}

	static irqreturn_t riic_rdrf_isr(int irq, void *data)
	{
	struct riic_dev *riic = data;

	if (!riic->bytes_left)
	return IRQ_NONE;

	if (riic->bytes_left == RIIC_INIT_MSG) {
	riic->bytes_left = riic->msg->len;
	readb(riic->base + RIIC_ICDRR); /* dummy read */
	return IRQ_HANDLED;
	}

	if (riic->bytes_left == 1) {
	/* STOP must come before we set ACKBT! */
	if (riic->is_last) {
	riic_clear_set_bit(riic, 0, ICIER_SPIE, RIIC_ICIER);
	writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
	}

	riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);

	} else {
	riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
	}

	/* Reading acks the RIE interrupt */
	*riic->buf = readb(riic->base + RIIC_ICDRR);
	riic->buf++;
	riic->bytes_left--;

	return IRQ_HANDLED;
	}

	static irqreturn_t riic_stop_isr(int irq, void *data)
	{
	struct riic_dev *riic = data;

	/* read back registers to confirm writes have fully propagated */
	writeb(0, riic->base + RIIC_ICSR2);
	readb(riic->base + RIIC_ICSR2);
	writeb(0, riic->base + RIIC_ICIER);
	readb(riic->base + RIIC_ICIER);

	complete(&riic->msg_done);

	return IRQ_HANDLED;
	}

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

	static const struct i2c_algorithm riic_algo = {
	.master_xfer = riic_xfer,
	.functionality = riic_func,
	};

	static int riic_init_hw(struct riic_dev riic, struct i2c_timings t)
	{
	int ret;
	unsigned long rate;
	int total_ticks, cks, brl, brh;

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

	if (t->bus_freq_hz > 400000) {
	dev_err(&riic->adapter.dev,
	"unsupported bus speed (%dHz). 400000 max\n",
	t->bus_freq_hz);
	clk_disable_unprepare(riic->clk);
	return -EINVAL;
	}

	rate = clk_get_rate(riic->clk);

	/*
	* Assume the default register settings:
	* FER.SCLE = 1 (SCL sync circuit enabled, adds 2 or 3 cycles)
	* FER.NFE = 1 (noise circuit enabled)
	* MR3.NF = 0 (1 cycle of noise filtered out)
	*
	* Freq (CKS=000) = (I2CCLK + tr + tf)/ (BRH + 3 + 1) + (BRL + 3 + 1)
	* Freq (CKS!=000) = (I2CCLK + tr + tf)/ (BRH + 2 + 1) + (BRL + 2 + 1)
	*/

	/*
	* Determine reference clock rate. We must be able to get the desired
	* frequency with only 62 clock ticks max (31 high, 31 low).
	* Aim for a duty of 60% LOW, 40% HIGH.
	*/
	total_ticks = DIV_ROUND_UP(rate, t->bus_freq_hz);

	for (cks = 0; cks < 7; cks++) {
	/*
	* 60% low time must be less than BRL + 2 + 1
	* BRL max register value is 0x1F.
	*/
	brl = ((total_ticks * 6) / 10);
	if (brl <= (0x1F + 3))
	break;

	total_ticks /= 2;
	rate /= 2;
	}

	if (brl > (0x1F + 3)) {
	dev_err(&riic->adapter.dev, "invalid speed (%lu). Too slow.\n",
	(unsigned long)t->bus_freq_hz);
	clk_disable_unprepare(riic->clk);
	return -EINVAL;
	}

	brh = total_ticks - brl;

	/* Remove automatic clock ticks for sync circuit and NF */
	if (cks == 0) {
	brl -= 4;
	brh -= 4;
	} else {
	brl -= 3;
	brh -= 3;
	}

	/*
	* Remove clock ticks for rise and fall times. Convert ns to clock
	* ticks.
	*/
	brl -= t->scl_fall_ns / (1000000000 / rate);
	brh -= t->scl_rise_ns / (1000000000 / rate);

	/* Adjust for min register values for when SCLE=1 and NFE=1 */
	if (brl < 1)
	brl = 1;
	if (brh < 1)
	brh = 1;

	pr_debug("i2c-riic: freq=%lu, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
	rate / total_ticks, ((brl + 3) * 100) / (brl + brh + 6),
	t->scl_fall_ns / (1000000000 / rate),
	t->scl_rise_ns / (1000000000 / rate), cks, brl, brh);

	/* Changing the order of accessing IICRST and ICE may break things! */
	writeb(ICCR1_IICRST \| ICCR1_SOWP, riic->base + RIIC_ICCR1);
	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);

	writeb(ICMR1_CKS(cks), riic->base + RIIC_ICMR1);
	writeb(brh \| ICBR_RESERVED, riic->base + RIIC_ICBRH);
	writeb(brl \| ICBR_RESERVED, riic->base + RIIC_ICBRL);

	writeb(0, riic->base + RIIC_ICSER);
	writeb(ICMR3_ACKWP \| ICMR3_RDRFS, riic->base + RIIC_ICMR3);

	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);

	clk_disable_unprepare(riic->clk);

	return 0;
	}

	static struct riic_irq_desc riic_irqs[] = {
	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
	{ .res_num = 3, .isr = riic_stop_isr, .name = "riic-stop" },
	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
	};

	static int riic_i2c_probe(struct platform_device *pdev)
	{
	struct riic_dev *riic;
	struct i2c_adapter *adap;
	struct resource *res;
	struct i2c_timings i2c_t;
	int i, ret;

	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
	if (!riic)
	return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	riic->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(riic->base))
	return PTR_ERR(riic->base);

	riic->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(riic->clk)) {
	dev_err(&pdev->dev, "missing controller clock");
	return PTR_ERR(riic->clk);
	}

	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
	res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
	if (!res)
	return -ENODEV;

	ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
	0, riic_irqs[i].name, riic);
	if (ret) {
	dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
	return ret;
	}
	}

	adap = &riic->adapter;
	i2c_set_adapdata(adap, riic);
	strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
	adap->owner = THIS_MODULE;
	adap->algo = &riic_algo;
	adap->dev.parent = &pdev->dev;
	adap->dev.of_node = pdev->dev.of_node;

	init_completion(&riic->msg_done);

	i2c_parse_fw_timings(&pdev->dev, &i2c_t, true);

	ret = riic_init_hw(riic, &i2c_t);
	if (ret)
	return ret;


	ret = i2c_add_adapter(adap);
	if (ret)
	return ret;

	platform_set_drvdata(pdev, riic);

	dev_info(&pdev->dev, "registered with %dHz bus speed\n",
	i2c_t.bus_freq_hz);
	return 0;
	}

	static int riic_i2c_remove(struct platform_device *pdev)
	{
	struct riic_dev *riic = platform_get_drvdata(pdev);

	writeb(0, riic->base + RIIC_ICIER);
	i2c_del_adapter(&riic->adapter);

	return 0;
	}

	static const struct of_device_id riic_i2c_dt_ids[] = {
	{ .compatible = "renesas,riic-rz" },
	{ /* Sentinel */ },
	};

	static struct platform_driver riic_i2c_driver = {
	.probe = riic_i2c_probe,
	.remove = riic_i2c_remove,
	.driver = {
	.name = "i2c-riic",
	.of_match_table = riic_i2c_dt_ids,
	},
	};

	module_platform_driver(riic_i2c_driver);

	MODULE_DESCRIPTION("Renesas RIIC adapter");
	MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
	MODULE_LICENSE("GPL v2");
	MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);