i2c: rzg2l: Add I2C driver for RZ/G2L family

This driver supports the I2C module on the Renesas RZ/G2L (R9A07G044)
SoC, also known as the RIIC module.

This patch is based on both the u-boot driver in the Renesas RZ BSP
3.0.5 release [1] (commit 7fcc1fdc2534), and the Linux v6.7 driver
(commit 0dd3ee311255).

Support for deblocking the I2C bus is included as this may be needed
after triggering a reset via the Power Management IC (PMIC) over I2C
(the PMIC asserts the reset line before the SoC completes the I2C write
transaction with obvious bus locking effects). If the SDA line is
observed to be low during initialisation, we automatically attempt to
deblock.

[1]: https://github.com/renesas-rz/renesas-u-boot-cip

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

5 files changed, 635 insertions, 0 deletions

diff --git a/arch/arm/mach-rmobile/Kconfig b/arch/arm/mach-rmobile/Kconfig
index 2bb9674..38ede6e 100644
--- a/arch/arm/mach-rmobile/Kconfig
+++ b/arch/arm/mach-rmobile/Kconfig
@@ -78,6 +78,7 @@ config RZG2L
 	imply RENESAS_SDHI
 	imply RZG2L_GPIO
 	imply SCIF_CONSOLE
+	imply SYS_I2C_RZ_RIIC
 	imply SYS_MALLOC_F
 	help
 	  Enable support for the Renesas RZ/G2L family of SoCs. Currently
diff --git a/configs/renesas_rzg2l_smarc_defconfig b/configs/renesas_rzg2l_smarc_defconfig
index e45579a..ad46297 100644
--- a/configs/renesas_rzg2l_smarc_defconfig
+++ b/configs/renesas_rzg2l_smarc_defconfig
@@ -24,6 +24,7 @@ CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_CLK=y
 CONFIG_CMD_GPIO=y
+CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_PART=y
 CONFIG_CMD_EXT2=y
@@ -44,6 +45,7 @@ CONFIG_CLK=y
 CONFIG_CLK_RENESAS=y
 # CONFIG_CLK_RCAR_GEN3 is not set
 CONFIG_GPIO_HOG=y
+CONFIG_DM_I2C=y
 CONFIG_MMC_IO_VOLTAGE=y
 CONFIG_MMC_UHS_SUPPORT=y
 CONFIG_MMC_HS400_SUPPORT=y
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 4f42200..d2a3a13 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -524,6 +524,13 @@ config SYS_I2C_ROCKCHIP
 	  have several I2C ports and all are provided, controlled by the
 	  device tree.
 
+config SYS_I2C_RZ_RIIC
+	bool "Renesas RZ/G2L RIIC driver"
+	depends on RZG2L && DM_I2C
+	help
+	  Support for the I2C controller (RIIC) on the Renesas RZ/G2L SoC
+	  family.
+
 config SYS_I2C_SANDBOX
 	bool "Sandbox I2C driver"
 	depends on SANDBOX && DM_I2C
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index a96a8c7..692f63b 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_SYS_I2C_QUP) += qup_i2c.o
 obj-$(CONFIG_SYS_I2C_RCAR_I2C) += rcar_i2c.o
 obj-$(CONFIG_SYS_I2C_RCAR_IIC) += rcar_iic.o
 obj-$(CONFIG_SYS_I2C_ROCKCHIP) += rk_i2c.o
+obj-$(CONFIG_SYS_I2C_RZ_RIIC) += rz_riic.o
 obj-$(CONFIG_SYS_I2C_S3C24X0) += s3c24x0_i2c.o exynos_hs_i2c.o
 obj-$(CONFIG_SYS_I2C_SANDBOX) += sandbox_i2c.o i2c-emul-uclass.o
 obj-$(CONFIG_SYS_I2C_SH) += sh_i2c.o
diff --git a/drivers/i2c/rz_riic.c b/drivers/i2c/rz_riic.c
new file mode 100644
index 0000000..5f3f8d1
--- /dev/null
+++ b/drivers/i2c/rz_riic.c
@@ -0,0 +1,624 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * RZ/G2L I2C (RIIC) driver
+ *
+ * Copyright (C) 2021-2023 Renesas Electronics Corp.
+ */
+
+#include <asm/io.h>
+#include <clk.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <errno.h>
+#include <i2c.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <reset.h>
+#include <wait_bit.h>
+
+#define RIIC_ICCR1	0x00
+#define RIIC_ICCR2	0x04
+#define RIIC_ICMR1	0x08
+#define RIIC_ICMR2	0x0c
+#define RIIC_ICMR3	0x10
+#define RIIC_ICFER	0x14
+#define RIIC_ICSER	0x18
+#define RIIC_ICIER	0x1c
+#define RIIC_ICSR1	0x20
+#define RIIC_ICSR2	0x24
+#define RIIC_ICSAR0	0x28
+#define RIIC_ICBRL	0x34
+#define RIIC_ICBRH	0x38
+#define RIIC_ICDRT	0x3c
+#define RIIC_ICDRR	0x40
+
+/* ICCR1 */
+#define ICCR1_ICE	BIT(7)
+#define ICCR1_IICRST	BIT(6)
+#define ICCR1_CLO	BIT(5)
+#define ICCR1_SOWP	BIT(4)
+#define ICCR1_SCLO	BIT(3)
+#define ICCR1_SDAO	BIT(2)
+#define ICCR1_SCLI	BIT(1)
+#define ICCR1_SDAI	BIT(0)
+
+/* ICCR2 */
+#define ICCR2_BBSY	BIT(7)
+#define ICCR2_MST	BIT(6)
+#define ICCR2_TRS	BIT(5)
+#define ICCR2_SP	BIT(3)
+#define ICCR2_RS	BIT(2)
+#define ICCR2_ST	BIT(1)
+
+/* ICMR1 */
+#define ICMR1_MTWP	BIT(7)
+#define ICMR1_CKS_MASK	GENMASK(6, 4)
+#define ICMR1_BCWP	BIT(3)
+#define ICMR1_BC_MASK	GENMASK(2, 0)
+
+#define ICMR1_CKS(x)	(((x) << 4) & ICMR1_CKS_MASK)
+#define ICMR1_BC(x)	((x) & ICMR1_BC_MASK)
+
+/* ICMR2 */
+#define ICMR2_DLCS	BIT(7)
+#define ICMR2_SDDL_MASK	GENMASK(6, 4)
+#define ICMR2_TMOH	BIT(2)
+#define ICMR2_TMOL	BIT(1)
+#define ICMR2_TMOS	BIT(0)
+
+/* ICMR3 */
+#define ICMR3_SMBS	BIT(7)
+#define ICMR3_WAIT	BIT(6)
+#define ICMR3_RDRFS	BIT(5)
+#define ICMR3_ACKWP	BIT(4)
+#define ICMR3_ACKBT	BIT(3)
+#define ICMR3_ACKBR	BIT(2)
+#define ICMR3_NF_MASK	GENMASK(1, 0)
+
+/* ICFER */
+#define ICFER_FMPE	BIT(7)
+#define ICFER_SCLE	BIT(6)
+#define ICFER_NFE	BIT(5)
+#define ICFER_NACKE	BIT(4)
+#define ICFER_SALE	BIT(3)
+#define ICFER_NALE	BIT(2)
+#define ICFER_MALE	BIT(1)
+#define ICFER_TMOE	BIT(0)
+
+/* ICSER */
+#define ICSER_HOAE	BIT(7)
+#define ICSER_DIDE	BIT(5)
+#define ICSER_GCAE	BIT(3)
+#define ICSER_SAR2E	BIT(2)
+#define ICSER_SAR1E	BIT(1)
+#define ICSER_SAR0E	BIT(0)
+
+/* ICIER */
+#define ICIER_TIE	BIT(7)
+#define ICIER_TEIE	BIT(6)
+#define ICIER_RIE	BIT(5)
+#define ICIER_NAKIE	BIT(4)
+#define ICIER_SPIE	BIT(3)
+#define ICIER_STIE	BIT(2)
+#define ICIER_ALIE	BIT(1)
+#define ICIER_TMOIE	BIT(0)
+
+/* ICSR1 */
+#define ICSR1_HOA	BIT(7)
+#define ICSR1_DID	BIT(5)
+#define ICSR1_GCA	BIT(3)
+#define ICSR1_AAS2	BIT(2)
+#define ICSR1_AAS1	BIT(1)
+#define ICSR1_AAS0	BIT(0)
+
+/* ICSR2 */
+#define ICSR2_TDRE	BIT(7)
+#define ICSR2_TEND	BIT(6)
+#define ICSR2_RDRF	BIT(5)
+#define ICSR2_NACKF	BIT(4)
+#define ICSR2_STOP	BIT(3)
+#define ICSR2_START	BIT(2)
+#define ICSR2_AL	BIT(1)
+#define ICSR2_TMOF	BIT(0)
+
+/* ICBRH */
+#define ICBRH_RESERVED	GENMASK(7, 5)	/* The write value should always be 1 */
+#define ICBRH_BRH_MASK	GENMASK(4, 0)
+
+/* ICBRL */
+#define ICBRL_RESERVED	GENMASK(7, 5)	/* The write value should always be 1 */
+#define ICBRL_BRL_MASK	GENMASK(4, 0)
+
+#define RIIC_TIMEOUT_MSEC	100
+
+#define RIIC_FLAG_DEFAULT_SCL_RISE_TIME		BIT(0)
+#define RIIC_FLAG_DEFAULT_SCL_FALL_TIME		BIT(1)
+
+/*
+ * If SDA is stuck in a low state, the I2C spec says up to 9 clock cycles on SCL
+ * may be needed to unblock whichever other device on the bus is holding SDA low.
+ */
+#define I2C_DEBLOCK_MAX_CYCLES 9
+
+struct riic_priv {
+	void __iomem *base;
+	struct clk clk;
+	uint bus_speed;
+	u32 scl_rise_ns;
+	u32 scl_fall_ns;
+	u32 flags;
+};
+
+static int riic_check_busy(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = wait_for_bit_8(priv->base + RIIC_ICCR2, ICCR2_BBSY, 0,
+			     RIIC_TIMEOUT_MSEC, 0);
+	if (ret == -ETIMEDOUT) {
+		dev_dbg(dev, "bus is busy!\n");
+		return -EBUSY;
+	}
+
+	return ret;
+}
+
+static int riic_wait_for_icsr2(struct udevice *dev, u8 bit)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	ulong start = get_timer(0);
+	u8 icsr2;
+
+	/* We can't use wait_for_bit_8() here as we need to check for NACK. */
+	while (!((icsr2 = readb(priv->base + RIIC_ICSR2)) & bit)) {
+		if (icsr2 & ICSR2_NACKF)
+			return -EIO;
+		if (get_timer(start) > RIIC_TIMEOUT_MSEC) {
+			dev_dbg(dev, "timeout! (bit=%x, icsr2=%x, iccr2=%x)\n",
+				bit, icsr2, readb(priv->base + RIIC_ICCR2));
+			return -ETIMEDOUT;
+		}
+		udelay(1);
+		schedule();
+	}
+
+	return 0;
+}
+
+static int riic_check_nack_receive(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+
+	if (readb(priv->base + RIIC_ICSR2) & ICSR2_NACKF) {
+		dev_dbg(dev, "received nack!\n");
+		/* received NACK */
+		clrbits_8(priv->base + RIIC_ICSR2, ICSR2_NACKF);
+		setbits_8(priv->base + RIIC_ICCR2, ICCR2_SP);
+		readb(priv->base + RIIC_ICDRR);	/* dummy read */
+		return -EIO;
+	}
+	return 0;
+}
+
+static int riic_i2c_raw_write(struct udevice *dev, u8 *buf, size_t len)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	size_t i;
+	int ret;
+
+	for (i = 0; i < len; i++) {
+		ret = riic_check_nack_receive(dev);
+		if (ret < 0)
+			return ret;
+
+		ret = riic_wait_for_icsr2(dev, ICSR2_TDRE);
+		if (ret < 0)
+			return ret;
+
+		writeb(buf[i], priv->base + RIIC_ICDRT);
+	}
+
+	return riic_check_nack_receive(dev);
+}
+
+static int riic_send_start_cond(struct udevice *dev, int restart)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	if (restart)
+		setbits_8(priv->base + RIIC_ICCR2, ICCR2_RS);
+	else
+		setbits_8(priv->base + RIIC_ICCR2, ICCR2_ST);
+
+	ret = riic_wait_for_icsr2(dev, ICSR2_START);
+	if (ret < 0)
+		return ret;
+	clrbits_8(priv->base + RIIC_ICSR2, ICSR2_START);
+
+	return ret;
+}
+
+static int riic_receive_data(struct udevice *dev, struct i2c_msg *msg)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int ret, stop_ret, i;
+
+	ret = riic_wait_for_icsr2(dev, ICSR2_RDRF);
+	if (ret < 0)
+		goto send_stop;
+
+	ret = riic_check_nack_receive(dev);
+	if (ret < 0)
+		goto send_stop;
+
+	setbits_8(priv->base + RIIC_ICMR3, ICMR3_WAIT | ICMR3_ACKWP | ICMR3_RDRFS);
+
+	/* A dummy read must be performed to trigger data reception */
+	readb(priv->base + RIIC_ICDRR);
+
+	for (i = 0; i < msg->len; i++) {
+		ret = riic_wait_for_icsr2(dev, ICSR2_RDRF);
+		if (ret < 0)
+			goto send_stop;
+
+		if (i == (msg->len - 1)) {
+			clrbits_8(priv->base + RIIC_ICSR2, ICSR2_STOP);
+			setbits_8(priv->base + RIIC_ICCR2, ICCR2_SP);
+			setbits_8(priv->base + RIIC_ICMR3, ICMR3_ACKBT);
+		} else {
+			clrbits_8(priv->base + RIIC_ICMR3, ICMR3_ACKBT);
+		}
+
+		msg->buf[i] = readb(priv->base + RIIC_ICDRR);
+	};
+
+send_stop:
+	if (ret) {
+		/*
+		 * We got here due to an error condition, so we need to perform
+		 * a dummy read to issue the stop bit.
+		 */
+		clrbits_8(priv->base + RIIC_ICSR2, ICSR2_STOP);
+		setbits_8(priv->base + RIIC_ICCR2, ICCR2_SP);
+		readb(priv->base + RIIC_ICDRR);
+	}
+	stop_ret = riic_wait_for_icsr2(dev, ICSR2_STOP);
+	clrbits_8(priv->base + RIIC_ICSR2, ICSR2_STOP | ICSR2_NACKF);
+	clrbits_8(priv->base + RIIC_ICMR3, ICMR3_WAIT | ICMR3_ACKWP | ICMR3_RDRFS);
+	return ret ? ret : stop_ret;
+}
+
+static int riic_transmit_stop(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	clrbits_8(priv->base + RIIC_ICSR2, ICSR2_STOP);
+	setbits_8(priv->base + RIIC_ICCR2, ICCR2_SP);
+
+	ret = riic_wait_for_icsr2(dev, ICSR2_STOP);
+	clrbits_8(priv->base + RIIC_ICSR2, ICSR2_STOP | ICSR2_NACKF);
+	return ret;
+}
+
+static int riic_transmit_data(struct udevice *dev, struct i2c_msg *msg)
+{
+	int ret, stop_ret;
+
+	ret = riic_i2c_raw_write(dev, msg->buf, msg->len);
+	if (ret < 0)
+		goto send_stop;
+
+	ret = riic_wait_for_icsr2(dev, ICSR2_TEND);
+	if (ret < 0)
+		goto send_stop;
+
+	if (!ret && !(msg->flags & I2C_M_STOP))
+		return 0;
+
+send_stop:
+	stop_ret = riic_transmit_stop(dev);
+	return ret ? ret : stop_ret;
+}
+
+static int riic_xfer_one(struct udevice *dev, struct i2c_msg *msg, int first_msg)
+{
+	u8 addr_byte = ((msg->addr << 1) | (msg->flags & I2C_M_RD));
+	int ret;
+
+	if (!(msg->flags & I2C_M_NOSTART)) {
+		/*
+		 * Send a start for the first message and a restart for
+		 * subsequent messages.
+		 */
+		ret = riic_send_start_cond(dev, !first_msg);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = riic_i2c_raw_write(dev, &addr_byte, 1);
+	if (ret < 0) {
+		/*
+		 * We're aborting the transfer while still in master transmit
+		 * mode.
+		 */
+		riic_transmit_stop(dev);
+		return ret;
+	}
+
+	if (msg->flags & I2C_M_RD)
+		return riic_receive_data(dev, msg);
+
+	return riic_transmit_data(dev, msg);
+}
+
+static int riic_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
+{
+	int ret, i;
+
+	ret = riic_check_busy(dev);
+	if (ret < 0)
+		return ret;
+
+	/* Ensure that the last message is terminated with a stop bit. */
+	msg[nmsgs - 1].flags |= I2C_M_STOP;
+
+	for (i = 0; i < nmsgs; i++) {
+		ret = riic_xfer_one(dev, &msg[i], !i);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int riic_deblock(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int i = 0;
+
+	/*
+	 * Issue clock cycles on SCL to hopefully unblock whatever is holding
+	 * SDA low. These clock cycles may trigger error conditions such as
+	 * Arbitration Lost, so we clear the status bits in ICSR2 after each
+	 * cycle.
+	 */
+	while (!(readb(priv->base + RIIC_ICCR1) & ICCR1_SDAI)) {
+		if (i++ == I2C_DEBLOCK_MAX_CYCLES)
+			return -EIO;
+
+		setbits_8(priv->base + RIIC_ICCR1, ICCR1_CLO);
+		if (wait_for_bit_8(priv->base + RIIC_ICCR1, ICCR1_CLO, 0,
+				   RIIC_TIMEOUT_MSEC, false))
+			return -ETIMEDOUT;
+		writeb(0, priv->base + RIIC_ICSR2);
+	}
+
+	/*
+	 * We have released SDA, but the I2C module is now out of sync
+	 * with the bus state, so we need to reset its state machine.
+	 */
+	setbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+	clrbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+
+	return 0;
+}
+
+static int riic_set_bus_speed(struct udevice *dev, uint bus_speed)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	ulong refclk;
+	uint total_ticks, cks, brl, brh;
+
+	if (bus_speed > I2C_SPEED_FAST_PLUS_RATE) {
+		dev_err(dev, "unsupported bus speed (%dHz). %d max\n", bus_speed,
+			I2C_SPEED_FAST_PLUS_RATE);
+		return -EINVAL;
+	}
+
+	/*
+	 * 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.
+	 */
+	refclk = clk_get_rate(&priv->clk);
+	total_ticks = DIV_ROUND_UP(refclk, bus_speed ?: 1);
+
+	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;
+		refclk /= 2;
+	}
+
+	if (brl > (0x1f + 3)) {
+		dev_err(dev, "invalid speed (%u). Too slow.\n", bus_speed);
+		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;
+	}
+
+	/*
+	 * If SCL rise and fall times weren't set in the device tree, set them
+	 * based on the desired bus speed and the maximum timings given in the
+	 * I2C specification.
+	 */
+	if (priv->flags & RIIC_FLAG_DEFAULT_SCL_RISE_TIME)
+		priv->scl_rise_ns = bus_speed <= I2C_SPEED_STANDARD_RATE ? 1000 :
+				    bus_speed <= I2C_SPEED_FAST_RATE ? 300 : 120;
+	if (priv->flags & RIIC_FLAG_DEFAULT_SCL_FALL_TIME)
+		priv->scl_fall_ns = bus_speed <= I2C_SPEED_FAST_RATE ? 300 : 120;
+
+	/*
+	 * Remove clock ticks for rise and fall times. Convert ns to clock
+	 * ticks.
+	 */
+	brl -= priv->scl_fall_ns / (1000000000 / refclk);
+	brh -= priv->scl_rise_ns / (1000000000 / refclk);
+
+	/* Adjust for min register values for when SCLE=1 and NFE=1 */
+	if (brl < 1)
+		brl = 1;
+	if (brh < 1)
+		brh = 1;
+
+	priv->bus_speed = refclk / total_ticks;
+	dev_dbg(dev, "freq=%u, duty=%d, fall=%lu, rise=%lu, cks=%d, brl=%d, brh=%d\n",
+		priv->bus_speed, ((brl + 3) * 100) / (brl + brh + 6),
+		priv->scl_fall_ns / (1000000000 / refclk),
+		priv->scl_rise_ns / (1000000000 / refclk), cks, brl, brh);
+
+	setbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+	writeb(ICMR1_CKS(cks), priv->base + RIIC_ICMR1);
+	writeb(brh | ICBRH_RESERVED, priv->base + RIIC_ICBRH);
+	writeb(brl | ICBRL_RESERVED, priv->base + RIIC_ICBRL);
+	clrbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+
+	return 0;
+}
+
+static int riic_get_bus_speed(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+
+	return priv->bus_speed;
+}
+
+static const struct dm_i2c_ops riic_ops = {
+	.xfer           = riic_xfer,
+	.deblock        = riic_deblock,
+	.set_bus_speed	= riic_set_bus_speed,
+	.get_bus_speed	= riic_get_bus_speed,
+};
+
+static int riic_init_setting(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	clrbits_8(priv->base + RIIC_ICCR1, ICCR1_ICE);
+	setbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+	setbits_8(priv->base + RIIC_ICCR1, ICCR1_ICE);
+
+	/*
+	 * Set a default bitrate. The rate may be overridden based on the device
+	 * tree as part of i2c_post_probe().
+	 */
+	ret = riic_set_bus_speed(dev, I2C_SPEED_STANDARD_RATE);
+	if (ret < 0)
+		goto err;
+
+	clrbits_8(priv->base + RIIC_ICCR1, ICCR1_IICRST);
+
+	/* Make sure the bus is not stuck. */
+	if (!(readb(priv->base + RIIC_ICCR1) & ICCR1_SDAI)) {
+		dev_dbg(dev, "clearing SDA low state\n");
+		ret = riic_deblock(dev);
+		if (ret) {
+			dev_err(dev, "failed to clear SDA low state!\n");
+			goto err;
+		}
+	}
+	return 0;
+
+err:
+	clrbits_8(priv->base + RIIC_ICCR1, ICCR1_ICE | ICCR1_IICRST);
+	return ret;
+}
+
+static int riic_probe(struct udevice *dev)
+{
+	struct riic_priv *priv = dev_get_priv(dev);
+	struct reset_ctl rst;
+	int ret;
+
+	priv->base = dev_read_addr_ptr(dev);
+
+	ret = dev_read_u32(dev, "i2c-scl-rising-time-ns", &priv->scl_rise_ns);
+	if (ret)
+		priv->flags |= RIIC_FLAG_DEFAULT_SCL_RISE_TIME;
+	ret = dev_read_u32(dev, "i2c-scl-falling-time-ns", &priv->scl_fall_ns);
+	if (ret)
+		priv->flags |= RIIC_FLAG_DEFAULT_SCL_FALL_TIME;
+
+	ret = clk_get_by_index(dev, 0, &priv->clk);
+	if (ret) {
+		dev_err(dev, "failed to get clock\n");
+		return ret;
+	}
+
+	ret = clk_enable(&priv->clk);
+	if (ret) {
+		dev_err(dev, "failed to enable clock\n");
+		return ret;
+	}
+
+	ret = reset_get_by_index(dev, 0, &rst);
+	if (ret < 0) {
+		dev_err(dev, "failed to get reset line\n");
+		goto err_get_reset;
+	}
+
+	ret = reset_deassert(&rst);
+	if (ret < 0) {
+		dev_err(dev, "failed to de-assert reset line\n");
+		goto err_reset;
+	}
+
+	ret = riic_init_setting(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to init i2c bus interface\n");
+		goto err_init;
+	}
+
+	return 0;
+
+err_init:
+	reset_assert(&rst);
+err_reset:
+	reset_free(&rst);
+err_get_reset:
+	clk_disable(&priv->clk);
+	return ret;
+}
+
+static const struct udevice_id riic_ids[] = {
+	{ .compatible = "renesas,riic-rz", },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(riic_i2c) = {
+	.name           = "riic-i2c",
+	.id             = UCLASS_I2C,
+	.of_match       = riic_ids,
+	.probe          = riic_probe,
+	.priv_auto	= sizeof(struct riic_priv),
+	.ops            = &riic_ops,
+};