I2C: mediatek: Add driver for MediaTek I2C controller

The mediatek SoCs have I2C controller that handle I2C transfer.
This patch include common I2C bus driver.
This driver is compatible with I2C controller on mt65xx/mt81xx.
Signed-off-by: NXudong Chen <xudong.chen@mediatek.com>
Signed-off-by: NLiguo Zhang <liguo.zhang@mediatek.com>
Signed-off-by: NEddie Huang <eddie.huang@mediatek.com>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-mt6577.txt

+* Mediatek's I2C controller
+
+The Mediatek's I2C controller is used to interface with I2C devices.
+
+Required properties:
+  - compatible: value should be either of the following.
+      (a) "mediatek,mt6577-i2c", for i2c compatible with mt6577 i2c.
+      (b) "mediatek,mt6589-i2c", for i2c compatible with mt6589 i2c.
+      (c) "mediatek,mt8127-i2c", for i2c compatible with mt8127 i2c.
+      (d) "mediatek,mt8135-i2c", for i2c compatible with mt8135 i2c.
+      (e) "mediatek,mt8173-i2c", for i2c compatible with mt8173 i2c.
+  - reg: physical base address of the controller and dma base, length of memory
+    mapped region.
+  - interrupts: interrupt number to the cpu.
+  - clock-div: the fixed value for frequency divider of clock source in i2c
+    module. Each IC may be different.
+  - clocks: clock name from clock manager
+  - clock-names: Must include "main" and "dma", if enable have-pmic need include
+    "pmic" extra.
+
+Optional properties:
+  - clock-frequency: Frequency in Hz of the bus when transfer, the default value
+    is 100000.
+  - mediatek,have-pmic: platform can control i2c form special pmic side.
+    Only mt6589 and mt8135 support this feature.
+  - mediatek,use-push-pull: IO config use push-pull mode.
+
+Example:
+
+	i2c0: i2c@1100d000 {
+			compatible = "mediatek,mt6577-i2c";
+			reg = <0x1100d000 0x70>,
+			      <0x11000300 0x80>;
+			interrupts = <GIC_SPI 44 IRQ_TYPE_LEVEL_LOW>;
+			clock-frequency = <400000>;
+			mediatek,have-pmic;
+			clock-div = <16>;
+			clocks = <&i2c0_ck>, <&ap_dma_ck>;
+			clock-names = "main", "dma";
+	};
+

drivers/i2c/busses/Kconfig

@@ -620,6 +620,15 @@ config I2C_MPC
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mpc.
 
+config I2C_MT65XX
+	tristate "MediaTek I2C adapter"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	help
+	  This selects the MediaTek(R) Integrated Inter Circuit bus driver
+	  for MT65xx and MT81xx.
+	  If you want to use MediaTek(R) I2C interface, say Y or M here.
+	  If unsure, say N.
+
 config I2C_MV64XXX
 	tristate "Marvell mv64xxx I2C Controller"
 	depends on MV64X60 || PLAT_ORION || ARCH_SUNXI

drivers/i2c/busses/Makefile

@@ -60,6 +60,7 @@ obj-$(CONFIG_I2C_JZ4780)	+= i2c-jz4780.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
 obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
+obj-$(CONFIG_I2C_MT65XX)	+= i2c-mt65xx.o
 obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
 obj-$(CONFIG_I2C_NOMADIK)	+= i2c-nomadik.o

drivers/i2c/busses/i2c-mt65xx.c

+/*
+ * Copyright (c) 2014 MediaTek Inc.
+ * Author: Xudong Chen <xudong.chen@mediatek.com>
+ *
+ * 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 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/completion.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/scatterlist.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#define I2C_HS_NACKERR			(1 << 2)
+#define I2C_ACKERR			(1 << 1)
+#define I2C_TRANSAC_COMP		(1 << 0)
+#define I2C_TRANSAC_START		(1 << 0)
+#define I2C_DCM_DISABLE			0x0000
+#define I2C_IO_CONFIG_OPEN_DRAIN	0x0003
+#define I2C_IO_CONFIG_PUSH_PULL		0x0000
+#define I2C_SOFT_RST			0x0001
+#define I2C_FIFO_ADDR_CLR		0x0001
+#define I2C_DELAY_LEN			0x0002
+#define I2C_ST_START_CON		0x8001
+#define I2C_FS_START_CON		0x1800
+#define I2C_TIME_CLR_VALUE		0x0000
+#define I2C_TIME_DEFAULT_VALUE		0x0003
+#define I2C_FS_TIME_INIT_VALUE		0x1303
+#define I2C_WRRD_TRANAC_VALUE		0x0002
+#define I2C_RD_TRANAC_VALUE		0x0001
+
+#define I2C_DMA_CON_TX			0x0000
+#define I2C_DMA_CON_RX			0x0001
+#define I2C_DMA_START_EN		0x0001
+#define I2C_DMA_INT_FLAG_NONE		0x0000
+#define I2C_DMA_CLR_FLAG		0x0000
+
+#define I2C_DEFAULT_SPEED		100000	/* hz */
+#define MAX_FS_MODE_SPEED		400000
+#define MAX_HS_MODE_SPEED		3400000
+#define MAX_SAMPLE_CNT_DIV		8
+#define MAX_STEP_CNT_DIV		64
+#define MAX_HS_STEP_CNT_DIV		8
+
+#define I2C_CONTROL_RS                  (0x1 << 1)
+#define I2C_CONTROL_DMA_EN              (0x1 << 2)
+#define I2C_CONTROL_CLK_EXT_EN          (0x1 << 3)
+#define I2C_CONTROL_DIR_CHANGE          (0x1 << 4)
+#define I2C_CONTROL_ACKERR_DET_EN       (0x1 << 5)
+#define I2C_CONTROL_TRANSFER_LEN_CHANGE (0x1 << 6)
+#define I2C_CONTROL_WRAPPER             (0x1 << 0)
+
+#define I2C_DRV_NAME		"i2c-mt65xx"
+
+enum DMA_REGS_OFFSET {
+	OFFSET_INT_FLAG = 0x0,
+	OFFSET_INT_EN = 0x04,
+	OFFSET_EN = 0x08,
+	OFFSET_CON = 0x18,
+	OFFSET_TX_MEM_ADDR = 0x1c,
+	OFFSET_RX_MEM_ADDR = 0x20,
+	OFFSET_TX_LEN = 0x24,
+	OFFSET_RX_LEN = 0x28,
+};
+
+enum i2c_trans_st_rs {
+	I2C_TRANS_STOP = 0,
+	I2C_TRANS_REPEATED_START,
+};
+
+enum mtk_trans_op {
+	I2C_MASTER_WR = 1,
+	I2C_MASTER_RD,
+	I2C_MASTER_WRRD,
+};
+
+enum I2C_REGS_OFFSET {
+	OFFSET_DATA_PORT = 0x0,
+	OFFSET_SLAVE_ADDR = 0x04,
+	OFFSET_INTR_MASK = 0x08,
+	OFFSET_INTR_STAT = 0x0c,
+	OFFSET_CONTROL = 0x10,
+	OFFSET_TRANSFER_LEN = 0x14,
+	OFFSET_TRANSAC_LEN = 0x18,
+	OFFSET_DELAY_LEN = 0x1c,
+	OFFSET_TIMING = 0x20,
+	OFFSET_START = 0x24,
+	OFFSET_EXT_CONF = 0x28,
+	OFFSET_FIFO_STAT = 0x30,
+	OFFSET_FIFO_THRESH = 0x34,
+	OFFSET_FIFO_ADDR_CLR = 0x38,
+	OFFSET_IO_CONFIG = 0x40,
+	OFFSET_RSV_DEBUG = 0x44,
+	OFFSET_HS = 0x48,
+	OFFSET_SOFTRESET = 0x50,
+	OFFSET_DCM_EN = 0x54,
+	OFFSET_PATH_DIR = 0x60,
+	OFFSET_DEBUGSTAT = 0x64,
+	OFFSET_DEBUGCTRL = 0x68,
+	OFFSET_TRANSFER_LEN_AUX = 0x6c,
+};
+
+struct mtk_i2c_compatible {
+	const struct i2c_adapter_quirks *quirks;
+	unsigned char pmic_i2c: 1;
+	unsigned char dcm: 1;
+};
+
+struct mtk_i2c {
+	struct i2c_adapter adap;	/* i2c host adapter */
+	struct device *dev;
+	struct completion msg_complete;
+
+	/* set in i2c probe */
+	void __iomem *base;		/* i2c base addr */
+	void __iomem *pdmabase;		/* dma base address*/
+	struct clk *clk_main;		/* main clock for i2c bus */
+	struct clk *clk_dma;		/* DMA clock for i2c via DMA */
+	struct clk *clk_pmic;		/* PMIC clock for i2c from PMIC */
+	bool have_pmic;			/* can use i2c pins from PMIC */
+	bool use_push_pull;		/* IO config push-pull mode */
+
+	u16 irq_stat;			/* interrupt status */
+	unsigned int speed_hz;		/* The speed in transfer */
+	enum mtk_trans_op op;
+	u16 timing_reg;
+	u16 high_speed_reg;
+	const struct mtk_i2c_compatible *dev_comp;
+};
+
+static const struct i2c_adapter_quirks mt6577_i2c_quirks = {
+	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
+	.max_num_msgs = 1,
+	.max_write_len = 255,
+	.max_read_len = 255,
+	.max_comb_1st_msg_len = 255,
+	.max_comb_2nd_msg_len = 31,
+};
+
+static const struct mtk_i2c_compatible mt6577_compat = {
+	.quirks = &mt6577_i2c_quirks,
+	.pmic_i2c = 0,
+	.dcm = 1,
+};
+
+static const struct mtk_i2c_compatible mt6589_compat = {
+	.quirks = &mt6577_i2c_quirks,
+	.pmic_i2c = 1,
+	.dcm = 0,
+};
+
+static const struct of_device_id mtk_i2c_of_match[] = {
+	{ .compatible = "mediatek,mt6577-i2c", .data = &mt6577_compat },
+	{ .compatible = "mediatek,mt6589-i2c", .data = &mt6589_compat },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mtk_i2c_of_match);
+
+static int mtk_i2c_clock_enable(struct mtk_i2c *i2c)
+{
+	int ret;
+
+	ret = clk_prepare_enable(i2c->clk_dma);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(i2c->clk_main);
+	if (ret)
+		goto err_main;
+
+	if (i2c->have_pmic) {
+		ret = clk_prepare_enable(i2c->clk_pmic);
+		if (ret)
+			goto err_pmic;
+	}
+	return 0;
+
+err_pmic:
+	clk_disable_unprepare(i2c->clk_main);
+err_main:
+	clk_disable_unprepare(i2c->clk_dma);
+
+	return ret;
+}
+
+static void mtk_i2c_clock_disable(struct mtk_i2c *i2c)
+{
+	if (i2c->have_pmic)
+		clk_disable_unprepare(i2c->clk_pmic);
+
+	clk_disable_unprepare(i2c->clk_main);
+	clk_disable_unprepare(i2c->clk_dma);
+}
+
+static void mtk_i2c_init_hw(struct mtk_i2c *i2c)
+{
+	u16 control_reg;
+
+	writew(I2C_SOFT_RST, i2c->base + OFFSET_SOFTRESET);
+
+	/* Set ioconfig */
+	if (i2c->use_push_pull)
+		writew(I2C_IO_CONFIG_PUSH_PULL, i2c->base + OFFSET_IO_CONFIG);
+	else
+		writew(I2C_IO_CONFIG_OPEN_DRAIN, i2c->base + OFFSET_IO_CONFIG);
+
+	if (i2c->dev_comp->dcm)
+		writew(I2C_DCM_DISABLE, i2c->base + OFFSET_DCM_EN);
+
+	writew(i2c->timing_reg, i2c->base + OFFSET_TIMING);
+	writew(i2c->high_speed_reg, i2c->base + OFFSET_HS);
+
+	/* If use i2c pin from PMIC mt6397 side, need set PATH_DIR first */
+	if (i2c->have_pmic)
+		writew(I2C_CONTROL_WRAPPER, i2c->base + OFFSET_PATH_DIR);
+
+	control_reg = I2C_CONTROL_ACKERR_DET_EN |
+		      I2C_CONTROL_CLK_EXT_EN | I2C_CONTROL_DMA_EN;
+	writew(control_reg, i2c->base + OFFSET_CONTROL);
+	writew(I2C_DELAY_LEN, i2c->base + OFFSET_DELAY_LEN);
+}
+
+/*
+ * Calculate i2c port speed
+ *
+ * Hardware design:
+ * i2c_bus_freq = parent_clk / (clock_div * 2 * sample_cnt * step_cnt)
+ * clock_div: fixed in hardware, but may be various in different SoCs
+ *
+ * The calculation want to pick the highest bus frequency that is still
+ * less than or equal to i2c->speed_hz. The calculation try to get
+ * sample_cnt and step_cn
+ */
+static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int parent_clk,
+			     unsigned int clock_div)
+{
+	unsigned int clk_src;
+	unsigned int step_cnt;
+	unsigned int sample_cnt;
+	unsigned int max_step_cnt;
+	unsigned int target_speed;
+	unsigned int base_sample_cnt = MAX_SAMPLE_CNT_DIV;
+	unsigned int base_step_cnt;
+	unsigned int opt_div;
+	unsigned int best_mul;
+	unsigned int cnt_mul;
+
+	clk_src = parent_clk / clock_div;
+	target_speed = i2c->speed_hz;
+
+	if (target_speed > MAX_HS_MODE_SPEED)
+		target_speed = MAX_HS_MODE_SPEED;
+
+	if (target_speed > MAX_FS_MODE_SPEED)
+		max_step_cnt = MAX_HS_STEP_CNT_DIV;
+	else
+		max_step_cnt = MAX_STEP_CNT_DIV;
+
+	base_step_cnt = max_step_cnt;
+	/* Find the best combination */
+	opt_div = DIV_ROUND_UP(clk_src >> 1, target_speed);
+	best_mul = MAX_SAMPLE_CNT_DIV * max_step_cnt;
+
+	/* Search for the best pair (sample_cnt, step_cnt) with
+	 * 0 < sample_cnt < MAX_SAMPLE_CNT_DIV
+	 * 0 < step_cnt < max_step_cnt
+	 * sample_cnt * step_cnt >= opt_div
+	 * optimizing for sample_cnt * step_cnt being minimal
+	 */
+	for (sample_cnt = 1; sample_cnt <= MAX_SAMPLE_CNT_DIV; sample_cnt++) {
+		step_cnt = DIV_ROUND_UP(opt_div, sample_cnt);
+		cnt_mul = step_cnt * sample_cnt;
+		if (step_cnt > max_step_cnt)
+			continue;
+
+		if (cnt_mul < best_mul) {
+			best_mul = cnt_mul;
+			base_sample_cnt = sample_cnt;
+			base_step_cnt = step_cnt;
+			if (best_mul == opt_div)
+				break;
+		}
+	}
+
+	sample_cnt = base_sample_cnt;
+	step_cnt = base_step_cnt;
+
+	if ((clk_src / (2 * sample_cnt * step_cnt)) > target_speed) {
+		/* In this case, hardware can't support such
+		 * low i2c_bus_freq
+		 */
+		dev_dbg(i2c->dev, "Unsupported speed (%uhz)\n",	target_speed);
+		return -EINVAL;
+	}
+
+	step_cnt--;
+	sample_cnt--;
+
+	if (target_speed > MAX_FS_MODE_SPEED) {
+		/* Set the high speed mode register */
+		i2c->timing_reg = I2C_FS_TIME_INIT_VALUE;
+		i2c->high_speed_reg = I2C_TIME_DEFAULT_VALUE |
+			(sample_cnt << 12) | (step_cnt << 8);
+	} else {
+		i2c->timing_reg = (sample_cnt << 8) | (step_cnt << 0);
+		/* Disable the high speed transaction */
+		i2c->high_speed_reg = I2C_TIME_CLR_VALUE;
+	}
+
+	return 0;
+}
+
+static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs)
+{
+	u16 addr_reg;
+	u16 control_reg;
+	dma_addr_t rpaddr = 0;
+	dma_addr_t wpaddr = 0;
+	int ret;
+
+	i2c->irq_stat = 0;
+
+	reinit_completion(&i2c->msg_complete);
+
+	control_reg = readw(i2c->base + OFFSET_CONTROL) &
+			~(I2C_CONTROL_DIR_CHANGE | I2C_CONTROL_RS);
+	if (i2c->speed_hz > 400000)
+		control_reg |= I2C_CONTROL_RS;
+
+	if (i2c->op == I2C_MASTER_WRRD)
+		control_reg |= I2C_CONTROL_DIR_CHANGE | I2C_CONTROL_RS;
+
+	writew(control_reg, i2c->base + OFFSET_CONTROL);
+
+	/* set start condition */
+	if (i2c->speed_hz <= 100000)
+		writew(I2C_ST_START_CON, i2c->base + OFFSET_EXT_CONF);
+	else
+		writew(I2C_FS_START_CON, i2c->base + OFFSET_EXT_CONF);
+
+	addr_reg = msgs->addr << 1;
+	if (i2c->op == I2C_MASTER_RD)
+		addr_reg |= 0x1;
+
+	writew(addr_reg, i2c->base + OFFSET_SLAVE_ADDR);
+
+	/* Clear interrupt status */
+	writew(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP,
+	       i2c->base + OFFSET_INTR_STAT);
+	writew(I2C_FIFO_ADDR_CLR, i2c->base + OFFSET_FIFO_ADDR_CLR);
+
+	/* Enable interrupt */
+	writew(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP,
+	       i2c->base + OFFSET_INTR_MASK);
+
+	/* Set transfer and transaction len */
+	if (i2c->op == I2C_MASTER_WRRD) {
+		writew(msgs->len | ((msgs + 1)->len) << 8,
+		       i2c->base + OFFSET_TRANSFER_LEN);
+		writew(I2C_WRRD_TRANAC_VALUE, i2c->base + OFFSET_TRANSAC_LEN);
+	} else {
+		writew(msgs->len, i2c->base + OFFSET_TRANSFER_LEN);
+		writew(I2C_RD_TRANAC_VALUE, i2c->base + OFFSET_TRANSAC_LEN);
+	}
+
+	/* Prepare buffer data to start transfer */
+	if (i2c->op == I2C_MASTER_RD) {
+		writel(I2C_DMA_INT_FLAG_NONE, i2c->pdmabase + OFFSET_INT_FLAG);
+		writel(I2C_DMA_CON_RX, i2c->pdmabase + OFFSET_CON);
+		rpaddr = dma_map_single(i2c->dev, msgs->buf,
+					msgs->len, DMA_FROM_DEVICE);
+		if (dma_mapping_error(i2c->dev, rpaddr))
+			return -ENOMEM;
+		writel((u32)rpaddr, i2c->pdmabase + OFFSET_RX_MEM_ADDR);
+		writel(msgs->len, i2c->pdmabase + OFFSET_RX_LEN);
+	} else if (i2c->op == I2C_MASTER_WR) {
+		writel(I2C_DMA_INT_FLAG_NONE, i2c->pdmabase + OFFSET_INT_FLAG);
+		writel(I2C_DMA_CON_TX, i2c->pdmabase + OFFSET_CON);
+		wpaddr = dma_map_single(i2c->dev, msgs->buf,
+					msgs->len, DMA_TO_DEVICE);
+		if (dma_mapping_error(i2c->dev, wpaddr))
+			return -ENOMEM;
+		writel((u32)wpaddr, i2c->pdmabase + OFFSET_TX_MEM_ADDR);
+		writel(msgs->len, i2c->pdmabase + OFFSET_TX_LEN);
+	} else {
+		writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_INT_FLAG);
+		writel(I2C_DMA_CLR_FLAG, i2c->pdmabase + OFFSET_CON);
+		wpaddr = dma_map_single(i2c->dev, msgs->buf,
+					msgs->len, DMA_TO_DEVICE);
+		if (dma_mapping_error(i2c->dev, wpaddr))
+			return -ENOMEM;
+		rpaddr = dma_map_single(i2c->dev, (msgs + 1)->buf,
+					(msgs + 1)->len,
+					DMA_FROM_DEVICE);
+		if (dma_mapping_error(i2c->dev, rpaddr)) {
+			dma_unmap_single(i2c->dev, wpaddr,
+					 msgs->len, DMA_TO_DEVICE);
+			return -ENOMEM;
+		}
+		writel((u32)wpaddr, i2c->pdmabase + OFFSET_TX_MEM_ADDR);
+		writel((u32)rpaddr, i2c->pdmabase + OFFSET_RX_MEM_ADDR);
+		writel(msgs->len, i2c->pdmabase + OFFSET_TX_LEN);
+		writel((msgs + 1)->len, i2c->pdmabase + OFFSET_RX_LEN);
+	}
+
+	writel(I2C_DMA_START_EN, i2c->pdmabase + OFFSET_EN);
+	writew(I2C_TRANSAC_START, i2c->base + OFFSET_START);
+
+	ret = wait_for_completion_timeout(&i2c->msg_complete,
+					  i2c->adap.timeout);
+
+	/* Clear interrupt mask */
+	writew(~(I2C_HS_NACKERR | I2C_ACKERR |
+	       I2C_TRANSAC_COMP), i2c->base + OFFSET_INTR_MASK);
+
+	if (i2c->op == I2C_MASTER_WR) {
+		dma_unmap_single(i2c->dev, wpaddr,
+				 msgs->len, DMA_TO_DEVICE);
+	} else if (i2c->op == I2C_MASTER_RD) {
+		dma_unmap_single(i2c->dev, rpaddr,
+				 msgs->len, DMA_FROM_DEVICE);
+	} else {
+		dma_unmap_single(i2c->dev, wpaddr, msgs->len,
+				 DMA_TO_DEVICE);
+		dma_unmap_single(i2c->dev, rpaddr, (msgs + 1)->len,
+				 DMA_FROM_DEVICE);
+	}
+
+	if (ret == 0) {
+		dev_dbg(i2c->dev, "addr: %x, transfer timeout\n", msgs->addr);
+		mtk_i2c_init_hw(i2c);
+		return -ETIMEDOUT;
+	}
+
+	completion_done(&i2c->msg_complete);
+
+	if (i2c->irq_stat & (I2C_HS_NACKERR | I2C_ACKERR)) {
+		dev_dbg(i2c->dev, "addr: %x, transfer ACK error\n", msgs->addr);
+		mtk_i2c_init_hw(i2c);
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+static int mtk_i2c_transfer(struct i2c_adapter *adap,
+			    struct i2c_msg msgs[], int num)
+{
+	int ret;
+	int left_num = num;
+	struct mtk_i2c *i2c = i2c_get_adapdata(adap);
+
+	ret = mtk_i2c_clock_enable(i2c);
+	if (ret)
+		return ret;
+
+	if (!msgs->buf) {
+		dev_dbg(i2c->dev, "data buffer is NULL.\n");
+		ret = -EINVAL;
+		goto err_exit;
+	}
+
+	if (msgs->flags & I2C_M_RD)
+		i2c->op = I2C_MASTER_RD;
+	else
+		i2c->op = I2C_MASTER_WR;
+
+	if (num > 1) {
+		/* combined two messages into one transaction */
+		i2c->op = I2C_MASTER_WRRD;
+		left_num--;
+	}
+
+	/* always use DMA mode. */
+	ret = mtk_i2c_do_transfer(i2c, msgs);
+	if (ret < 0)
+		goto err_exit;
+
+	/* the return value is number of executed messages */
+	ret = num;
+
+err_exit:
+	mtk_i2c_clock_disable(i2c);
+	return ret;
+}
+
+static irqreturn_t mtk_i2c_irq(int irqno, void *dev_id)
+{
+	struct mtk_i2c *i2c = dev_id;
+
+	i2c->irq_stat = readw(i2c->base + OFFSET_INTR_STAT);
+	writew(I2C_HS_NACKERR | I2C_ACKERR
+		| I2C_TRANSAC_COMP, i2c->base + OFFSET_INTR_STAT);
+
+	complete(&i2c->msg_complete);
+
+	return IRQ_HANDLED;
+}
+
+static u32 mtk_i2c_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm mtk_i2c_algorithm = {
+	.master_xfer = mtk_i2c_transfer,
+	.functionality = mtk_i2c_functionality,
+};
+
+static int mtk_i2c_parse_dt(struct device_node *np, struct mtk_i2c *i2c,
+			    unsigned int *clk_src_div)
+{
+	int ret;
+
+	ret = of_property_read_u32(np, "clock-frequency", &i2c->speed_hz);
+	if (ret < 0)
+		i2c->speed_hz = I2C_DEFAULT_SPEED;
+
+	ret = of_property_read_u32(np, "clock-div", clk_src_div);
+	if (ret < 0)
+		return ret;
+
+	if (*clk_src_div == 0)
+		return -EINVAL;
+
+	i2c->have_pmic = of_property_read_bool(np, "mediatek,have-pmic");
+	i2c->use_push_pull =
+		of_property_read_bool(np, "mediatek,use-push-pull");
+
+	return 0;
+}
+
+static int mtk_i2c_probe(struct platform_device *pdev)
+{
+	const struct of_device_id *of_id;
+	int ret = 0;
+	struct mtk_i2c *i2c;
+	struct clk *clk;
+	unsigned int clk_src_div;
+	struct resource *res;
+	int irq;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	ret = mtk_i2c_parse_dt(pdev->dev.of_node, i2c, &clk_src_div);
+	if (ret)
+		return -EINVAL;
+
+	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);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	i2c->pdmabase = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(i2c->pdmabase))
+		return PTR_ERR(i2c->pdmabase);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq <= 0)
+		return irq;
+
+	init_completion(&i2c->msg_complete);
+
+	of_id = of_match_node(mtk_i2c_of_match, pdev->dev.of_node);
+	if (!of_id)
+		return -EINVAL;
+
+	i2c->dev_comp = of_id->data;
+	i2c->adap.dev.of_node = pdev->dev.of_node;
+	i2c->dev = &pdev->dev;
+	i2c->adap.dev.parent = &pdev->dev;
+	i2c->adap.owner = THIS_MODULE;
+	i2c->adap.algo = &mtk_i2c_algorithm;
+	i2c->adap.quirks = i2c->dev_comp->quirks;
+	i2c->adap.timeout = 2 * HZ;
+	i2c->adap.retries = 1;
+
+	if (i2c->have_pmic && !i2c->dev_comp->pmic_i2c)
+		return -EINVAL;
+
+	i2c->clk_main = devm_clk_get(&pdev->dev, "main");
+	if (IS_ERR(i2c->clk_main)) {
+		dev_err(&pdev->dev, "cannot get main clock\n");
+		return PTR_ERR(i2c->clk_main);
+	}
+
+	i2c->clk_dma = devm_clk_get(&pdev->dev, "dma");
+	if (IS_ERR(i2c->clk_dma)) {
+		dev_err(&pdev->dev, "cannot get dma clock\n");
+		return PTR_ERR(i2c->clk_dma);
+	}
+
+	clk = i2c->clk_main;
+	if (i2c->have_pmic) {
+		i2c->clk_pmic = devm_clk_get(&pdev->dev, "pmic");
+		if (IS_ERR(i2c->clk_pmic)) {
+			dev_err(&pdev->dev, "cannot get pmic clock\n");
+			return PTR_ERR(i2c->clk_pmic);
+		}
+		clk = i2c->clk_pmic;
+	}
+
+	strlcpy(i2c->adap.name, I2C_DRV_NAME, sizeof(i2c->adap.name));
+
+	ret = mtk_i2c_set_speed(i2c, clk_get_rate(clk), clk_src_div);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to set the speed.\n");
+		return -EINVAL;
+	}
+
+	ret = mtk_i2c_clock_enable(i2c);
+	if (ret) {
+		dev_err(&pdev->dev, "clock enable failed!\n");
+		return ret;
+	}
+	mtk_i2c_init_hw(i2c);
+	mtk_i2c_clock_disable(i2c);
+
+	ret = devm_request_irq(&pdev->dev, irq, mtk_i2c_irq,
+			       IRQF_TRIGGER_NONE, I2C_DRV_NAME, i2c);
+	if (ret < 0) {
+		dev_err(&pdev->dev,
+			"Request I2C IRQ %d fail\n", irq);
+		return ret;
+	}
+
+	i2c_set_adapdata(&i2c->adap, i2c);
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to add i2c bus to i2c core\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, i2c);
+
+	return 0;
+}
+
+static int mtk_i2c_remove(struct platform_device *pdev)
+{
+	struct mtk_i2c *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adap);
+
+	return 0;
+}
+
+static struct platform_driver mtk_i2c_driver = {
+	.probe = mtk_i2c_probe,
+	.remove = mtk_i2c_remove,
+	.driver = {
+		.name = I2C_DRV_NAME,
+		.of_match_table = of_match_ptr(mtk_i2c_of_match),
+	},
+};
+
+module_platform_driver(mtk_i2c_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MediaTek I2C Bus Driver");
+MODULE_AUTHOR("Xudong Chen <xudong.chen@mediatek.com>");