Hi Naveen,

Looks mostly good, but see some comments inline.

On Wednesday 19 of June 2013 16:18:25 Naveen Krishna Chatradhi wrote:

IMHO this compatible value is too wide. You might end up with new Exynos 5 
SoC that has a high speed I2C controller as well, but slightly different, 
requiring some extra quirks.  Now exynos5 in compatible would suggest that 
it covers all Exynos 5 SoCs, but such SoC would require new one.

Basically, my suggestion is to use a compatible value with name of first SoC 
in which given IP appeared, as it is already done in most bindings.

I think a comment about mode used in this driver would be good.

+ * Special bits are available for both modes of operation to set
commands + * and for checking transfer status
+ */
+
+/* Register Map */
+#define HSI2C_CTL		0x00
+#define HSI2C_FIFO_CTL		0x04
+#define HSI2C_TRAILIG_CTL	0x08
+#define HSI2C_CLK_CTL		0x0C
+#define HSI2C_CLK_SLOT		0x10
+#define HSI2C_INT_ENABLE	0x20
+#define HSI2C_INT_STATUS	0x24
+#define HSI2C_ERR_STATUS	0x2C
+#define HSI2C_FIFO_STATUS	0x30
+#define HSI2C_TX_DATA		0x34
+#define HSI2C_RX_DATA		0x38
+#define HSI2C_CONF		0x40
+#define HSI2C_AUTO_CONF		0x44
+#define HSI2C_TIMEOUT		0x48
+#define HSI2C_MANUAL_CMD	0x4C
+#define HSI2C_TRANS_STATUS	0x50
+#define HSI2C_TIMING_HS1	0x54
+#define HSI2C_TIMING_HS2	0x58
+#define HSI2C_TIMING_HS3	0x5C
+#define HSI2C_TIMING_FS1	0x60
+#define HSI2C_TIMING_FS2	0x64
+#define HSI2C_TIMING_FS3	0x68
+#define HSI2C_TIMING_SLA	0x6C
+#define HSI2C_ADDR		0x70

nit: AFAIK lower case characters are preferred in hexadecimal numbers in 
kernel coding style.

+/* I2C_CTL Register bits */
+#define HSI2C_FUNC_MODE_I2C			(1u << 0)
+#define HSI2C_MASTER				(1u << 3)
+#define HSI2C_RXCHON				(1u << 6)
+#define HSI2C_TXCHON				(1u << 7)
+#define HSI2C_SW_RST				(1u << 31)
+
+/* I2C_FIFO_CTL Register bits */
+#define HSI2C_RXFIFO_EN				(1u << 0)
+#define HSI2C_TXFIFO_EN				(1u << 1)
+#define HSI2C_FIFO_MAX				(0x40)

nit: You don't need parentheses in case of simple numbers.

+#define HSI2C_RXFIFO_TRIGGER_LEVEL(x)		((x) << 4)
+#define HSI2C_TXFIFO_TRIGGER_LEVEL(x)		((x) << 16)
+/* I2C_TRAILING_CTL Register bits */
+#define HSI2C_TRAILING_COUNT			(0xf)
+
+/* I2C_INT_EN Register bits */
+#define HSI2C_INT_TX_ALMOSTEMPTY_EN		(1u << 0)
+#define HSI2C_INT_RX_ALMOSTFULL_EN		(1u << 1)
+#define HSI2C_INT_TRAILING_EN			(1u << 6)
+#define HSI2C_INT_I2C_EN			(1u << 9)
+
+/* I2C_INT_STAT Register bits */
+#define HSI2C_INT_TX_ALMOSTEMPTY		(1u << 0)
+#define HSI2C_INT_RX_ALMOSTFULL			(1u << 1)
+#define HSI2C_INT_TX_UNDERRUN			(1u << 2)
+#define HSI2C_INT_TX_OVERRUN			(1u << 3)
+#define HSI2C_INT_RX_UNDERRUN			(1u << 4)
+#define HSI2C_INT_RX_OVERRUN			(1u << 5)
+#define HSI2C_INT_TRAILING			(1u << 6)
+#define HSI2C_INT_I2C				(1u << 9)
+#define HSI2C_RX_INT				(HSI2C_INT_RX_ALMOSTFULL | \
+						 HSI2C_INT_RX_UNDERRUN | \
+						 HSI2C_INT_RX_OVERRUN | \
+						 HSI2C_INT_TRAILING)
+
+/* I2C_FIFO_STAT Register bits */
+#define HSI2C_RX_FIFO_EMPTY			(1u << 24)
+#define HSI2C_RX_FIFO_FULL			(1u << 23)
+#define HSI2C_RX_FIFO_LVL(x)			((x >> 16) & 0x7f)
+#define HSI2C_TX_FIFO_EMPTY			(1u << 8)
+#define HSI2C_TX_FIFO_FULL			(1u << 7)
+#define HSI2C_TX_FIFO_LVL(x)			((x >> 0) & 0x7f)
+#define HSI2C_FIFO_EMPTY			(HSI2C_RX_FIFO_EMPTY |	\
+						HSI2C_TX_FIFO_EMPTY)
+
+/* I2C_CONF Register bits */
+#define HSI2C_AUTO_MODE				(1u << 31)
+#define HSI2C_10BIT_ADDR_MODE			(1u << 30)
+#define HSI2C_HS_MODE				(1u << 29)
+
+/* I2C_AUTO_CONF Register bits */
+#define HSI2C_READ_WRITE			(1u << 16)
+#define HSI2C_STOP_AFTER_TRANS			(1u << 17)
+#define HSI2C_MASTER_RUN			(1u << 31)
+
+/* I2C_TIMEOUT Register bits */
+#define HSI2C_TIMEOUT_EN			(1u << 31)
+
+/* I2C_TRANS_STATUS register bits */
+#define HSI2C_MASTER_BUSY			(1u << 17)
+#define HSI2C_SLAVE_BUSY			(1u << 16)
+#define HSI2C_TIMEOUT_AUTO			(1u << 4)
+#define HSI2C_NO_DEV				(1u << 3)
+#define HSI2C_NO_DEV_ACK			(1u << 2)
+#define HSI2C_TRANS_ABORT			(1u << 1)
+#define HSI2C_TRANS_DONE			(1u << 0)
+
+/* I2C_ADDR register bits */
+#define HSI2C_SLV_ADDR_SLV(x)			((x & 0x3ff) << 0)
+#define HSI2C_SLV_ADDR_MAS(x)			((x & 0x3ff) << 10)
+#define HSI2C_MASTER_ID(x)			((x & 0xff) << 24)
+#define MASTER_ID(x)				((x & 0x7) + 0x08)
+
+/*
+ * Controller operating frequency, timing values for operation
+ * are calculated against this frequency
+ */
+#define HSI2C_HS_TX_CLOCK	1000000
+#define HSI2C_FS_TX_CLOCK	100000
+#define HSI2C_HIGH_SPD		1
+#define HSI2C_FAST_SPD		0
+
+#define EXYNOS5_I2C_TIMEOUT (msecs_to_jiffies(1000))
+
+/* timeout for pm runtime autosuspend */
+#define EXYNOS5_I2C_PM_TIMEOUT		1000	/* ms */

1 second seems a lot, but I guess such block don't use too much power.

+struct exynos5_i2c {
+	struct i2c_adapter	adap;
+	unsigned int		suspended:1;
+
+	struct i2c_msg		*msg;
+	struct completion	msg_complete;
+	unsigned int		msg_ptr;
+	unsigned int		msg_len;
+
+	unsigned int		irq;
+
+	void __iomem		*regs;
+	struct clk		*clk;
+	struct device		*dev;
+	int			state;
+
+	/*
+	 * Since the TRANS_DONE bit is cleared on read, and we may read it
+	 * either during an IRQ or after a transaction, keep track of its
+	 * state here.
+	 */
+	int			trans_done;
+
+	/* Controller operating frequency */
+	unsigned int		fs_clock;
+	unsigned int		hs_clock;
+
+	/*
+	 * HSI2C Controller can operate in
+	 * 1. High speed upto 3.4Mbps
+	 * 2. Fast speed upto 1Mbps
+	 */
+	int			speed_mode;
+	int			bus_id;
+};
+
+static const struct of_device_id exynos5_i2c_match[] = {
+	{ .compatible = "samsung,exynos5-hsi2c" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, exynos5_i2c_match);
+
+static void exynos5_i2c_clr_pend_irq(struct exynos5_i2c *i2c)
+{
+	writel(readl(i2c->regs + HSI2C_INT_STATUS),
+				i2c->regs + HSI2C_INT_STATUS);
+}
+
+/*
+ * exynos5_i2c_set_timing: updates the registers with appropriate
+ * timing values calculated
+ *
+ * Returns 0 on success, -EINVAL if the cycle length cannot
+ * be calculated.
+ */
+static int exynos5_i2c_set_timing(struct exynos5_i2c *i2c, int mode)
+{
+	u32 i2c_timing_s1;
+	u32 i2c_timing_s2;
+	u32 i2c_timing_s3;
+	u32 i2c_timing_sla;
+	unsigned int t_start_su, t_start_hd;
+	unsigned int t_stop_su;
+	unsigned int t_data_su, t_data_hd;
+	unsigned int t_scl_l, t_scl_h;
+	unsigned int t_sr_release;
+	unsigned int t_ftl_cycle;
+	unsigned int clkin = clk_get_rate(i2c->clk);
+	unsigned int div, utemp0 = 0, utemp1 = 0, clk_cycle;
+	unsigned int op_clk = (mode == HSI2C_HIGH_SPD) ?
+				i2c->hs_clock : i2c->fs_clock;
+
+	/*
+	 * FPCLK / FI2C =
+	 * (CLK_DIV + 1) * (TSCLK_L + TSCLK_H + 2) + 8 + 2 * FLT_CYCLE
+	 * utemp0 = (CLK_DIV + 1) * (TSCLK_L + TSCLK_H + 2)
+	 * utemp1 = (TSCLK_L + TSCLK_H + 2)
+	 */
+	t_ftl_cycle = (readl(i2c->regs + HSI2C_CONF) >> 16) & 0x7;
+	utemp0 = (clkin / op_clk) - 8 - 2 * t_ftl_cycle;
+
+	/* CLK_DIV max is 256 */
+	for (div = 0; div < 256; div++) {
+		utemp1 = utemp0 / (div + 1);
+
+		/*
+		 * SCL_L and SCL_H each has max value of 255
+		 * Hence, For the clk_cycle to the have right value
+		 * utemp1 has to be less then 512 and more than 4.
+		 */
+		if ((utemp1 < 512) && (utemp1 > 4)) {
+			clk_cycle = utemp1 - 2;
+			break;
+		} else if (div == 255) {
+			dev_warn(i2c->dev, "Failed to calculate divisor");
+			return -EINVAL;
+		}
+	}
+
+	t_scl_l = clk_cycle / 2;
+	t_scl_h = clk_cycle / 2;
+	t_start_su = t_scl_l;
+	t_start_hd = t_scl_l;
+	t_stop_su = t_scl_l;
+	t_data_su = t_scl_l / 2;
+	t_data_hd = t_scl_l / 2;
+	t_sr_release = clk_cycle;
+
+	i2c_timing_s1 = t_start_su << 24 | t_start_hd << 16 | t_stop_su << 8;
+	i2c_timing_s2 = t_data_su << 24 | t_scl_l << 8 | t_scl_h << 0;
+	i2c_timing_s3 = div << 16 | t_sr_release << 0;
+	i2c_timing_sla = t_data_hd << 0;
+
+	dev_dbg(i2c->dev, "tSTART_SU: %X, tSTART_HD: %X, tSTOP_SU: %X\n",
+		t_start_su, t_start_hd, t_stop_su);
+	dev_dbg(i2c->dev, "tDATA_SU: %X, tSCL_L: %X, tSCL_H: %X\n",
+		t_data_su, t_scl_l, t_scl_h);
+	dev_dbg(i2c->dev, "nClkDiv: %X, tSR_RELEASE: %X\n",
+		div, t_sr_release);
+	dev_dbg(i2c->dev, "tDATA_HD: %X\n", t_data_hd);
+
+	if (mode == HSI2C_HIGH_SPD) {
+		writel(i2c_timing_s1, i2c->regs + HSI2C_TIMING_HS1);
+		writel(i2c_timing_s2, i2c->regs + HSI2C_TIMING_HS2);
+		writel(i2c_timing_s3, i2c->regs + HSI2C_TIMING_HS3);
+	} else {
+		writel(i2c_timing_s1, i2c->regs + HSI2C_TIMING_FS1);
+		writel(i2c_timing_s2, i2c->regs + HSI2C_TIMING_FS2);
+		writel(i2c_timing_s3, i2c->regs + HSI2C_TIMING_FS3);
+	}
+	writel(i2c_timing_sla, i2c->regs + HSI2C_TIMING_SLA);
+
+	return 0;
+}
+
+static int exynos5_hsi2c_clock_setup(struct exynos5_i2c *i2c)
+{
+	/*
+	 * Configure the Fast speed timing values
+	 * Even the High Speed mode initially starts with Fast mode
+	 */
+	if (exynos5_i2c_set_timing(i2c, HSI2C_FAST_SPD)) {
+		dev_err(i2c->dev, "HSI2C FS Clock set up failed\n");
+		return -EINVAL;
+	}
+
+	/* configure the High speed timing values */
+	if (i2c->speed_mode == HSI2C_HIGH_SPD) {
+		if (exynos5_i2c_set_timing(i2c, HSI2C_HIGH_SPD)) {
+			dev_err(i2c->dev, "HSI2C HS Clock set up failed\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * exynos5_i2c_init: configures the controller for I2C functionality
+ * Programs I2C controller for Master mode operation
+ */
+static void exynos5_i2c_init(struct exynos5_i2c *i2c)
+{
+	u32 i2c_conf = readl(i2c->regs + HSI2C_CONF);
+
+	writel((HSI2C_FUNC_MODE_I2C | HSI2C_MASTER),
+					i2c->regs + HSI2C_CTL);
+	writel(HSI2C_TRAILING_COUNT, i2c->regs + HSI2C_TRAILIG_CTL);
+
+	if (i2c->speed_mode == HSI2C_HIGH_SPD) {
+		writel(HSI2C_MASTER_ID(MASTER_ID(i2c->bus_id)),
+					i2c->regs + HSI2C_ADDR);
+		i2c_conf |= HSI2C_HS_MODE;
+	}
+
+	writel(i2c_conf | HSI2C_AUTO_MODE, i2c->regs + HSI2C_CONF);
+}
+
+static void exynos5_i2c_reset(struct exynos5_i2c *i2c)
+{
+	u32 i2c_ctl;
+
+	/* Set and clear the bit for reset */
+	i2c_ctl = readl(i2c->regs + HSI2C_CTL);
+	i2c_ctl |= HSI2C_SW_RST;
+	writel(i2c_ctl, i2c->regs + HSI2C_CTL);
+
+	i2c_ctl = readl(i2c->regs + HSI2C_CTL);
+	i2c_ctl &= ~HSI2C_SW_RST;
+	writel(i2c_ctl, i2c->regs + HSI2C_CTL);
+
+	/* We don't expect calculations to fail during the run */
+	exynos5_hsi2c_clock_setup(i2c);
+	/* Initialize the configure registers */
+	exynos5_i2c_init(i2c);
+}
+
+/*
+ * exynos5_i2c_irq: top level IRQ servicing routine
+ *
+ * INT_STATUS registers gives the interrupt details. Further,
+ * FIFO_STATUS or TRANS_STATUS registers are to be check for detailed
+ * state of the bus.
+ */
+static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
+{
+	struct exynos5_i2c *i2c = dev_id;
+	u32 fifo_level, int_status, fifo_status, trans_status;
+	unsigned char byte;
+	int len = 0;
+
+	i2c->state = -EINVAL;
+
+	int_status = readl(i2c->regs + HSI2C_INT_STATUS);
+	fifo_status = readl(i2c->regs + HSI2C_FIFO_STATUS);
+
+	if (int_status & HSI2C_INT_I2C) {
+		trans_status = readl(i2c->regs + HSI2C_TRANS_STATUS);
+		if (trans_status & HSI2C_NO_DEV_ACK) {
+			dev_dbg(i2c->dev, "No ACK from device\n");
+			i2c->state = -ENXIO;
+		} else if (trans_status & HSI2C_NO_DEV) {
+			dev_dbg(i2c->dev, "No device\n");
+			i2c->state = -ENXIO;
+		} else if (trans_status & HSI2C_TRANS_ABORT) {
+			dev_dbg(i2c->dev, "Deal with arbitration lose\n");
+			i2c->state = -EAGAIN;
+		} else if (trans_status & HSI2C_TIMEOUT_AUTO) {
+			dev_dbg(i2c->dev, "Accessing device timed out\n");
+			i2c->state = -EAGAIN;
+		} else if (trans_status & HSI2C_TRANS_DONE) {
+			i2c->trans_done = 1;
+			i2c->state = 0;
+		}
+	}
+	/* TX_ALMOSTEMPTY can happen along with HSI2C_INT_I2C */

The comment says that both can happen, while your code assumes they are 
exlusive.

+	else if (int_status &
+			(HSI2C_INT_TX_UNDERRUN | HSI2C_INT_TX_ALMOSTEMPTY)) {
+		fifo_level = HSI2C_TX_FIFO_LVL(fifo_status);
+
+		/* To support probing the devices for detection */
+		if (i2c->msg->len == 0) {
+			i2c->state = -ENXIO;
+			goto stop;
+		}
+
+		len = HSI2C_FIFO_MAX - fifo_level;
+		if (len > i2c->msg->len)
+			len = i2c->msg->len;
+
+		i2c->msg_len += len;
+		while (len > 0) {
+			byte = i2c->msg->buf[i2c->msg_ptr++];
+			writel(byte, i2c->regs + HSI2C_TX_DATA);
+			len--;
+		}
+		i2c->state = 0;
+		goto stop;
+	}
+	/* If TX FIFO is full (give chance to clear) */
+	else if (int_status & HSI2C_INT_TX_OVERRUN)

Is this even possible? The only reason for TX overrun I can see would be 
the driver trying to put data in FIFO when it doesn't have enough space, 
which shouldn't happen.

+		i2c->state = 0;
+
+	if (int_status & (HSI2C_INT_RX_OVERRUN | HSI2C_INT_TRAILING |
+		HSI2C_INT_RX_UNDERRUN | HSI2C_INT_RX_ALMOSTFULL)) {
+		fifo_level = HSI2C_RX_FIFO_LVL(fifo_status);
+
+		if (fifo_level >= i2c->msg->len)
+			len = i2c->msg->len;
+		else
+			len = fifo_level;
+
+		i2c->msg_len += len;
+		while (len > 0) {
+			byte = (unsigned char)
+				readl(i2c->regs + HSI2C_RX_DATA);
+			i2c->msg->buf[i2c->msg_ptr++] = byte;
+			len--;
+		}
+		i2c->state = 0;
+	}
+
+
+ stop:
+	if ((i2c->msg_len == i2c->msg->len) || (i2c->state < 0)) {
+		writel(0, i2c->regs + HSI2C_INT_ENABLE);
+		complete(&i2c->msg_complete);
+	}
+
+	exynos5_i2c_clr_pend_irq(i2c);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * exynos5_i2c_wait_bus_idle
+ *
+ * Wait for the transaction to complete (indicated by the TRANS_DONE bit
+ * being set), and, if this is the last message in a transfer, wait for
the + * MASTER_BUSY bit to be cleared.
+ *
+ * Returns -EBUSY if the bus cannot be brought to idle
+ */
+static int exynos5_i2c_wait_bus_idle(struct exynos5_i2c *i2c, int stop)
+{
+	unsigned long stop_time;
+	u32 trans_status;
+
+	/* wait for 100 milli seconds for the bus to be idle */
+	stop_time = jiffies + msecs_to_jiffies(100) + 1;
+	do {
+		trans_status = readl(i2c->regs + HSI2C_TRANS_STATUS);
+		if (trans_status & HSI2C_TRANS_DONE)
+			i2c->trans_done = 1;
+		/*
+		 * Only wait for MASTER_BUSY to be cleared if this is the last
+		 * message.
+		 */
+		if ((!stop || !(trans_status & HSI2C_MASTER_BUSY)) &&
+		    i2c->trans_done)
+			return 0;
+
+		usleep_range(50, 200);
+	} while (time_before(jiffies, stop_time));
+
+	return -EBUSY;
+}
+
+/*
+ * exynos5_i2c_message_start: Configures the bus and starts the xfer
+ * i2c: struct exynos5_i2c pointer for the current bus
+ * stop: Enables stop after transfer if set. Set for last transfer of
+ *       in the list of messages.
+ *
+ * Configures the bus for read/write function
+ * Sets chip address to talk to, message length to be sent.
+ * Enables appropriate interrupts and sends start xfer command.
+ */
+static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
+{
+	u32 i2c_ctl;
+	u32 int_en = HSI2C_INT_I2C_EN;
+	u32 i2c_auto_conf = 0;
+	u32 fifo_ctl;
+	u32 i2c_timeout;
+
+	/*
+	 * When the message length is > FIFO depth, set the FIFO trigger
+	 * at FIFO_MAX - 4. Just for ease of handling.
+	 */
+	unsigned short len = (i2c->msg->len > HSI2C_FIFO_MAX) ?
+					(HSI2C_FIFO_MAX - 4) : i2c->msg->len;
+
+	/* Clear to enable Timeout */
+	i2c_timeout = readl(i2c->regs + HSI2C_TIMEOUT);
+	i2c_timeout &= ~HSI2C_TIMEOUT_EN;
+	writel(i2c_timeout, i2c->regs + HSI2C_TIMEOUT);
+
+	fifo_ctl = HSI2C_RXFIFO_EN | HSI2C_TXFIFO_EN;
+	writel(fifo_ctl, i2c->regs + HSI2C_FIFO_CTL);
+
+	i2c_ctl = readl(i2c->regs + HSI2C_CTL);
+	i2c_ctl &= ~(HSI2C_TXCHON | HSI2C_RXCHON);
+	if (i2c->msg->flags & I2C_M_RD) {
+		i2c_ctl |= HSI2C_RXCHON;
+
+		i2c_auto_conf |= HSI2C_READ_WRITE;
+
+		fifo_ctl |= HSI2C_RXFIFO_TRIGGER_LEVEL(len);
+		int_en |= (HSI2C_INT_RX_ALMOSTFULL_EN |
+			HSI2C_INT_TRAILING_EN);
+	} else {
+		i2c_ctl |= HSI2C_TXCHON;
+
+		fifo_ctl |= HSI2C_TXFIFO_TRIGGER_LEVEL(len);
+		int_en |= HSI2C_INT_TX_ALMOSTEMPTY_EN;
+	}
+
+	if (stop == 1)
+		i2c_auto_conf |= HSI2C_STOP_AFTER_TRANS;
+
+	writel(HSI2C_SLV_ADDR_MAS(i2c->msg->addr), i2c->regs + HSI2C_ADDR);
+
+	writel(fifo_ctl, i2c->regs + HSI2C_FIFO_CTL);
+	writel(i2c_ctl, i2c->regs + HSI2C_CTL);
+
+	/* In auto mode the length of xfer cannot be 0 */
+	if (i2c->msg->len == 0)
+		i2c_auto_conf |= 0x1;
+	else
+		i2c_auto_conf |= i2c->msg->len;
+
+	writel(i2c_auto_conf, i2c->regs + HSI2C_AUTO_CONF);
+
+	/* Start data transfer in Master mode */
+	i2c_auto_conf = readl(i2c->regs + HSI2C_AUTO_CONF);
+	i2c_auto_conf |= HSI2C_MASTER_RUN;
+	writel(i2c_auto_conf, i2c->regs + HSI2C_AUTO_CONF);
+
+	writel(int_en, i2c->regs + HSI2C_INT_ENABLE);
+}
+
+static int exynos5_i2c_xfer_msg(struct exynos5_i2c *i2c,
+			      struct i2c_msg *msgs, int stop)
+{
+	unsigned long timeout;
+	int ret;
+
+	i2c->msg = msgs;
+	i2c->msg_ptr = 0;
+	i2c->msg_len = 0;
+	i2c->trans_done = 0;
+
+	INIT_COMPLETION(i2c->msg_complete);
+
+	exynos5_i2c_message_start(i2c, stop);
+
+	timeout = wait_for_completion_timeout
+		(&i2c->msg_complete, EXYNOS5_I2C_TIMEOUT);
+	if (timeout == 0) {
+		exynos5_i2c_reset(i2c);
+		dev_warn(i2c->dev, "%s timeout\n",
+			 (msgs->flags & I2C_M_RD) ? "rx" : "tx");
+		return timeout;
+	}
+
+	ret = i2c->state;
+
+	if (ret == -EAGAIN) {
+		exynos5_i2c_reset(i2c);
+		return ret;
+	}
+
+	/*
+	 * If this is the last message to be transfered (stop == 1)
+	 * Then check if the bus can be brought back to idle.
+	 *
+	 * Return -EBUSY if the bus still busy.
+	 */
+	if (exynos5_i2c_wait_bus_idle(i2c, stop))
+		return -EBUSY;
+
+	/* Return the state as in interrupt routine */
+	return ret;
+}
+
+static int exynos5_i2c_xfer(struct i2c_adapter *adap,
+			struct i2c_msg *msgs, int num)
+{
+	struct exynos5_i2c *i2c = (struct exynos5_i2c *)adap->algo_data;
+	struct i2c_msg *msgs_ptr = msgs;
+	int i = 0;
+	int ret = 0, ret_pm;
+	int stop = 0;
+
+	if (i2c->suspended) {
+		dev_err(i2c->dev, "HS-I2C is not initialzed.\n");
+		return -EIO;
+	}
+
+	ret_pm = pm_runtime_get_sync(i2c->dev);
+	if (IS_ERR_VALUE(ret_pm)) {

This looks wrong to me.

#define MAX_ERRNO       4095
#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)

This makes it:

if (unlikely((ret_pm) >= 0xFFFFF001)

which is obviously impossible for a signed value, such as ret_pm, which can 
be at most 0x7FFFFFFF.

Just check for ret_pm < 0 here and in other occurencies of IS_ERR_VALUE() 
in this driver.

+		ret = -EIO;
+		goto out;
+	}
+
+	clk_prepare_enable(i2c->clk);

Shouldn't this (and any other clock gating/ungating) be inside a runtime PM 
callback? (Also this driver enables runtime PM, but lacks any callbacks. Is 
it really correct?)

+
+	for (i = 0; i < num; i++) {
+		stop = (i == num - 1);
+
+		ret = exynos5_i2c_xfer_msg(i2c, msgs_ptr, stop);
+		msgs_ptr++;
+
+		if (ret < 0)
+			goto out;
+	}
+
+	if (i == num) {
+		ret = num;
+	} else {
+		/* Only one message, cannot access the device */
+		if (i == 1)
+			ret = -EREMOTEIO;
+		else
+			ret = i;
+
+		dev_warn(i2c->dev, "xfer message failed\n");
+	}
+
+ out:
+	clk_disable_unprepare(i2c->clk);
+	pm_runtime_mark_last_busy(i2c->dev);
+	pm_runtime_put_autosuspend(i2c->dev);
+	return ret;
+}
+
+static u32 exynos5_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
+}
+
+static const struct i2c_algorithm exynos5_i2c_algorithm = {
+	.master_xfer		= exynos5_i2c_xfer,
+	.functionality		= exynos5_i2c_func,
+};
+
+static int exynos5_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct exynos5_i2c *i2c;
+	struct resource *mem;
+	unsigned int op_clock;
+	int ret;
+
+	if (!np) {
+		dev_err(&pdev->dev, "no device node\n");
+		return -ENOENT;
+	}
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(struct exynos5_i2c), GFP_KERNEL);
+	if (!i2c) {
+		dev_err(&pdev->dev, "no memory for state\n");
+		return -ENOMEM;
+	}
+
+	if (of_property_read_u32(np, "clock-frequency", &op_clock)) {
+		i2c->speed_mode = HSI2C_FAST_SPD;
+		i2c->fs_clock = HSI2C_FS_TX_CLOCK;
+	}
+
+	if (op_clock >= HSI2C_HS_TX_CLOCK) {
+		i2c->speed_mode = HSI2C_HIGH_SPD;
+		i2c->fs_clock = HSI2C_FS_TX_CLOCK;
+		i2c->hs_clock = op_clock;
+	} else {
+		i2c->speed_mode = HSI2C_FAST_SPD;
+		i2c->fs_clock = op_clock;
+	}
+
+	strlcpy(i2c->adap.name, "exynos5-i2c", sizeof(i2c->adap.name));
+	i2c->adap.owner   = THIS_MODULE;
+	i2c->adap.algo    = &exynos5_i2c_algorithm;
+	i2c->adap.retries = 2;
+
+	i2c->dev = &pdev->dev;
+	i2c->clk = devm_clk_get(&pdev->dev, "hsi2c");
+	if (IS_ERR(i2c->clk)) {
+		dev_err(&pdev->dev, "cannot get clock\n");
+		return -ENOENT;
+	}
+
+	clk_prepare_enable(i2c->clk);
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c->regs = devm_ioremap_resource(&pdev->dev, mem);
+	if (IS_ERR(i2c->regs)) {
+		ret = PTR_ERR(i2c->regs);
+		goto err_clk;
+	}
+
+	i2c->adap.dev.of_node = np;
+	i2c->adap.algo_data = i2c;
+	i2c->adap.dev.parent = &pdev->dev;
+
+	/* Clear pending interrupts from u-boot or misc causes */
+	exynos5_i2c_clr_pend_irq(i2c);
+
+	init_completion(&i2c->msg_complete);
+
+	i2c->irq = ret = irq_of_parse_and_map(np, 0);
+	if (ret <= 0) {
+		dev_err(&pdev->dev, "cannot find HS-I2C IRQ\n");
+		ret = -EINVAL;
+		goto err_clk;
+	}

Please use platform_get_irq(pdev, 0) here. Don't waste the effort that is 
put into creating all those resources by of_platform_populate() early in 
boot process.

+
+	ret = devm_request_irq(&pdev->dev, i2c->irq, exynos5_i2c_irq,
+				0, dev_name(&pdev->dev), i2c);
+
+	if (ret != 0) {
+		dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", i2c->irq);
+		goto err_clk;
+	}
+
+	/*
+	 * TODO: Use private lock to avoid race conditions as
+	 * mentioned in pm_runtime.txt
+	 */
+	pm_runtime_enable(i2c->dev);
+	pm_runtime_set_autosuspend_delay(i2c->dev, EXYNOS5_I2C_PM_TIMEOUT);
+	pm_runtime_use_autosuspend(i2c->dev);
+
+	ret = pm_runtime_get_sync(i2c->dev);
+	if (IS_ERR_VALUE(ret))
+		goto err_clk;
+
+	ret = exynos5_hsi2c_clock_setup(i2c);
+	if (ret)
+		goto err_pm;
+
+	i2c->bus_id = of_alias_get_id(i2c->adap.dev.of_node, "hsi2c");

AFAIK it's responsibility of i2c core to handle this.

+
+	exynos5_i2c_init(i2c);
+
+	ret = i2c_add_adapter(&i2c->adap);

You can call i2c_add_numbered_adapter() here to make i2c core assign a 
number to your adapter, either automatically or using device tree alias.

Best regards,
Tomasz

+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to add bus to i2c core\n");
+		goto err_pm;
+	}
+
+	of_i2c_register_devices(&i2c->adap);
+	platform_set_drvdata(pdev, i2c);
+
+	clk_disable_unprepare(i2c->clk);
+	pm_runtime_mark_last_busy(i2c->dev);
+	pm_runtime_put_autosuspend(i2c->dev);
+
+	return 0;
+
+ err_pm:
+	pm_runtime_put(i2c->dev);
+	pm_runtime_disable(&pdev->dev);
+ err_clk:
+	clk_disable_unprepare(i2c->clk);
+	return ret;
+}
+
+static int exynos5_i2c_remove(struct platform_device *pdev)
+{
+	struct exynos5_i2c *i2c = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pm_runtime_get_sync(&pdev->dev);
+	if (IS_ERR_VALUE(ret))
+		return ret;
+
+	i2c_del_adapter(&i2c->adap);
+
+	pm_runtime_put(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
+	clk_disable_unprepare(i2c->clk);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int exynos5_i2c_suspend_noirq(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct exynos5_i2c *i2c = platform_get_drvdata(pdev);
+
+	i2c->suspended = 1;
+
+	return 0;
+}
+
+static int exynos5_i2c_resume_noirq(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct exynos5_i2c *i2c = platform_get_drvdata(pdev);
+	int ret = 0;
+
+	clk_prepare_enable(i2c->clk);
+
+	ret = exynos5_hsi2c_clock_setup(i2c);
+	if (ret) {
+		clk_disable_unprepare(i2c->clk);
+		return ret;
+	}
+
+	exynos5_i2c_init(i2c);
+	clk_disable_unprepare(i2c->clk);
+	i2c->suspended = 0;
+
+	return 0;
+}
+
+static const struct dev_pm_ops exynos5_i2c_dev_pm_ops = {
+	.suspend_noirq = exynos5_i2c_suspend_noirq,
+	.resume_noirq	= exynos5_i2c_resume_noirq,
+};
+
+#define EXYNOS5_DEV_PM_OPS (&exynos5_i2c_dev_pm_ops)
+#else
+#define EXYNOS5_DEV_PM_OPS NULL
+#endif
+
+static struct platform_driver exynos5_i2c_driver = {
+	.probe		= exynos5_i2c_probe,
+	.remove		= exynos5_i2c_remove,
+	.driver		= {
+		.owner	= THIS_MODULE,
+		.name	= "exynos5-hsi2c",
+		.pm	= EXYNOS5_DEV_PM_OPS,
+		.of_match_table = exynos5_i2c_match,
+	},
+};
+
+module_platform_driver(exynos5_i2c_driver);
+
+MODULE_DESCRIPTION("Exynos5 HS-I2C Bus driver");
+MODULE_AUTHOR("Naveen Krishna Chatradhi, [off-list ref]");
+MODULE_AUTHOR("Taekgyun Ko, [off-list ref]");
+MODULE_LICENSE("GPL v2");