Message-ID: <20180630081359.GA5389@Mani-XPS-13-9360>
Date:   Sat, 30 Jun 2018 13:43:59 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Peter Rosin <peda@...ntia.se>
Cc:     wsa@...-dreams.de, robh+dt@...nel.org, afaerber@...e.de,
        linus.walleij@...aro.org, linux-i2c@...r.kernel.org,
        liuwei@...ions-semi.com, mp-cs@...ions-semi.com,
        96boards@...obotics.com, devicetree@...r.kernel.org,
        andy.shevchenko@...il.com, daniel.thompson@...aro.org,
        amit.kucheria@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        hzhang@...obotics.com, bdong@...obotics.com,
        manivannanece23@...il.com, thomas.liau@...ions-semi.com,
        jeff.chen@...ions-semi.com
Subject: Re: [PATCH v2 5/6] i2c: Add Actions Semi OWL family S900 I2C driver

Hi Peter,

Thanks for the review!

On Fri, Jun 29, 2018 at 06:45:19AM +0200, Peter Rosin wrote:
> On June 28, 2018 8:10:41 PM GMT+02:00, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> >Add Actions Semi OWL family S900 I2C driver.
> >
> >Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> >---
> > drivers/i2c/busses/Kconfig   |   7 +
> > drivers/i2c/busses/Makefile  |   1 +
> > drivers/i2c/busses/i2c-owl.c | 471 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 479 insertions(+)
> > create mode 100644 drivers/i2c/busses/i2c-owl.c
> >
> >diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> >index 4f8df2ec87b1..2062da17e33b 100644
> >--- a/drivers/i2c/busses/Kconfig
> >+++ b/drivers/i2c/busses/Kconfig
> >@@ -762,6 +762,13 @@ config I2C_OMAP
> > 	  Like OMAP1510/1610/1710/5912 and OMAP242x.
> > 	  For details see http://www.ti.com/omap.
> > 
> >+config I2C_OWL
> >+	tristate "OWL I2C Controller"
> >+	depends on ARCH_ACTIONS || COMPILE_TEST
> >+	help
> >+	  Say Y here if you want to use the I2C bus controller on
> >+	  the Actions Semi OWL SoCs.
> >+
> > config I2C_PASEMI
> > 	tristate "PA Semi SMBus interface"
> > 	depends on PPC_PASEMI && PCI
> >diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> >index 5a869144a0c5..b71618f77880 100644
> >--- a/drivers/i2c/busses/Makefile
> >+++ b/drivers/i2c/busses/Makefile
> >@@ -76,6 +76,7 @@ obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
> > obj-$(CONFIG_I2C_NOMADIK)	+= i2c-nomadik.o
> > obj-$(CONFIG_I2C_OCORES)	+= i2c-ocores.o
> > obj-$(CONFIG_I2C_OMAP)		+= i2c-omap.o
> >+obj-$(CONFIG_I2C_OWL)		+= i2c-owl.o
> > obj-$(CONFIG_I2C_PASEMI)	+= i2c-pasemi.o
> > obj-$(CONFIG_I2C_PCA_PLATFORM)	+= i2c-pca-platform.o
> > obj-$(CONFIG_I2C_PMCMSP)	+= i2c-pmcmsp.o
> >diff --git a/drivers/i2c/busses/i2c-owl.c
> >b/drivers/i2c/busses/i2c-owl.c
> >new file mode 100644
> >index 000000000000..12320fca6755
> >--- /dev/null
> >+++ b/drivers/i2c/busses/i2c-owl.c
> >@@ -0,0 +1,471 @@
> >+// SPDX-License-Identifier: GPL-2.0+
> >+/*
> >+ * OWL SoC's I2C driver
> >+ *
> >+ * Copyright (c) 2014 Actions Semi Inc.
> >+ * Author: David Liu <liuwei@...ions-semi.com>
> >+ *
> >+ * Copyright (c) 2018 Linaro Ltd.
> >+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> >+ */
> >+
> >+#include <linux/clk.h>
> >+#include <linux/delay.h>
> >+#include <linux/i2c.h>
> >+#include <linux/interrupt.h>
> >+#include <linux/module.h>
> >+#include <linux/of_device.h>
> >+#include <linux/io.h>
> 
> I would have kept this list fully sorted.
> 

Ack.

> >+
> >+/* I2C registers */
> >+#define OWL_I2C_REG_CTL		0x0000
> >+#define OWL_I2C_REG_CLKDIV	0x0004
> >+#define OWL_I2C_REG_STAT	0x0008
> >+#define OWL_I2C_REG_ADDR	0x000C
> >+#define OWL_I2C_REG_TXDAT	0x0010
> >+#define OWL_I2C_REG_RXDAT	0x0014
> >+#define OWL_I2C_REG_CMD		0x0018
> >+#define OWL_I2C_REG_FIFOCTL	0x001C
> >+#define OWL_I2C_REG_FIFOSTAT	0x0020
> >+#define OWL_I2C_REG_DATCNT	0x0024
> >+#define OWL_I2C_REG_RCNT	0x0028
> >+
> >+/* I2Cx_CTL Bit Mask */
> >+#define OWL_I2C_CTL_RB		BIT(1)
> >+#define OWL_I2C_CTL_GBCC(x)	(((x) & 0x3) << 2)
> >+#define	OWL_I2C_CTL_GBCC_NONE	OWL_I2C_CTL_GBCC(0)
> >+#define	OWL_I2C_CTL_GBCC_START	OWL_I2C_CTL_GBCC(1)
> >+#define	OWL_I2C_CTL_GBCC_STOP	OWL_I2C_CTL_GBCC(2)
> >+#define	OWL_I2C_CTL_GBCC_RSTART	OWL_I2C_CTL_GBCC(3)
> >+#define OWL_I2C_CTL_IRQE	BIT(5)
> >+#define OWL_I2C_CTL_EN		BIT(7)
> >+#define OWL_I2C_CTL_AE		BIT(8)
> >+#define OWL_I2C_CTL_SHSM	BIT(10)
> >+
> >+#define OWL_I2C_DIV_FACTOR(x)	((x) & 0xff)
> >+
> >+/* I2Cx_STAT Bit Mask */
> >+#define OWL_I2C_STAT_RACK	BIT(0)
> >+#define OWL_I2C_STAT_BEB	BIT(1)
> >+#define OWL_I2C_STAT_IRQP	BIT(2)
> >+#define OWL_I2C_STAT_LAB	BIT(3)
> >+#define OWL_I2C_STAT_STPD	BIT(4)
> >+#define OWL_I2C_STAT_STAD	BIT(5)
> >+#define OWL_I2C_STAT_BBB	BIT(6)
> >+#define OWL_I2C_STAT_TCB	BIT(7)
> >+#define OWL_I2C_STAT_LBST	BIT(8)
> >+#define OWL_I2C_STAT_SAMB	BIT(9)
> >+#define OWL_I2C_STAT_SRGC	BIT(10)
> >+
> >+/* I2Cx_CMD Bit Mask */
> >+#define OWL_I2C_CMD_SBE		BIT(0)
> >+#define OWL_I2C_CMD_RBE		BIT(4)
> >+#define OWL_I2C_CMD_DE		BIT(8)
> >+#define OWL_I2C_CMD_NS		BIT(9)
> >+#define OWL_I2C_CMD_SE		BIT(10)
> >+#define OWL_I2C_CMD_MSS		BIT(11)
> >+#define OWL_I2C_CMD_WRS		BIT(12)
> >+#define OWL_I2C_CMD_SECL	BIT(15)
> >+
> >+#define OWL_I2C_CMD_AS(x)	(((x) & 0x7) << 1)
> >+#define OWL_I2C_CMD_SAS(x)	(((x) & 0x7) << 5)
> >+
> >+/* I2Cx_FIFOCTL Bit Mask */
> >+#define OWL_I2C_FIFOCTL_NIB	BIT(0)
> >+#define OWL_I2C_FIFOCTL_RFR	BIT(1)
> >+#define OWL_I2C_FIFOCTL_TFR	BIT(2)
> >+
> >+/* I2Cc_FIFOSTAT Bit Mask */
> >+#define OWL_I2C_FIFOSTAT_RNB	BIT(1)
> >+#define OWL_I2C_FIFOSTAT_RFE	BIT(2)
> >+#define OWL_I2C_FIFOSTAT_TFF	BIT(5)
> >+#define OWL_I2C_FIFOSTAT_TFD	GENMASK(23, 16)
> >+#define OWL_I2C_FIFOSTAT_RFD	GENMASK(15, 8)
> >+
> >+/* I2C bus timeout */
> >+#define OWL_I2C_TIMEOUT		msecs_to_jiffies(4 * 1000)
> >+
> >+#define OWL_I2C_MAX_RETRIES	50
> >+
> >+#define OWL_I2C_DEFAULT_SPEED	100000
> >+#define OWL_I2C_MAX_SPEED	400000
> >+
> >+struct owl_i2c_dev {
> >+	struct i2c_adapter	adap;
> >+	struct i2c_msg		*msg;
> >+	struct completion	msg_complete;
> >+	struct clk		*clk;
> >+	void __iomem		*base;
> >+	unsigned long		clk_rate;
> >+	u32			bus_freq;
> >+	u32			msg_ptr;
> >+};
> >+
> >+static void owl_i2c_update_reg(void __iomem *base, unsigned int val,
> >bool state)
> 
> Is base really a good name here? I would go with reg.
>

Okay, will change it to reg.

> >+{
> >+	unsigned int regval;
> >+
> >+	regval = readl(base);
> >+
> >+	if (state)
> >+		regval |= val;
> >+	else
> >+		regval &= ~val;
> >+
> >+	writel(regval, base);
> >+}
> >+
> >+static int owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
> >+{
> >+	unsigned int val, timeout = 0;
> >+
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+				OWL_I2C_CTL_EN, false);
> >+	mdelay(1);
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+				OWL_I2C_CTL_EN, true);
> >+
> >+	/* Reset FIFO */
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
> >+				OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR,
> >+				true);
> >+
> >+	/* Wait 50ms for FIFO reset complete */
> >+	do {
> >+		val = readl(i2c_dev->base + OWL_I2C_REG_FIFOCTL);
> >+		if (!(val & (OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR)))
> >+			break;
> >+		mdelay(1);
> >+	} while (timeout++ < OWL_I2C_MAX_RETRIES);
> >+
> >+	if (timeout > OWL_I2C_MAX_RETRIES) {
> >+		dev_err(&i2c_dev->adap.dev, "FIFO reset timeout");
> >+		return -ETIMEDOUT;
> >+	}
> >+
> >+	/* Clear status registers */
> >+	writel(0, i2c_dev->base + OWL_I2C_REG_STAT);
> >+
> >+	return 0;
> >+}
> 
> This ..._reset function does a number of unlocked read-modify-write cycles, and it is called from an interrupt. Is that safe? What if a spurious interrupt happen?
>

hmmm, nice catch. I think it is safe to remove the rest function from
the handler. Anyhow we call reset during the start of the transfer so
it doesn't makes any difference IMO.

> >+
> >+static int owl_i2c_set_freq(struct owl_i2c_dev *i2c_dev)
> >+{
> >+	unsigned int val;
> >+
> >+	val = (i2c_dev->clk_rate + i2c_dev->bus_freq * 16 - 1) /
> >+				(i2c_dev->bus_freq * 16);
> >+
> >+	/* Set clock divider factor */
> >+	writel(OWL_I2C_DIV_FACTOR(val), i2c_dev->base + OWL_I2C_REG_CLKDIV);
> >+
> >+	return 0;
> >+}
> >+
> >+static int owl_i2c_hw_init(struct owl_i2c_dev *i2c_dev)
> >+{
> >+	int ret;
> >+
> >+	/* Reset I2C controller */
> >+	ret = owl_i2c_reset(i2c_dev);
> >+	if (ret)
> >+		return ret;
> >+
> >+	/* Set bus frequency */
> >+	return owl_i2c_set_freq(i2c_dev);
> >+}
> >+
> >+static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
> >+{
> >+	struct owl_i2c_dev *i2c_dev = _dev;
> >+	struct i2c_msg *msg = i2c_dev->msg;
> >+	unsigned int stat, fifostat;
> >+
> >+	fifostat = readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT);
> >+	if (fifostat & OWL_I2C_FIFOSTAT_RNB) {
> >+		dev_dbg(&i2c_dev->adap.dev, "received NACK from device");
> >+		owl_i2c_reset(i2c_dev);
> >+		goto stop;
> >+	}
> >+
> >+	stat = readl(i2c_dev->base + OWL_I2C_REG_STAT);
> >+	if (stat & OWL_I2C_STAT_BEB) {
> >+		dev_dbg(&i2c_dev->adap.dev, "bus error");
> >+		owl_i2c_reset(i2c_dev);
> >+		goto stop;
> >+	}
> >+
> >+	/* Handle FIFO read */
> >+	if (msg->flags & I2C_M_RD) {
> >+		while ((readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
> >+				OWL_I2C_FIFOSTAT_RFE) &&
> >+				(i2c_dev->msg_ptr < msg->len)) {
> >+			msg->buf[i2c_dev->msg_ptr++] = readl(i2c_dev->base +
> >+							OWL_I2C_REG_RXDAT);
> >+		}
> >+	} else {
> >+		/* Handle the remaining bytes which were not sent */
> >+		while (!(readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
> >+				OWL_I2C_FIFOSTAT_TFF) &&
> >+				i2c_dev->msg_ptr < msg->len) {
> >+			writel(msg->buf[i2c_dev->msg_ptr++], i2c_dev->base +
> >+							OWL_I2C_REG_TXDAT);
> >+		}
> >+	}
> >+
> >+stop:
> >+	/* Clear pending interrupts */
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_STAT,
> >+				OWL_I2C_STAT_IRQP, true);
> >+
> >+	complete_all(&i2c_dev->msg_complete);
> >+
> >+	return IRQ_HANDLED;
> >+}
> >+
> >+static u32 owl_i2c_func(struct i2c_adapter *adap)
> >+{
> >+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> >+}
> >+
> >+static int owl_i2c_check_bus_busy(struct i2c_adapter *adap)
> >+{
> >+	struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> >+	unsigned long timeout;
> >+	unsigned int val;
> >+
> >+	/* Check for Arbitration lost */
> >+	val = readl(i2c_dev->base + OWL_I2C_REG_STAT);
> >+	if (val & OWL_I2C_STAT_LAB) {
> >+		val &= ~OWL_I2C_STAT_LAB;
> >+		writel(val, i2c_dev->base + OWL_I2C_REG_STAT);
> >+		return -EAGAIN;
> >+	}
> >+
> >+	/* Check for Bus busy */
> >+	timeout = jiffies + OWL_I2C_TIMEOUT;
> >+	while (readl(i2c_dev->base + OWL_I2C_REG_STAT) & OWL_I2C_STAT_BBB) {
> >+		if (time_after(jiffies, timeout)) {
> >+			dev_err(&adap->dev, "Bus busy timeout");
> >+			return -ETIMEDOUT;
> >+		}
> >+	}
> >+
> >+	return 0;
> >+}
> >+
> >+static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct
> >i2c_msg *msgs,
> >+				int num)
> >+{
> >+	struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> >+	struct i2c_msg *msg;
> >+	unsigned long time_left;
> >+	unsigned int i2c_cmd;
> >+	unsigned int addr;
> >+	int ret = 0, idx;
> >+
> >+	ret = owl_i2c_hw_init(i2c_dev);
> >+	if (ret)
> >+		return ret;
> >+
> >+	ret = owl_i2c_check_bus_busy(adap);
> >+	if (ret)
> >+		return ret;
> >+
> >+	reinit_completion(&i2c_dev->msg_complete);
> >+
> >+	/* Enable I2C controller interrupt */
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+				OWL_I2C_CTL_IRQE, true);
> >+
> >+	/*
> >+	 * Select: FIFO enable, Master mode, Stop enable, Data count enable,
> >+	 * Send start bit
> >+	 */
> >+	i2c_cmd = (OWL_I2C_CMD_SECL | OWL_I2C_CMD_MSS | OWL_I2C_CMD_SE
> >+			| OWL_I2C_CMD_NS | OWL_I2C_CMD_DE | OWL_I2C_CMD_SBE);
> >+
> >+	/* Handle repeated start condition */
> >+	if (num > 1) {
> >+		/* Set internal address length and enable repeated start */
> >+		i2c_cmd |= (OWL_I2C_CMD_AS(msgs[0].len + 1)
> >+				| OWL_I2C_CMD_SAS(1) | OWL_I2C_CMD_RBE);
> >+
> >+		/* Write slave address */
> >+		addr = i2c_8bit_addr_from_msg(&msgs[0]);
> >+		writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);
> >+
> >+		/* Write internal register address */
> >+		for (idx = 0; idx < msgs[0].len; idx++)
> >+			writel(msgs[0].buf[idx], i2c_dev->base +
> >+						OWL_I2C_REG_TXDAT);
> >+
> >+		msg = &msgs[1];
> >+	} else {
> >+		/* Set address length */
> >+		i2c_cmd |= OWL_I2C_CMD_AS(1);
> >+		msg = &msgs[0];
> >+	}
> >+
> >+	i2c_dev->msg = msg;
> >+	i2c_dev->msg_ptr = 0;
> >+
> >+	/* Set data count for the message */
> >+	writel(msg->len, i2c_dev->base + OWL_I2C_REG_DATCNT);
> >+
> >+	addr = i2c_8bit_addr_from_msg(msg);
> >+	writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);
> >+
> >+	if (!(msg->flags & I2C_M_RD)) {
> >+		/* Write data to FIFO */
> >+		for (idx = 0; idx < msg->len; idx++) {
> >+			/* Check for FIFO full */
> >+			if (readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT)
> >+					& OWL_I2C_FIFOSTAT_TFF)
> 
> You should cleanup here, and return some error. I think? Or, why do you break out of the loop early?
> 

Actually we break the loop once the FIFO is full. Since the total
number of messages handled (240 bytes) is greater than the FIFO depth
(128 bytes) we handle the remaining bytes in the handler.

> >+				break;
> >+
> >+			writel(msg->buf[idx],
> >+					i2c_dev->base + OWL_I2C_REG_TXDAT);
> >+		}
> >+
> >+		i2c_dev->msg_ptr = idx;
> >+	}
> >+
> >+	/* Ignore the NACK if needed */
> >+	if (msg->flags & I2C_M_IGNORE_NAK)
> >+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
> >+				OWL_I2C_FIFOCTL_NIB, true);
> >+	else
> >+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
> >+				OWL_I2C_FIFOCTL_NIB, false);
> >+
> >+	/* Start the transfer */
> >+	writel(i2c_cmd, i2c_dev->base + OWL_I2C_REG_CMD);
> >+
> >+	time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> >+						adap->timeout);
> >+	if (time_left == 0) {
> >+		dev_err(&adap->dev, "Transaction timed out");
> >+		/* Send stop condition and release the bus */
> >+		owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+			OWL_I2C_CTL_GBCC_STOP | OWL_I2C_CTL_RB, true);
> >+		ret = -ETIMEDOUT;
> >+	}
> >+
> >+	/* Disable I2C controller */
> >+	owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+				OWL_I2C_CTL_EN, false);
> >+
> >+	return i2c_dev->msg_ptr ? num : i2c_dev->msg_ptr;
> 
> This is wrong. Should probably be
> 
>    return ret ?: num;
> 

Agree. But there is one more issue here. We may enter the handler and
do neither read nor write for cases like i2c-detect and returning num
for those cases will make no sense. I guess this can be handled as
below:

Let's assume ret = 0, then

        if (i2c_dev->msg_ptr == msg->len)
                ret = num;

	return ret;

What do you think?

Thanks,
Mani

> Cheers,
> Peter
> 
> >+}
> >+
> >+static const struct i2c_algorithm owl_i2c_algorithm = {
> >+	.master_xfer    = owl_i2c_master_xfer,
> >+	.functionality  = owl_i2c_func
> >+};
> >+
> >+static const struct i2c_adapter_quirks owl_i2c_quirks = {
> >+	.flags		= I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST,
> >+	.max_read_len   = 240,
> >+	.max_write_len  = 240,
> >+	.max_comb_1st_msg_len = 6,
> >+	.max_comb_2nd_msg_len = 240
> >+};
> >+
> >+static int owl_i2c_probe(struct platform_device *pdev)
> >+{
> >+	struct device *dev = &pdev->dev;
> >+	struct owl_i2c_dev *i2c_dev;
> >+	struct resource *res;
> >+	int ret, irq;
> >+
> >+	i2c_dev = devm_kzalloc(dev, sizeof(*i2c_dev), GFP_KERNEL);
> >+	if (!i2c_dev)
> >+		return -ENOMEM;
> >+
> >+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >+	i2c_dev->base = devm_ioremap_resource(dev, res);
> >+	if (IS_ERR(i2c_dev->base))
> >+		return PTR_ERR(i2c_dev->base);
> >+
> >+	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",
> >+					&i2c_dev->bus_freq))
> >+		i2c_dev->bus_freq = OWL_I2C_DEFAULT_SPEED;
> >+
> >+	/* We support only frequencies of 100k and 400k for now */
> >+	if (i2c_dev->bus_freq != OWL_I2C_DEFAULT_SPEED &&
> >+			i2c_dev->bus_freq > OWL_I2C_MAX_SPEED) {
> >+		dev_err(dev, "invalid clock-frequency %d\n", i2c_dev->bus_freq);
> >+		return -EINVAL;
> >+	}
> >+
> >+	i2c_dev->clk = devm_clk_get(dev, NULL);
> >+	if (IS_ERR(i2c_dev->clk)) {
> >+		dev_err(dev, "failed to get clock\n");
> >+		return PTR_ERR(i2c_dev->clk);
> >+	}
> >+
> >+	ret = clk_prepare_enable(i2c_dev->clk);
> >+	if (ret)
> >+		return ret;
> >+
> >+	i2c_dev->clk_rate = clk_get_rate(i2c_dev->clk);
> >+	if (!i2c_dev->clk_rate) {
> >+		dev_err(dev, "input clock rate should not be zero\n");
> >+		ret = -EINVAL;
> >+		goto disable_clk;
> >+	}
> >+
> >+	init_completion(&i2c_dev->msg_complete);
> >+	i2c_dev->adap.owner = THIS_MODULE;
> >+	i2c_dev->adap.algo = &owl_i2c_algorithm;
> >+	i2c_dev->adap.timeout = OWL_I2C_TIMEOUT;
> >+	i2c_dev->adap.quirks = &owl_i2c_quirks;
> >+	i2c_dev->adap.dev.parent = dev;
> >+	i2c_dev->adap.dev.of_node = dev->of_node;
> >+	snprintf(i2c_dev->adap.name, sizeof(i2c_dev->adap.name),
> >+			"%s", "OWL I2C adapter");
> >+	i2c_set_adapdata(&i2c_dev->adap, i2c_dev);
> >+
> >+	platform_set_drvdata(pdev, i2c_dev);
> >+
> >+	ret = devm_request_irq(dev, irq, owl_i2c_interrupt, 0, pdev->name,
> >+				i2c_dev);
> >+	if (ret) {
> >+		dev_err(dev, "failed to request irq %d\n", irq);
> >+		goto disable_clk;
> >+	}
> >+
> >+	return i2c_add_adapter(&i2c_dev->adap);
> >+
> >+disable_clk:
> >+	clk_disable_unprepare(i2c_dev->clk);
> >+
> >+	return ret;
> >+}
> >+
> >+static const struct of_device_id owl_i2c_of_match[] = {
> >+	{.compatible = "actions,s900-i2c"},
> >+	{ /* sentinel */ }
> >+};
> >+MODULE_DEVICE_TABLE(of, owl_i2c_of_match);
> >+
> >+static struct platform_driver owl_i2c_driver = {
> >+	.probe		= owl_i2c_probe,
> >+	.driver		= {
> >+		.name	= "owl-i2c",
> >+		.of_match_table = of_match_ptr(owl_i2c_of_match),
> >+	},
> >+};
> >+module_platform_driver(owl_i2c_driver);
> >+
> >+MODULE_AUTHOR("David Liu <liuwei@...ions-semi.com>");
> >+MODULE_AUTHOR("Manivannan Sadhasivam
> ><manivannan.sadhasivam@...aro.org>");
> >+MODULE_DESCRIPTION("Actions Semi OWL SoCs I2C driver");
> >+MODULE_LICENSE("GPL");
> 

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