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SubjectRe: [PATCH v3 5/6] i2c: Add Actions Semiconductor Owl family S900 I2C driver
Hi Peter,

On Sun, Jul 01, 2018 at 06:57:54AM +0200, Peter Rosin wrote:
> On June 30, 2018 3:33:29 PM GMT+02:00, Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> wrote:
> >Add Actions Semiconductor Owl family S900 I2C driver.
> >
> >Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> >---
> > drivers/i2c/busses/Kconfig | 7 +
> > drivers/i2c/busses/Makefile | 1 +
> > drivers/i2c/busses/i2c-owl.c | 477 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 485 insertions(+)
> > create mode 100644 drivers/i2c/busses/i2c-owl.c
> >
> >diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> >index 4f8df2ec87b1..8c8025f87ce4 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 "Actions Semiconductor 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 Semiconductor Owl SoC's.
> >+
> > 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..144a249bf994
> >--- /dev/null
> >+++ b/drivers/i2c/busses/i2c-owl.c
> >@@ -0,0 +1,477 @@
> >+// SPDX-License-Identifier: GPL-2.0+
> >+/*
> >+ * Actions Semiconductor Owl SoC's I2C driver
> >+ *
> >+ * Copyright (c) 2014 Actions Semi Inc.
> >+ * Author: David Liu <liuwei@actions-semi.com>
> >+ *
> >+ * Copyright (c) 2018 Linaro Ltd.
> >+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> >+ */
> >+
> >+#include <linux/clk.h>
> >+#include <linux/delay.h>
> >+#include <linux/i2c.h>
> >+#include <linux/interrupt.h>
> >+#include <linux/io.h>
> >+#include <linux/module.h>
> >+#include <linux/of_device.h>
> >+
> >+/* 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_DEF_SPEED_HZ 100000
> >+#define OWL_I2C_MAX_SPEED_HZ 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 *reg, unsigned int val,
> >bool state)
> >+{
> >+ unsigned int regval;
> >+
> >+ regval = readl(reg);
> >+
> >+ if (state)
> >+ regval |= val;
> >+ else
> >+ regval &= ~val;
> >+
> >+ writel(regval, reg);
> >+}
> >+
> >+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;
> >+}
> >+
> >+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");
> >+ 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");
> >+ 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);
> >+
>
> Here is a read-modify-write on ..._REG_STAT from interrupt context...
>

Will use spinlock for the entire handler.

> >+ 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);
>
> ...and here is one from process context.
>
> Can they cross? If not, why? Either use some locking, or add a comment explaining why this is safe.
>

As said above, this function will be protected by spinlock.

> >+ 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, 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)
> >+ 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;
> >+ }
> >+
> >+ /*
> >+ * By default, 0 will be returned if interrupt occurred but no
> >+ * read or write happened. Else if msg_ptr equals to message length,
> >+ * message count will be returned.
> >+ */
>
> Zero is never a valid return value for this function. It has to be either num or a negative error. So, this comment is bad, which makes me assume the code is too. I didn't bother to check any further...
>

hmm, okay. Can you please suggest an error value for this case? I mean
when the handler got triggered but no read/write happened.

Thanks,
Mani

> Cheers,
> Peter
>
> >+ if (i2c_dev->msg_ptr == msg->len)
> >+ ret = num;
> >+
> >+ /* Disable I2C controller */
> >+ owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> >+ OWL_I2C_CTL_EN, false);
> >+
> >+ return ret;
> >+}
> >+
> >+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_DEF_SPEED_HZ;
> >+
> >+ /* We support only frequencies of 100k and 400k for now */
> >+ if (i2c_dev->bus_freq != OWL_I2C_DEF_SPEED_HZ &&
> >+ i2c_dev->bus_freq > OWL_I2C_MAX_SPEED_HZ) {
> >+ 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@actions-semi.com>");
> >+MODULE_AUTHOR("Manivannan Sadhasivam
> ><manivannan.sadhasivam@linaro.org>");
> >+MODULE_DESCRIPTION("Actions Semiconductor Owl SoC's I2C driver");
> >+MODULE_LICENSE("GPL");
>

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