Message-ID: <20170125093853.GB5662@dragon>
Date:   Wed, 25 Jan 2017 17:38:55 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Baoyou Xie <baoyou.xie@...aro.org>
Cc:     andy.shevchenko@...il.com, jun.nie@...aro.org, wsa@...-dreams.de,
        robh+dt@...nel.org, mark.rutland@....com,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        xie.baoyou@....com.cn, chen.chaokai@....com.cn,
        wang.qiang01@....com.cn
Subject: Re: [PATCH v2 3/3] i2c: zx2967: add i2c controller driver for ZTE's
 zx2967 family

On Mon, Jan 23, 2017 at 01:03:26PM +0800, Baoyou Xie wrote:
> This patch adds i2c controller driver for ZTE's zx2967 family.
> 
> Signed-off-by: Baoyou Xie <baoyou.xie@...aro.org>
> ---
>  drivers/i2c/busses/Kconfig      |   9 +
>  drivers/i2c/busses/Makefile     |   1 +
>  drivers/i2c/busses/i2c-zx2967.c | 690 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 700 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-zx2967.c
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index e4a603e..9609f45 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -1246,4 +1246,13 @@ config I2C_OPAL
>  	  This driver can also be built as a module. If so, the module will be
>  	  called as i2c-opal.
>  
> +config I2C_ZX2967
> +	tristate "ZTE zx2967 I2C support"
> +	depends on ARCH_ZX
> +	default y
> +	help
> +	  Selecting this option will add ZX2967 I2C driver.
> +	  This driver can also be built as a module. If so, the module will be
> +	  called zx2967_i2c.

Called zx2967_i2c?  Is it the .ko filename or the name we see in lsmod
command output?  From what I have seen, neither of the names is
zx2967_i2c.

Also, I see the following failure in module installation.

$ insmod i2c-zx2967.ko 
i2c_zx2967: Unknown symbol __clk_get_enable_count (err 0)
Error: could not insert module i2c-zx2967.ko: Unknown symbol in module

> +
>  endmenu
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index beb4809..16b2901 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -101,6 +101,7 @@ obj-$(CONFIG_I2C_XILINX)	+= i2c-xiic.o
>  obj-$(CONFIG_I2C_XLR)		+= i2c-xlr.o
>  obj-$(CONFIG_I2C_XLP9XX)	+= i2c-xlp9xx.o
>  obj-$(CONFIG_I2C_RCAR)		+= i2c-rcar.o
> +obj-$(CONFIG_I2C_ZX2967)	+= i2c-zx2967.o
>  
>  # External I2C/SMBus adapter drivers
>  obj-$(CONFIG_I2C_DIOLAN_U2C)	+= i2c-diolan-u2c.o
> diff --git a/drivers/i2c/busses/i2c-zx2967.c b/drivers/i2c/busses/i2c-zx2967.c
> new file mode 100644
> index 0000000..d38b7b7
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-zx2967.c
> @@ -0,0 +1,690 @@
> +/*
> + * ZTE's zx2967 family i2c bus controller driver
> + *
> + * Copyright (C) 2017 ZTE Ltd.
> + *
> + * Author: Baoyou Xie <baoyou.xie@...aro.org>
> + *
> + * License terms: GNU General Public License (GPL) version 2
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>

clk-provider.h is only meant to be included by clock driver, not client
device drivers.

> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/pinctrl/consumer.h>
> +#include <linux/platform_device.h>
> +
> +#define REG_CMD				0x04
> +#define REG_DEVADDR_H			0x0C
> +#define REG_DEVADDR_L			0x10
> +#define REG_CLK_DIV_FS			0x14
> +#define REG_CLK_DIV_HS			0x18
> +#define REG_WRCONF			0x1C
> +#define REG_RDCONF			0x20
> +#define REG_DATA			0x24
> +#define REG_STAT			0x28
> +
> +#define I2C_STOP			0
> +#define I2C_MASTER			BIT(0)
> +#define I2C_ADDR_MODE_TEN		BIT(1)
> +#define I2C_IRQ_MSK_ENABLE		BIT(3)
> +#define I2C_RW_READ			BIT(4)
> +#define I2C_CMB_RW_EN			BIT(5)
> +#define I2C_START			BIT(6)
> +#define I2C_ADDR_MODE_TEN		BIT(1)
> +
> +#define I2C_WFIFO_RESET			BIT(7)
> +#define I2C_RFIFO_RESET			BIT(7)
> +
> +#define I2C_IRQ_ACK_CLEAR		BIT(7)
> +#define I2C_INT_MASK			GENMASK(6, 0)
> +
> +#define I2C_TRANS_DONE			BIT(0)
> +#define I2C_ERROR_DEVICE		BIT(1)
> +#define I2C_ERROR_DATA			BIT(2)
> +#define I2C_ERROR_MASK			GENMASK(2, 1)
> +
> +#define I2C_SR_BUSY			BIT(6)
> +
> +#define I2C_SR_EDEVICE			BIT(1)
> +#define I2C_SR_EDATA			BIT(2)
> +
> +#define I2C_FIFO_MAX			16
> +
> +#define I2C_TIMEOUT			msecs_to_jiffies(1000)
> +
> +struct zx2967_i2c_info {
> +	spinlock_t		lock;
> +	struct device		*dev;
> +	struct i2c_adapter	adap;
> +	struct clk		*clk;
> +	struct completion	complete;
> +	u32			clk_freq;
> +	struct pinctrl		*pin_ctrl;
> +	void __iomem		*reg_base;
> +	size_t			residue;
> +	int			id;

I don't see how this field is being used.

> +	int			irq;
> +	int			msg_rd;
> +	u8			*buf;
> +	u8			access_cnt;
> +	bool			is_suspended;
> +};
> +
> +static void zx2967_i2c_writel(struct zx2967_i2c_info *zx_i2c,
> +			      u32 val, unsigned long reg)
> +{
> +	writel_relaxed(val, zx_i2c->reg_base + reg);
> +}
> +
> +static u32 zx2967_i2c_readl(struct zx2967_i2c_info *zx_i2c, unsigned long reg)
> +{
> +	return readl_relaxed(zx_i2c->reg_base + reg);
> +}
> +
> +static void zx2967_i2c_writesb(struct zx2967_i2c_info *zx_i2c,
> +			       void *data, unsigned long reg, int len)
> +{
> +	writesb(zx_i2c->reg_base + reg, data, len);
> +}
> +
> +static void zx2967_i2c_readsb(struct zx2967_i2c_info *zx_i2c,
> +			      void *data, unsigned long reg, int len)
> +{
> +	readsb(zx_i2c->reg_base + reg, data, len);
> +}
> +
> +static void zx2967_i2c_start_ctrl(struct zx2967_i2c_info *zx_i2c)
> +{
> +	u32 status;
> +	u32 ctl;
> +
> +	status = zx2967_i2c_readl(zx_i2c, REG_STAT);
> +	status |= I2C_IRQ_ACK_CLEAR;
> +	zx2967_i2c_writel(zx_i2c, status, REG_STAT);
> +
> +	ctl = zx2967_i2c_readl(zx_i2c, REG_CMD);
> +	if (zx_i2c->msg_rd)
> +		ctl |= I2C_RW_READ;
> +	else
> +		ctl &= ~I2C_RW_READ;
> +	ctl &= ~I2C_CMB_RW_EN;
> +	ctl |= I2C_START;
> +	zx2967_i2c_writel(zx_i2c, ctl, REG_CMD);
> +}
> +
> +static int zx2967_i2c_flush_fifos(struct zx2967_i2c_info *zx_i2c)
> +{
> +	u32 val;
> +	u32 offset;
> +
> +	if (zx_i2c->msg_rd) {
> +		offset = REG_RDCONF;
> +		val = I2C_RFIFO_RESET;
> +	} else {
> +		offset = REG_WRCONF;
> +		val = I2C_WFIFO_RESET;
> +	}
> +
> +	val |= zx2967_i2c_readl(zx_i2c, offset);
> +	zx2967_i2c_writel(zx_i2c, val, offset);
> +
> +	return 0;
> +}
> +
> +static int zx2967_i2c_empty_rx_fifo(struct zx2967_i2c_info *zx_i2c, u32 size)
> +{
> +	u8  val[I2C_FIFO_MAX] = {0};

We need only one space between 'u8' and 'val'.

> +	int i;
> +
> +	if (size > I2C_FIFO_MAX) {
> +		dev_err(zx_i2c->dev, "fifo size %d over the max value %d\n",
> +			size, I2C_FIFO_MAX);
> +		return -EINVAL;
> +	}
> +
> +	zx2967_i2c_readsb(zx_i2c, val, REG_DATA, size);
> +	for (i = 0; i < size; i++) {
> +		*(zx_i2c->buf++) = val[i];
> +		zx_i2c->residue--;
> +		if (zx_i2c->residue <= 0)
> +			break;
> +	}
> +
> +	barrier();
> +
> +	return 0;
> +}
> +
> +static int zx2967_i2c_fill_tx_fifo(struct zx2967_i2c_info *zx_i2c)
> +{
> +	u8 *buf = zx_i2c->buf;
> +	size_t residue = zx_i2c->residue;
> +
> +	if (residue == 0) {
> +		dev_err(zx_i2c->dev, "residue is %d\n", (int)residue);
> +		return -EINVAL;
> +	}
> +
> +	if (residue <= I2C_FIFO_MAX) {
> +		zx2967_i2c_writesb(zx_i2c, buf, REG_DATA, residue);
> +
> +		/* Again update before writing to FIFO to make sure isr sees. */
> +		zx_i2c->residue = 0;
> +		zx_i2c->buf = NULL;
> +	} else {
> +		zx2967_i2c_writesb(zx_i2c, buf, REG_DATA, I2C_FIFO_MAX);
> +		zx_i2c->residue -= I2C_FIFO_MAX;
> +		zx_i2c->buf += I2C_FIFO_MAX;
> +	}
> +
> +	barrier();
> +
> +	return 0;
> +}
> +
> +static int zx2967_i2c_reset_hardware(struct zx2967_i2c_info *zx_i2c)
> +{
> +	u32 val;
> +	u32 clk_div;
> +	u32 status;
> +
> +	val = I2C_MASTER | I2C_IRQ_MSK_ENABLE;
> +	zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +
> +	clk_div = clk_get_rate(zx_i2c->clk) / zx_i2c->clk_freq - 1;
> +	zx2967_i2c_writel(zx_i2c, clk_div, REG_CLK_DIV_FS);
> +	zx2967_i2c_writel(zx_i2c, clk_div, REG_CLK_DIV_HS);
> +
> +	zx2967_i2c_writel(zx_i2c, I2C_FIFO_MAX - 1, REG_WRCONF);
> +	zx2967_i2c_writel(zx_i2c, I2C_FIFO_MAX - 1, REG_RDCONF);
> +	zx2967_i2c_writel(zx_i2c, 1, REG_RDCONF);
> +
> +	if (zx2967_i2c_flush_fifos(zx_i2c))

zx2967_i2c_flush_fifos() seems to always return 0.

> +		return -ETIMEDOUT;
> +
> +	status = zx2967_i2c_readl(zx_i2c, REG_STAT);
> +	if (status & (I2C_SR_BUSY))

The parentheses is not necessary.

> +		return -EBUSY;
> +	if (status & (I2C_SR_EDEVICE | I2C_SR_EDATA))
> +		return -EIO;
> +
> +	enable_irq(zx_i2c->irq);
> +
> +	return 0;
> +}
> +
> +static void zx2967_i2c_isr_clr(struct zx2967_i2c_info *zx_i2c)
> +{
> +	u32 status;
> +
> +	status = zx2967_i2c_readl(zx_i2c, REG_STAT);
> +	status |= I2C_IRQ_ACK_CLEAR;
> +	zx2967_i2c_writel(zx_i2c, status, REG_STAT);
> +}
> +
> +static irqreturn_t zx2967_i2c_isr(int irq, void *dev_id)
> +{
> +	u32 status;
> +	struct zx2967_i2c_info *zx_i2c = (struct zx2967_i2c_info *)dev_id;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&zx_i2c->lock, flags);
> +
> +	status = zx2967_i2c_readl(zx_i2c, REG_STAT) & I2C_INT_MASK;
> +	zx2967_i2c_isr_clr(zx_i2c);
> +
> +	if (status & I2C_ERROR_MASK) {
> +		spin_unlock_irqrestore(&zx_i2c->lock, flags);
> +		return IRQ_HANDLED;
> +	}
> +
> +	if (status & I2C_TRANS_DONE)
> +		complete(&zx_i2c->complete);
> +
> +	spin_unlock_irqrestore(&zx_i2c->lock, flags);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void zx2967_enable_tenbit(struct zx2967_i2c_info *zx_i2c, __u16 addr)
> +{
> +	u16 val = (addr >> 7) & 0x7;
> +
> +	if (val > 0) {
> +		zx2967_i2c_writel(zx_i2c, val, REG_DEVADDR_H);
> +		val = (zx2967_i2c_readl(zx_i2c, REG_CMD)) | I2C_ADDR_MODE_TEN;
> +		zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +	}
> +}
> +
> +static int
> +zx2967_i2c_xfer_read_bytes(struct zx2967_i2c_info *zx_i2c, u32 bytes)
> +{
> +	unsigned long time_left;
> +
> +	reinit_completion(&zx_i2c->complete);
> +	zx2967_i2c_writel(zx_i2c, bytes - 1, REG_RDCONF);
> +	zx2967_i2c_start_ctrl(zx_i2c);
> +
> +	time_left = wait_for_completion_timeout(&zx_i2c->complete,
> +				I2C_TIMEOUT);
> +	if (time_left == 0) {
> +		dev_err(zx_i2c->dev, "read i2c transfer timed out\n");
> +		disable_irq(zx_i2c->irq);
> +		zx2967_i2c_reset_hardware(zx_i2c);
> +		return -EIO;
> +	}
> +
> +	zx2967_i2c_empty_rx_fifo(zx_i2c, bytes);

The function could return error.

> +	return 0;
> +}
> +
> +static int zx2967_i2c_xfer_read(struct zx2967_i2c_info *zx_i2c)
> +{
> +	int ret;
> +	int i;
> +
> +	for (i = 0; i < zx_i2c->access_cnt; i++) {
> +		ret = zx2967_i2c_xfer_read_bytes(zx_i2c, I2C_FIFO_MAX);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (zx_i2c->residue > 0) {
> +		ret = zx2967_i2c_xfer_read_bytes(zx_i2c, I2C_FIFO_MAX);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	zx_i2c->residue = 0;
> +	zx_i2c->access_cnt = 0;
> +	return 0;
> +}
> +
> +static int
> +zx2967_i2c_xfer_write_bytes(struct zx2967_i2c_info *zx_i2c, u32 bytes)
> +{
> +	unsigned long time_left;
> +
> +	reinit_completion(&zx_i2c->complete);
> +	zx2967_i2c_fill_tx_fifo(zx_i2c);

It could return error.

> +	zx2967_i2c_start_ctrl(zx_i2c);
> +
> +	time_left = wait_for_completion_timeout(&zx_i2c->complete,
> +				I2C_TIMEOUT);
> +	if (time_left == 0) {
> +		dev_err(zx_i2c->dev, "write i2c transfer timed out\n");
> +		disable_irq(zx_i2c->irq);
> +		zx2967_i2c_reset_hardware(zx_i2c);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static int zx2967_i2c_xfer_write(struct zx2967_i2c_info *zx_i2c)
> +{
> +	int ret;
> +	int i;
> +
> +	for (i = 0; i < zx_i2c->access_cnt; i++) {
> +		ret = zx2967_i2c_xfer_write_bytes(zx_i2c, I2C_FIFO_MAX);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (zx_i2c->residue > 0) {
> +		ret = zx2967_i2c_xfer_write_bytes(zx_i2c, I2C_FIFO_MAX);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	zx_i2c->residue = 0;
> +	zx_i2c->access_cnt = 0;
> +	return 0;
> +}
> +
> +static int zx2967_i2c_xfer_msg(struct zx2967_i2c_info *zx_i2c,
> +			       struct i2c_msg *msg)
> +{
> +	if (msg->len == 0)
> +		return -EINVAL;
> +
> +	zx2967_i2c_flush_fifos(zx_i2c);
> +
> +	zx_i2c->buf = msg->buf;
> +	zx_i2c->residue = msg->len;
> +	zx_i2c->access_cnt = msg->len / I2C_FIFO_MAX;
> +	zx_i2c->msg_rd = (msg->flags & I2C_M_RD);
> +
> +	if (zx_i2c->msg_rd)
> +		return zx2967_i2c_xfer_read(zx_i2c);
> +
> +	return zx2967_i2c_xfer_write(zx_i2c);
> +}
> +
> +static int zx2967_i2c_xfer(struct i2c_adapter *adap,
> +			   struct i2c_msg *msgs, int num)
> +{
> +	struct zx2967_i2c_info *zx_i2c = i2c_get_adapdata(adap);
> +	int ret;
> +	int i;
> +
> +	if (zx_i2c->is_suspended)
> +		return -EBUSY;
> +
> +	zx2967_i2c_writel(zx_i2c, (msgs->addr & 0x7f), REG_DEVADDR_L);
> +	zx2967_i2c_writel(zx_i2c, (msgs->addr >> 7) & 0x7, REG_DEVADDR_H);
> +	if (zx2967_i2c_readl(zx_i2c, REG_DEVADDR_H) > 0)
> +		zx2967_enable_tenbit(zx_i2c, msgs->addr);
> +
> +	for (i = 0; i < num; i++) {
> +		ret = zx2967_i2c_xfer_msg(zx_i2c, &msgs[i]);
> +		if (num > 1)
> +			usleep_range(1000, 2000);
> +		if (ret)
> +			return ret;

The 'ret' check should probably be put before usleep_range check?

> +	}
> +
> +	return num;
> +}
> +
> +static void
> +zx2967_smbus_xfer_prepare(struct zx2967_i2c_info *zx_i2c, u16 addr,
> +			  char read_write, u8 command, int size,
> +			  union i2c_smbus_data *data)
> +{
> +	u32 val;
> +
> +	val = zx2967_i2c_readl(zx_i2c, REG_RDCONF);
> +	val |= I2C_RFIFO_RESET;
> +	zx2967_i2c_writel(zx_i2c, val, REG_RDCONF);
> +	zx2967_i2c_writel(zx_i2c, (addr & 0x7f), REG_DEVADDR_L);
> +
> +	zx2967_enable_tenbit(zx_i2c, addr);
> +	val = zx2967_i2c_readl(zx_i2c, REG_CMD);
> +	val &= ~I2C_RW_READ;
> +	zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +
> +	switch (size) {
> +	case I2C_SMBUS_BYTE:
> +		zx2967_i2c_writel(zx_i2c, command, REG_DATA);
> +		break;
> +	case I2C_SMBUS_BYTE_DATA:
> +		zx2967_i2c_writel(zx_i2c, command, REG_DATA);
> +		if (read_write == I2C_SMBUS_WRITE)
> +			zx2967_i2c_writel(zx_i2c, data->byte, REG_DATA);
> +		break;
> +	case I2C_SMBUS_WORD_DATA:
> +		zx2967_i2c_writel(zx_i2c, command, REG_DATA);
> +		if (read_write == I2C_SMBUS_WRITE) {
> +			zx2967_i2c_writel(zx_i2c, (data->word >> 8), REG_DATA);
> +			zx2967_i2c_writel(zx_i2c, (data->word & 0xff),
> +					  REG_DATA);
> +		}
> +		break;
> +	}
> +}
> +
> +static int zx2967_smbus_xfer_read(struct zx2967_i2c_info *zx_i2c, int size,
> +				  union i2c_smbus_data *data)
> +{
> +	unsigned long time_left;
> +	u8 buf[2];
> +	u32 val;
> +
> +	reinit_completion(&zx_i2c->complete);
> +
> +	val = zx2967_i2c_readl(zx_i2c, REG_CMD);
> +	val |= I2C_CMB_RW_EN;
> +	zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +
> +	val = zx2967_i2c_readl(zx_i2c, REG_CMD);
> +	val |= I2C_START;
> +	zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +
> +	time_left = wait_for_completion_timeout(&zx_i2c->complete,
> +						I2C_TIMEOUT);
> +	if (time_left == 0) {
> +		dev_err(zx_i2c->dev, "i2c read transfer timed out\n");
> +		disable_irq(zx_i2c->irq);
> +		zx2967_i2c_reset_hardware(zx_i2c);
> +		return -EIO;
> +	}
> +
> +	usleep_range(1000, 2000);
> +	switch (size) {
> +	case I2C_SMBUS_BYTE:
> +	case I2C_SMBUS_BYTE_DATA:
> +		val = zx2967_i2c_readl(zx_i2c, REG_DATA);
> +		data->byte = val;
> +		break;
> +	case I2C_SMBUS_WORD_DATA:
> +	case I2C_SMBUS_PROC_CALL:
> +		buf[0] = zx2967_i2c_readl(zx_i2c, REG_DATA);
> +		buf[1] = zx2967_i2c_readl(zx_i2c, REG_DATA);
> +		data->word = (buf[0] << 8) | buf[1];
> +		break;
> +	default:
> +		dev_warn(zx_i2c->dev, "Unsupported transaction %d\n", size);
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static int zx2967_smbus_xfer_write(struct zx2967_i2c_info *zx_i2c)
> +{
> +	unsigned long time_left;
> +	u32 val;
> +
> +	reinit_completion(&zx_i2c->complete);
> +	val = zx2967_i2c_readl(zx_i2c, REG_CMD);
> +	val |= I2C_START;
> +	zx2967_i2c_writel(zx_i2c, val, REG_CMD);
> +
> +	time_left = wait_for_completion_timeout(&zx_i2c->complete,
> +						I2C_TIMEOUT);
> +	if (time_left == 0) {
> +		dev_err(zx_i2c->dev, "i2c write transfer timed out\n");
> +		disable_irq(zx_i2c->irq);
> +		zx2967_i2c_reset_hardware(zx_i2c);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static int zx2967_smbus_xfer(struct i2c_adapter *adap, u16 addr,
> +			     unsigned short flags, char read_write,
> +			     u8 command, int size, union i2c_smbus_data *data)
> +{
> +	struct zx2967_i2c_info *zx_i2c = i2c_get_adapdata(adap);
> +
> +	if (size == I2C_SMBUS_QUICK)
> +		read_write = I2C_SMBUS_WRITE;
> +
> +	switch (size) {
> +	case I2C_SMBUS_QUICK:
> +	case I2C_SMBUS_BYTE:
> +	case I2C_SMBUS_BYTE_DATA:
> +	case I2C_SMBUS_WORD_DATA:
> +		zx2967_smbus_xfer_prepare(zx_i2c, addr, read_write,
> +					  command, size, data);
> +		break;
> +	default:
> +		dev_warn(&adap->dev, "Unsupported transaction %d\n", size);
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (read_write == I2C_SMBUS_READ)
> +		return zx2967_smbus_xfer_read(zx_i2c, size, data);
> +
> +	return zx2967_smbus_xfer_write(zx_i2c);
> +}
> +
> +#define ZX2967_I2C_FUNCS (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |	\
> +		I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |	\
> +		I2C_FUNC_SMBUS_BLOCK_DATA | I2C_FUNC_SMBUS_PROC_CALL |	\
> +		I2C_FUNC_I2C | I2C_FUNC_SMBUS_I2C_BLOCK)

Have a newline here.

> +static u32 zx2967_i2c_func(struct i2c_adapter *adap)
> +{
> +	return ZX2967_I2C_FUNCS;
> +}
> +
> +static int __maybe_unused zx2967_i2c_suspend(struct device *dev)
> +{
> +	struct zx2967_i2c_info *zx_i2c = dev_get_drvdata(dev);
> +
> +	zx_i2c->is_suspended = true;
> +	if (__clk_get_enable_count(zx_i2c->clk) == 1)
> +		clk_disable_unprepare(zx_i2c->clk);

clk_prepare_enable() and clk_disable_unprepare() should always be called
in a balanced way.  In that case,  you shouldn't need to check enable
count.

> +
> +	return 0;
> +}
> +
> +static int __maybe_unused zx2967_i2c_resume(struct device *dev)
> +{
> +	struct zx2967_i2c_info *zx_i2c = dev_get_drvdata(dev);
> +
> +	zx_i2c->is_suspended = false;
> +	clk_prepare_enable(zx_i2c->clk);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static const struct dev_pm_ops zx2967_i2c_dev_pm_ops = {
> +	.suspend	= zx2967_i2c_suspend,
> +	.resume		= zx2967_i2c_resume,
> +};
> +#define ZX2967_I2C_DEV_PM_OPS	(&zx2967_i2c_dev_pm_ops)
> +#else
> +#define	ZX2967_I2C_DEV_PM_OPS	NULL
> +#endif
> +
> +static const struct i2c_algorithm zx2967_i2c_algo = {
> +	.master_xfer = zx2967_i2c_xfer,
> +	.smbus_xfer = zx2967_smbus_xfer,
> +	.functionality = zx2967_i2c_func,
> +};
> +
> +static const struct of_device_id zx2967_i2c_of_match[] = {
> +	{ .compatible = "zte,zx296718-i2c", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, zx2967_i2c_of_match);
> +
> +static int zx2967_i2c_probe(struct platform_device *pdev)
> +{
> +	struct zx2967_i2c_info *zx_i2c;
> +	void __iomem *reg_base;
> +	struct resource *res;
> +	struct clk *clk;
> +	int ret;
> +
> +	zx_i2c = devm_kzalloc(&pdev->dev, sizeof(*zx_i2c), GFP_KERNEL);
> +	if (!zx_i2c)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	reg_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(reg_base))
> +		return PTR_ERR(reg_base);
> +
> +	clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(clk)) {
> +		dev_err(&pdev->dev, "missing controller clock");
> +		return PTR_ERR(clk);
> +	}
> +
> +	ret = clk_prepare_enable(clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to enable i2c_clk\n");
> +		return ret;
> +	}
> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		return ret;
> +	zx_i2c->irq = ret;
> +
> +	device_property_read_u32(&pdev->dev, "clock-frequency",
> +				 &zx_i2c->clk_freq);

Since you list it in bindings doc as a required property, shouldn't you
check the return of the call to make sure the property is found
successfully?

> +	zx_i2c->reg_base = reg_base;
> +	zx_i2c->clk = clk;
> +	zx_i2c->id = pdev->id;
> +	zx_i2c->dev = &pdev->dev;
> +
> +	zx_i2c->pin_ctrl = devm_pinctrl_get_select(&pdev->dev, "pinctrl-0");
> +	if (IS_ERR(zx_i2c->pin_ctrl))
> +		dev_info(&pdev->dev, "pinctrl-0 pin is not specified in dts\n");

It seems that I did not make my comment clear on the previous version.
I was trying to say you do not need to explicitly call pinctrl function,
if what you need is just to request 'default' pin state.  Take a look at
commit ab78029ecc34 ("drivers/pinctrl: grab default handles from device
core"), and you will know what I'm saying.

Shawn

> +
> +	spin_lock_init(&zx_i2c->lock);
> +	init_completion(&zx_i2c->complete);
> +	platform_set_drvdata(pdev, zx_i2c);
> +
> +	ret = zx2967_i2c_reset_hardware(zx_i2c);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to initialize i2c controller\n");
> +		goto err_clk_unprepare;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, zx_i2c->irq,
> +			zx2967_i2c_isr, 0, dev_name(&pdev->dev), zx_i2c);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to request irq %i\n", zx_i2c->irq);
> +		goto err_clk_unprepare;
> +	}
> +
> +	i2c_set_adapdata(&zx_i2c->adap, zx_i2c);
> +	zx_i2c->adap.owner = THIS_MODULE;
> +	zx_i2c->adap.class = I2C_CLASS_DEPRECATED;
> +	strlcpy(zx_i2c->adap.name, "zx2967 i2c adapter",
> +		sizeof(zx_i2c->adap.name));
> +	zx_i2c->adap.algo = &zx2967_i2c_algo;
> +	zx_i2c->adap.dev.parent = &pdev->dev;
> +	zx_i2c->adap.nr = pdev->id;
> +	zx_i2c->adap.dev.of_node = pdev->dev.of_node;
> +
> +	ret = i2c_add_numbered_adapter(&zx_i2c->adap);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to add zx2967 i2c adapter\n");
> +		goto err_clk_unprepare;
> +	}
> +
> +	return 0;
> +
> +err_clk_unprepare:
> +	clk_disable_unprepare(zx_i2c->clk);
> +	return ret;
> +}
> +
> +static int zx2967_i2c_remove(struct platform_device *pdev)
> +{
> +	struct zx2967_i2c_info *zx_i2c = platform_get_drvdata(pdev);
> +
> +	i2c_del_adapter(&zx_i2c->adap);
> +	clk_disable_unprepare(zx_i2c->clk);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver zx2967_i2c_driver = {
> +	.probe	= zx2967_i2c_probe,
> +	.remove	= zx2967_i2c_remove,
> +	.driver	= {
> +		.name  = "zx2967_i2c",
> +		.of_match_table = zx2967_i2c_of_match,
> +		.pm		= ZX2967_I2C_DEV_PM_OPS,
> +	},
> +};
> +module_platform_driver(zx2967_i2c_driver);
> +
> +MODULE_AUTHOR("Baoyou Xie <baoyou.xie@...aro.org>");
> +MODULE_DESCRIPTION("ZTE zx2967 I2C Bus Controller driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.7.4
> 

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