Commit 0daede80 authored by Serge Semin's avatar Serge Semin Committed by Wolfram Sang
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i2c: designware: Convert driver to using regmap API



Seeing the DW I2C driver is using flags-based accessors with two
conditional clauses it would be better to replace them with the regmap
API IO methods and to initialize the regmap object with read/write
callbacks specific to the controller registers map implementation. This
will be also handy for the drivers with non-standard registers mapping
(like an embedded into the Baikal-T1 System Controller DW I2C block, which
glue-driver is a part of this series).

As before the driver tries to detect the mapping setup at probe stage and
creates a regmap object accordingly, which will be used by the rest of the
code to correctly access the controller registers. In two places it was
appropriate to convert the hand-written read-modify-write and
read-poll-loop design patterns to the corresponding regmap API
ready-to-use methods.

Note the regmap IO methods return value is checked only at the probe
stage. The rest of the code won't do this because basically we have
MMIO-based regmap so non of the read/write methods can fail (this also
won't be needed for the Baikal-T1-specific I2C controller).

Suggested-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarSerge Semin <Sergey.Semin@baikalelectronics.ru>
Tested-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
[wsa: fix type of 'rx_valid' and remove outdated kdoc var description]
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent c615f5c6
......@@ -526,6 +526,7 @@ config I2C_DAVINCI
config I2C_DESIGNWARE_CORE
tristate
select REGMAP
config I2C_DESIGNWARE_SLAVE
bool "Synopsys DesignWare Slave"
......
......@@ -21,6 +21,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/swab.h>
#include <linux/types.h>
......@@ -57,66 +58,122 @@ static char *abort_sources[] = {
"incorrect slave-transmitter mode configuration",
};
u32 dw_readl(struct dw_i2c_dev *dev, int offset)
static int dw_reg_read(void *context, unsigned int reg, unsigned int *val)
{
u32 value;
struct dw_i2c_dev *dev = context;
if (dev->flags & ACCESS_16BIT)
value = readw_relaxed(dev->base + offset) |
(readw_relaxed(dev->base + offset + 2) << 16);
else
value = readl_relaxed(dev->base + offset);
*val = readl_relaxed(dev->base + reg);
if (dev->flags & ACCESS_SWAP)
return swab32(value);
else
return value;
return 0;
}
void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset)
static int dw_reg_write(void *context, unsigned int reg, unsigned int val)
{
if (dev->flags & ACCESS_SWAP)
b = swab32(b);
if (dev->flags & ACCESS_16BIT) {
writew_relaxed((u16)b, dev->base + offset);
writew_relaxed((u16)(b >> 16), dev->base + offset + 2);
} else {
writel_relaxed(b, dev->base + offset);
}
struct dw_i2c_dev *dev = context;
writel_relaxed(val, dev->base + reg);
return 0;
}
static int dw_reg_read_swab(void *context, unsigned int reg, unsigned int *val)
{
struct dw_i2c_dev *dev = context;
*val = swab32(readl_relaxed(dev->base + reg));
return 0;
}
static int dw_reg_write_swab(void *context, unsigned int reg, unsigned int val)
{
struct dw_i2c_dev *dev = context;
writel_relaxed(swab32(val), dev->base + reg);
return 0;
}
static int dw_reg_read_word(void *context, unsigned int reg, unsigned int *val)
{
struct dw_i2c_dev *dev = context;
*val = readw_relaxed(dev->base + reg) |
(readw_relaxed(dev->base + reg + 2) << 16);
return 0;
}
static int dw_reg_write_word(void *context, unsigned int reg, unsigned int val)
{
struct dw_i2c_dev *dev = context;
writew_relaxed(val, dev->base + reg);
writew_relaxed(val >> 16, dev->base + reg + 2);
return 0;
}
/**
* i2c_dw_set_reg_access() - Set register access flags
* i2c_dw_init_regmap() - Initialize registers map
* @dev: device private data
*
* Autodetects needed register access mode and sets access flags accordingly.
* This must be called before doing any other register access.
* Autodetects needed register access mode and creates the regmap with
* corresponding read/write callbacks. This must be called before doing any
* other register access.
*/
int i2c_dw_set_reg_access(struct dw_i2c_dev *dev)
int i2c_dw_init_regmap(struct dw_i2c_dev *dev)
{
struct regmap_config map_cfg = {
.reg_bits = 32,
.val_bits = 32,
.reg_stride = 4,
.disable_locking = true,
.reg_read = dw_reg_read,
.reg_write = dw_reg_write,
.max_register = DW_IC_COMP_TYPE,
};
u32 reg;
int ret;
/*
* Skip detecting the registers map configuration if the regmap has
* already been provided by a higher code.
*/
if (dev->map)
return 0;
ret = i2c_dw_acquire_lock(dev);
if (ret)
return ret;
reg = dw_readl(dev, DW_IC_COMP_TYPE);
reg = readl(dev->base + DW_IC_COMP_TYPE);
i2c_dw_release_lock(dev);
if (reg == swab32(DW_IC_COMP_TYPE_VALUE)) {
/* Configure register endianness access */
dev->flags |= ACCESS_SWAP;
map_cfg.reg_read = dw_reg_read_swab;
map_cfg.reg_write = dw_reg_write_swab;
} else if (reg == (DW_IC_COMP_TYPE_VALUE & 0x0000ffff)) {
/* Configure register access mode 16bit */
dev->flags |= ACCESS_16BIT;
map_cfg.reg_read = dw_reg_read_word;
map_cfg.reg_write = dw_reg_write_word;
} else if (reg != DW_IC_COMP_TYPE_VALUE) {
dev_err(dev->dev,
"Unknown Synopsys component type: 0x%08x\n", reg);
return -ENODEV;
}
/*
* Note we'll check the return value of the regmap IO accessors only
* at the probe stage. The rest of the code won't do this because
* basically we have MMIO-based regmap so non of the read/write methods
* can fail.
*/
dev->map = devm_regmap_init(dev->dev, NULL, dev, &map_cfg);
if (IS_ERR(dev->map)) {
dev_err(dev->dev, "Failed to init the registers map\n");
return PTR_ERR(dev->map);
}
return 0;
}
......@@ -327,11 +384,17 @@ int i2c_dw_set_sda_hold(struct dw_i2c_dev *dev)
return ret;
/* Configure SDA Hold Time if required */
reg = dw_readl(dev, DW_IC_COMP_VERSION);
ret = regmap_read(dev->map, DW_IC_COMP_VERSION, &reg);
if (ret)
goto err_release_lock;
if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
if (!dev->sda_hold_time) {
/* Keep previous hold time setting if no one set it */
dev->sda_hold_time = dw_readl(dev, DW_IC_SDA_HOLD);
ret = regmap_read(dev->map, DW_IC_SDA_HOLD,
&dev->sda_hold_time);
if (ret)
goto err_release_lock;
}
/*
......@@ -355,14 +418,16 @@ int i2c_dw_set_sda_hold(struct dw_i2c_dev *dev)
dev->sda_hold_time = 0;
}
err_release_lock:
i2c_dw_release_lock(dev);
return 0;
return ret;
}
void __i2c_dw_disable(struct dw_i2c_dev *dev)
{
int timeout = 100;
u32 status;
do {
__i2c_dw_disable_nowait(dev);
......@@ -370,7 +435,8 @@ void __i2c_dw_disable(struct dw_i2c_dev *dev)
* The enable status register may be unimplemented, but
* in that case this test reads zero and exits the loop.
*/
if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == 0)
regmap_read(dev->map, DW_IC_ENABLE_STATUS, &status);
if ((status & 1) == 0)
return;
/*
......@@ -449,22 +515,23 @@ void i2c_dw_release_lock(struct dw_i2c_dev *dev)
*/
int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev)
{
int timeout = TIMEOUT;
u32 status;
int ret;
while (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
if (timeout <= 0) {
dev_warn(dev->dev, "timeout waiting for bus ready\n");
i2c_recover_bus(&dev->adapter);
ret = regmap_read_poll_timeout(dev->map, DW_IC_STATUS, status,
!(status & DW_IC_STATUS_ACTIVITY),
1100, 20000);
if (ret) {
dev_warn(dev->dev, "timeout waiting for bus ready\n");
if (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY)
return -ETIMEDOUT;
return 0;
}
timeout--;
usleep_range(1000, 1100);
i2c_recover_bus(&dev->adapter);
regmap_read(dev->map, DW_IC_STATUS, &status);
if (!(status & DW_IC_STATUS_ACTIVITY))
ret = 0;
}
return 0;
return ret;
}
int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev)
......@@ -490,15 +557,19 @@ int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev)
return -EIO;
}
void i2c_dw_set_fifo_size(struct dw_i2c_dev *dev)
int i2c_dw_set_fifo_size(struct dw_i2c_dev *dev)
{
u32 param, tx_fifo_depth, rx_fifo_depth;
int ret;
/*
* Try to detect the FIFO depth if not set by interface driver,
* the depth could be from 2 to 256 from HW spec.
*/
param = dw_readl(dev, DW_IC_COMP_PARAM_1);
ret = regmap_read(dev->map, DW_IC_COMP_PARAM_1, &param);
if (ret)
return ret;
tx_fifo_depth = ((param >> 16) & 0xff) + 1;
rx_fifo_depth = ((param >> 8) & 0xff) + 1;
if (!dev->tx_fifo_depth) {
......@@ -510,6 +581,8 @@ void i2c_dw_set_fifo_size(struct dw_i2c_dev *dev)
dev->rx_fifo_depth = min_t(u32, dev->rx_fifo_depth,
rx_fifo_depth);
}
return 0;
}
u32 i2c_dw_func(struct i2c_adapter *adap)
......@@ -521,17 +594,19 @@ u32 i2c_dw_func(struct i2c_adapter *adap)
void i2c_dw_disable(struct dw_i2c_dev *dev)
{
u32 dummy;
/* Disable controller */
__i2c_dw_disable(dev);
/* Disable all interrupts */
dw_writel(dev, 0, DW_IC_INTR_MASK);
dw_readl(dev, DW_IC_CLR_INTR);
regmap_write(dev->map, DW_IC_INTR_MASK, 0);
regmap_read(dev->map, DW_IC_CLR_INTR, &dummy);
}
void i2c_dw_disable_int(struct dw_i2c_dev *dev)
{
dw_writel(dev, 0, DW_IC_INTR_MASK);
regmap_write(dev->map, DW_IC_INTR_MASK, 0);
}
MODULE_DESCRIPTION("Synopsys DesignWare I2C bus adapter core");
......
......@@ -15,6 +15,7 @@
#include <linux/dev_printk.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/regmap.h>
#include <linux/types.h>
#define DW_IC_DEFAULT_FUNCTIONALITY (I2C_FUNC_I2C | \
......@@ -126,8 +127,6 @@
#define STATUS_WRITE_IN_PROGRESS 0x1
#define STATUS_READ_IN_PROGRESS 0x2
#define TIMEOUT 20 /* ms */
/*
* operation modes
*/
......@@ -183,7 +182,9 @@ struct reset_control;
/**
* struct dw_i2c_dev - private i2c-designware data
* @dev: driver model device node
* @map: IO registers map
* @base: IO registers pointer
* @ext: Extended IO registers pointer
* @cmd_complete: tx completion indicator
* @clk: input reference clock
* @pclk: clock required to access the registers
......@@ -233,6 +234,7 @@ struct reset_control;
*/
struct dw_i2c_dev {
struct device *dev;
struct regmap *map;
void __iomem *base;
void __iomem *ext;
struct completion cmd_complete;
......@@ -284,17 +286,13 @@ struct dw_i2c_dev {
bool suspended;
};
#define ACCESS_SWAP 0x00000001
#define ACCESS_16BIT 0x00000002
#define ACCESS_INTR_MASK 0x00000004
#define ACCESS_NO_IRQ_SUSPEND 0x00000008
#define ACCESS_INTR_MASK 0x00000001
#define ACCESS_NO_IRQ_SUSPEND 0x00000002
#define MODEL_MSCC_OCELOT 0x00000100
#define MODEL_MASK 0x00000f00
u32 dw_readl(struct dw_i2c_dev *dev, int offset);
void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset);
int i2c_dw_set_reg_access(struct dw_i2c_dev *dev);
int i2c_dw_init_regmap(struct dw_i2c_dev *dev);
u32 i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset);
u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset);
int i2c_dw_set_sda_hold(struct dw_i2c_dev *dev);
......@@ -304,19 +302,19 @@ int i2c_dw_acquire_lock(struct dw_i2c_dev *dev);
void i2c_dw_release_lock(struct dw_i2c_dev *dev);
int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev);
int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev);
void i2c_dw_set_fifo_size(struct dw_i2c_dev *dev);
int i2c_dw_set_fifo_size(struct dw_i2c_dev *dev);
u32 i2c_dw_func(struct i2c_adapter *adap);
void i2c_dw_disable(struct dw_i2c_dev *dev);
void i2c_dw_disable_int(struct dw_i2c_dev *dev);
static inline void __i2c_dw_enable(struct dw_i2c_dev *dev)
{
dw_writel(dev, 1, DW_IC_ENABLE);
regmap_write(dev->map, DW_IC_ENABLE, 1);
}
static inline void __i2c_dw_disable_nowait(struct dw_i2c_dev *dev)
{
dw_writel(dev, 0, DW_IC_ENABLE);
regmap_write(dev->map, DW_IC_ENABLE, 0);
}
void __i2c_dw_disable(struct dw_i2c_dev *dev);
......
......@@ -18,6 +18,7 @@
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/reset.h>
#include "i2c-designware-core.h"
......@@ -25,11 +26,11 @@
static void i2c_dw_configure_fifo_master(struct dw_i2c_dev *dev)
{
/* Configure Tx/Rx FIFO threshold levels */
dw_writel(dev, dev->tx_fifo_depth / 2, DW_IC_TX_TL);
dw_writel(dev, 0, DW_IC_RX_TL);
regmap_write(dev->map, DW_IC_TX_TL, dev->tx_fifo_depth / 2);
regmap_write(dev->map, DW_IC_RX_TL, 0);
/* Configure the I2C master */
dw_writel(dev, dev->master_cfg, DW_IC_CON);
regmap_write(dev->map, DW_IC_CON, dev->master_cfg);
}
static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
......@@ -44,8 +45,11 @@ static int i2c_dw_set_timings_master(struct dw_i2c_dev *dev)
ret = i2c_dw_acquire_lock(dev);
if (ret)
return ret;
comp_param1 = dw_readl(dev, DW_IC_COMP_PARAM_1);
ret = regmap_read(dev->map, DW_IC_COMP_PARAM_1, &comp_param1);
i2c_dw_release_lock(dev);
if (ret)
return ret;
/* Set standard and fast speed dividers for high/low periods */
sda_falling_time = t->sda_fall_ns ?: 300; /* ns */
......@@ -187,22 +191,22 @@ static int i2c_dw_init_master(struct dw_i2c_dev *dev)
__i2c_dw_disable(dev);
/* Write standard speed timing parameters */
dw_writel(dev, dev->ss_hcnt, DW_IC_SS_SCL_HCNT);
dw_writel(dev, dev->ss_lcnt, DW_IC_SS_SCL_LCNT);
regmap_write(dev->map, DW_IC_SS_SCL_HCNT, dev->ss_hcnt);
regmap_write(dev->map, DW_IC_SS_SCL_LCNT, dev->ss_lcnt);
/* Write fast mode/fast mode plus timing parameters */
dw_writel(dev, dev->fs_hcnt, DW_IC_FS_SCL_HCNT);
dw_writel(dev, dev->fs_lcnt, DW_IC_FS_SCL_LCNT);
regmap_write(dev->map, DW_IC_FS_SCL_HCNT, dev->fs_hcnt);
regmap_write(dev->map, DW_IC_FS_SCL_LCNT, dev->fs_lcnt);
/* Write high speed timing parameters if supported */
if (dev->hs_hcnt && dev->hs_lcnt) {
dw_writel(dev, dev->hs_hcnt, DW_IC_HS_SCL_HCNT);
dw_writel(dev, dev->hs_lcnt, DW_IC_HS_SCL_LCNT);
regmap_write(dev->map, DW_IC_HS_SCL_HCNT, dev->hs_hcnt);
regmap_write(dev->map, DW_IC_HS_SCL_LCNT, dev->hs_lcnt);
}
/* Write SDA hold time if supported */
if (dev->sda_hold_time)
dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
regmap_write(dev->map, DW_IC_SDA_HOLD, dev->sda_hold_time);
i2c_dw_configure_fifo_master(dev);
i2c_dw_release_lock(dev);
......@@ -213,15 +217,15 @@ static int i2c_dw_init_master(struct dw_i2c_dev *dev)
static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
{
struct i2c_msg *msgs = dev->msgs;
u32 ic_con, ic_tar = 0;
u32 ic_con = 0, ic_tar = 0;
u32 dummy;
/* Disable the adapter */
__i2c_dw_disable(dev);
/* If the slave address is ten bit address, enable 10BITADDR */
ic_con = dw_readl(dev, DW_IC_CON);
if (msgs[dev->msg_write_idx].flags & I2C_M_TEN) {
ic_con |= DW_IC_CON_10BITADDR_MASTER;
ic_con = DW_IC_CON_10BITADDR_MASTER;
/*
* If I2C_DYNAMIC_TAR_UPDATE is set, the 10-bit addressing
* mode has to be enabled via bit 12 of IC_TAR register.
......@@ -229,17 +233,17 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
* detected from registers.
*/
ic_tar = DW_IC_TAR_10BITADDR_MASTER;
} else {
ic_con &= ~DW_IC_CON_10BITADDR_MASTER;
}
dw_writel(dev, ic_con, DW_IC_CON);
regmap_update_bits(dev->map, DW_IC_CON, DW_IC_CON_10BITADDR_MASTER,
ic_con);
/*
* Set the slave (target) address and enable 10-bit addressing mode
* if applicable.
*/
dw_writel(dev, msgs[dev->msg_write_idx].addr | ic_tar, DW_IC_TAR);
regmap_write(dev->map, DW_IC_TAR,
msgs[dev->msg_write_idx].addr | ic_tar);
/* Enforce disabled interrupts (due to HW issues) */
i2c_dw_disable_int(dev);
......@@ -248,11 +252,11 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
__i2c_dw_enable(dev);
/* Dummy read to avoid the register getting stuck on Bay Trail */
dw_readl(dev, DW_IC_ENABLE_STATUS);
regmap_read(dev->map, DW_IC_ENABLE_STATUS, &dummy);
/* Clear and enable interrupts */
dw_readl(dev, DW_IC_CLR_INTR);
dw_writel(dev, DW_IC_INTR_MASTER_MASK, DW_IC_INTR_MASK);
regmap_read(dev->map, DW_IC_CLR_INTR, &dummy);
regmap_write(dev->map, DW_IC_INTR_MASK, DW_IC_INTR_MASTER_MASK);
}
/*
......@@ -271,6 +275,7 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
u32 buf_len = dev->tx_buf_len;
u8 *buf = dev->tx_buf;
bool need_restart = false;
unsigned int flr;
intr_mask = DW_IC_INTR_MASTER_MASK;
......@@ -303,8 +308,11 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
need_restart = true;
}
tx_limit = dev->tx_fifo_depth - dw_readl(dev, DW_IC_TXFLR);
rx_limit = dev->rx_fifo_depth - dw_readl(dev, DW_IC_RXFLR);
regmap_read(dev->map, DW_IC_TXFLR, &flr);
tx_limit = dev->tx_fifo_depth - flr;
regmap_read(dev->map, DW_IC_RXFLR, &flr);
rx_limit = dev->rx_fifo_depth - flr;
while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
u32 cmd = 0;
......@@ -337,11 +345,14 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
if (dev->rx_outstanding >= dev->rx_fifo_depth)
break;
dw_writel(dev, cmd | 0x100, DW_IC_DATA_CMD);
regmap_write(dev->map, DW_IC_DATA_CMD,
cmd | 0x100);
rx_limit--;
dev->rx_outstanding++;
} else
dw_writel(dev, cmd | *buf++, DW_IC_DATA_CMD);
} else {
regmap_write(dev->map, DW_IC_DATA_CMD,
cmd | *buf++);
}
tx_limit--; buf_len--;
}
......@@ -371,7 +382,7 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
if (dev->msg_err)
intr_mask = 0;
dw_writel(dev, intr_mask, DW_IC_INTR_MASK);
regmap_write(dev->map, DW_IC_INTR_MASK, intr_mask);
}
static u8
......@@ -396,10 +407,10 @@ static void
i2c_dw_read(struct dw_i2c_dev *dev)
{
struct i2c_msg *msgs = dev->msgs;
int rx_valid;
unsigned int rx_valid;
for (; dev->msg_read_idx < dev->msgs_num; dev->msg_read_idx++) {
u32 len;
u32 len, tmp;
u8 *buf;
if (!(msgs[dev->msg_read_idx].flags & I2C_M_RD))
......@@ -413,18 +424,18 @@ i2c_dw_read(struct dw_i2c_dev *dev)
buf = dev->rx_buf;
}
rx_valid = dw_readl(dev, DW_IC_RXFLR);
regmap_read(dev->map, DW_IC_RXFLR, &rx_valid);
for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
u32 flags = msgs[dev->msg_read_idx].flags;
*buf = dw_readl(dev, DW_IC_DATA_CMD);
regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
/* Ensure length byte is a valid value */
if (flags & I2C_M_RECV_LEN &&
*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0) {
len = i2c_dw_recv_len(dev, *buf);
tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
len = i2c_dw_recv_len(dev, tmp);
}
buf++;
*buf++ = tmp;
dev->rx_outstanding--;
}
......@@ -542,7 +553,7 @@ static const struct i2c_adapter_quirks i2c_dw_quirks = {
static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
{
u32 stat;
u32 stat, dummy;
/*
* The IC_INTR_STAT register just indicates "enabled" interrupts.
......@@ -550,47 +561,47 @@ static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
* in the IC_RAW_INTR_STAT register.
*
* That is,
* stat = dw_readl(IC_INTR_STAT);
* stat = readl(IC_INTR_STAT);
* equals to,
* stat = dw_readl(IC_RAW_INTR_STAT) & dw_readl(IC_INTR_MASK);
* stat = readl(IC_RAW_INTR_STAT) & readl(IC_INTR_MASK);
*