[PATCH v5 3/9] rtc: abx80x: add mutex protection for register writes
From: Antoni Pokusinski
Date: Tue Aug 11 2026 - 15:47:13 EST
The ABX80X RTC driver performs multi-step register operations such as
NVMEM transfers or register writes preceded by a configuration key
write. Add a mutex to serialize all the register writes to protect
these sequences against race conditions.
Signed-off-by: Antoni Pokusinski <apokusinski01@xxxxxxxxx>
---
drivers/rtc/rtc-abx80x.c | 45 +++++++++++++++++++++++++++++++++-------
1 file changed, 37 insertions(+), 8 deletions(-)
diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
index fdf9664ebb6f..0c8d3416fd5a 100644
--- a/drivers/rtc/rtc-abx80x.c
+++ b/drivers/rtc/rtc-abx80x.c
@@ -15,6 +15,7 @@
#include <linux/i2c.h>
#include <linux/kstrtox.h>
#include <linux/module.h>
+#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/rtc.h>
#include <linux/watchdog.h>
@@ -127,6 +128,7 @@ struct abx80x_priv {
struct rtc_device *rtc;
struct i2c_client *client;
struct watchdog_device wdog;
+ struct mutex lock;
};
static int abx80x_write_config_key(struct i2c_client *client, u8 key)
@@ -219,6 +221,7 @@ static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
unsigned char buf[8];
int err, flags;
@@ -234,6 +237,8 @@ static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
buf[ABX8XX_REG_YR] = bin2bcd(tm->tm_year - 100);
buf[ABX8XX_REG_WD] = tm->tm_wday;
+ guard(mutex)(&priv->lock);
+
err = i2c_smbus_write_i2c_block_data(client, ABX8XX_REG_HTH,
sizeof(buf), buf);
if (err < 0) {
@@ -263,6 +268,8 @@ static irqreturn_t abx80x_handle_irq(int irq, void *dev_id)
struct rtc_device *rtc = priv->rtc;
int status;
+ guard(mutex)(&priv->lock);
+
status = i2c_smbus_read_byte_data(client, ABX8XX_REG_STATUS);
if (status < 0)
return IRQ_NONE;
@@ -317,6 +324,7 @@ static int abx80x_read_alarm(struct device *dev, struct rtc_wkalrm *t)
static int abx80x_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
u8 alarm[6];
int err;
@@ -330,6 +338,8 @@ static int abx80x_set_alarm(struct device *dev, struct rtc_wkalrm *t)
alarm[4] = bin2bcd(t->time.tm_mday);
alarm[5] = bin2bcd(t->time.tm_mon + 1);
+ guard(mutex)(&priv->lock);
+
err = i2c_smbus_write_i2c_block_data(client, ABX8XX_REG_AHTH,
sizeof(alarm), alarm);
if (err < 0) {
@@ -352,6 +362,7 @@ static int abx80x_rtc_set_autocalibration(struct device *dev,
int autocalibration)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
int retval, flags = 0;
if ((autocalibration != 0) && (autocalibration != 1024) &&
@@ -360,6 +371,8 @@ static int abx80x_rtc_set_autocalibration(struct device *dev,
return -EINVAL;
}
+ guard(mutex)(&priv->lock);
+
flags = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
if (flags < 0)
return flags;
@@ -443,6 +456,7 @@ static ssize_t oscillator_store(struct device *dev,
const char *buf, size_t count)
{
struct i2c_client *client = to_i2c_client(dev->parent);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
int retval, flags, rc_mode = 0;
if (strncmp(buf, "rc", 2) == 0) {
@@ -454,6 +468,8 @@ static ssize_t oscillator_store(struct device *dev,
return -EINVAL;
}
+ guard(mutex)(&priv->lock);
+
flags = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
if (flags < 0)
return flags;
@@ -511,8 +527,11 @@ static const struct attribute_group rtc_calib_attr_group = {
static int abx80x_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
int err;
+ guard(mutex)(&priv->lock);
+
if (enabled)
err = i2c_smbus_write_byte_data(client, ABX8XX_REG_IRQ,
(ABX8XX_IRQ_IM_1_4 |
@@ -526,6 +545,7 @@ static int abx80x_alarm_irq_enable(struct device *dev, unsigned int enabled)
static int abx80x_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct abx80x_priv *priv = i2c_get_clientdata(client);
int status, tmp;
switch (cmd) {
@@ -539,16 +559,18 @@ static int abx80x_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
return put_user(tmp, (unsigned int __user *)arg);
case RTC_VL_CLR:
- status = i2c_smbus_read_byte_data(client, ABX8XX_REG_STATUS);
- if (status < 0)
- return status;
+ scoped_guard(mutex, &priv->lock) {
+ status = i2c_smbus_read_byte_data(client, ABX8XX_REG_STATUS);
+ if (status < 0)
+ return status;
- status &= ~ABX8XX_STATUS_BLF;
+ status &= ~ABX8XX_STATUS_BLF;
- tmp = i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS,
- status);
- if (tmp < 0)
- return tmp;
+ tmp = i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS,
+ status);
+ if (tmp < 0)
+ return tmp;
+ }
return 0;
@@ -617,6 +639,8 @@ static int __abx80x_wdog_set_timeout(struct watchdog_device *wdog,
struct abx80x_priv *priv = watchdog_get_drvdata(wdog);
u8 val = ABX8XX_WDT_WDS | timeout_bits(timeout);
+ guard(mutex)(&priv->lock);
+
/*
* Writing any timeout to the WDT register resets the watchdog timer.
* Writing 0 disables it.
@@ -701,6 +725,8 @@ static int abx80x_nvmem_xfer(struct abx80x_priv *priv, unsigned int offset,
len = min(lower + bytes, (size_t)ABX8XX_SRAM_WIN_SIZE) - lower;
len = min_t(u8, len, I2C_SMBUS_BLOCK_MAX);
+ guard(mutex)(&priv->lock);
+
ret = i2c_smbus_write_byte_data(priv->client, ABX8XX_REG_EXTRAM,
extram);
if (ret)
@@ -908,6 +934,9 @@ static int abx80x_probe(struct i2c_client *client)
priv->rtc->ops = &abx80x_rtc_ops;
priv->client = client;
+ err = devm_mutex_init(&client->dev, &priv->lock);
+ if (err)
+ return err;
i2c_set_clientdata(client, priv);
--
2.55.0