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Mon, 10 Aug 2026 12:40:05 -0700 (PDT) From: Antoni Pokusinski To: alexandre.belloni@bootlin.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org Cc: linux-rtc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Antoni Pokusinski Subject: [PATCH v4 3/9] rtc: abx80x: add mutex protection for register writes Date: Mon, 10 Aug 2026 21:38:20 +0200 Message-ID: <20260810193826.210683-4-apokusinski01@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260810193826.210683-1-apokusinski01@gmail.com> References: <20260810193826.210683-1-apokusinski01@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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 #include #include +#include #include #include #include @@ -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