From 2938b2978a70d4cc10777ee71c9e512ffe4e0f4b Mon Sep 17 00:00:00 2001 From: Paul Fertser Date: Fri, 24 Sep 2021 12:30:09 +0300 Subject: hwmon: (tmp421) handle I2C errors Function i2c_smbus_read_byte_data() can return a negative error number instead of the data read if I2C transaction failed for whatever reason. Lack of error checking can lead to serious issues on production hardware, e.g. errors treated as temperatures produce spurious critical temperature-crossed-threshold errors in BMC logs for OCP server hardware. The patch was tested with Mellanox OCP Mezzanine card emulating TMP421 protocol for temperature sensing which sometimes leads to I2C protocol error during early boot up stage. Fixes: 9410700b881f ("hwmon: Add driver for Texas Instruments TMP421/422/423 sensor chips") Cc: stable@vger.kernel.org Signed-off-by: Paul Fertser Link: https://lore.kernel.org/r/20210924093011.26083-1-fercerpav@gmail.com [groeck: dropped unnecessary line breaks] Signed-off-by: Guenter Roeck --- drivers/hwmon/tmp421.c | 38 ++++++++++++++++++++++++++++---------- 1 file changed, 28 insertions(+), 10 deletions(-) (limited to 'drivers/hwmon/tmp421.c') diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c index ede66ea6a730..8fd8c3a94dfe 100644 --- a/drivers/hwmon/tmp421.c +++ b/drivers/hwmon/tmp421.c @@ -119,38 +119,56 @@ static int temp_from_u16(u16 reg) return (temp * 1000 + 128) / 256; } -static struct tmp421_data *tmp421_update_device(struct device *dev) +static int tmp421_update_device(struct tmp421_data *data) { - struct tmp421_data *data = dev_get_drvdata(dev); struct i2c_client *client = data->client; + int ret = 0; int i; mutex_lock(&data->update_lock); if (time_after(jiffies, data->last_updated + (HZ / 2)) || !data->valid) { - data->config = i2c_smbus_read_byte_data(client, - TMP421_CONFIG_REG_1); + ret = i2c_smbus_read_byte_data(client, TMP421_CONFIG_REG_1); + if (ret < 0) + goto exit; + data->config = ret; for (i = 0; i < data->channels; i++) { - data->temp[i] = i2c_smbus_read_byte_data(client, - TMP421_TEMP_MSB[i]) << 8; - data->temp[i] |= i2c_smbus_read_byte_data(client, - TMP421_TEMP_LSB[i]); + ret = i2c_smbus_read_byte_data(client, TMP421_TEMP_MSB[i]); + if (ret < 0) + goto exit; + data->temp[i] = ret << 8; + + ret = i2c_smbus_read_byte_data(client, TMP421_TEMP_LSB[i]); + if (ret < 0) + goto exit; + data->temp[i] |= ret; } data->last_updated = jiffies; data->valid = 1; } +exit: mutex_unlock(&data->update_lock); - return data; + if (ret < 0) { + data->valid = 0; + return ret; + } + + return 0; } static int tmp421_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel, long *val) { - struct tmp421_data *tmp421 = tmp421_update_device(dev); + struct tmp421_data *tmp421 = dev_get_drvdata(dev); + int ret = 0; + + ret = tmp421_update_device(tmp421); + if (ret) + return ret; switch (attr) { case hwmon_temp_input: -- cgit v1.2.3 From 540effa7f283d25bcc13c0940d808002fee340b8 Mon Sep 17 00:00:00 2001 From: Paul Fertser Date: Fri, 24 Sep 2021 12:30:10 +0300 Subject: hwmon: (tmp421) report /PVLD condition as fault For both local and remote sensors all the supported ICs can report an "undervoltage lockout" condition which means the conversion wasn't properly performed due to insufficient power supply voltage and so the measurement results can't be trusted. Fixes: 9410700b881f ("hwmon: Add driver for Texas Instruments TMP421/422/423 sensor chips") Signed-off-by: Paul Fertser Link: https://lore.kernel.org/r/20210924093011.26083-2-fercerpav@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/tmp421.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'drivers/hwmon/tmp421.c') diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c index 8fd8c3a94dfe..c9ef83627bb7 100644 --- a/drivers/hwmon/tmp421.c +++ b/drivers/hwmon/tmp421.c @@ -179,10 +179,10 @@ static int tmp421_read(struct device *dev, enum hwmon_sensor_types type, return 0; case hwmon_temp_fault: /* - * The OPEN bit signals a fault. This is bit 0 of the temperature - * register (low byte). + * Any of OPEN or /PVLD bits indicate a hardware mulfunction + * and the conversion result may be incorrect */ - *val = tmp421->temp[channel] & 0x01; + *val = !!(tmp421->temp[channel] & 0x03); return 0; default: return -EOPNOTSUPP; @@ -195,9 +195,6 @@ static umode_t tmp421_is_visible(const void *data, enum hwmon_sensor_types type, { switch (attr) { case hwmon_temp_fault: - if (channel == 0) - return 0; - return 0444; case hwmon_temp_input: return 0444; default: -- cgit v1.2.3 From 724e8af85854c4d3401313b6dd7d79cf792d8990 Mon Sep 17 00:00:00 2001 From: Paul Fertser Date: Fri, 24 Sep 2021 12:30:11 +0300 Subject: hwmon: (tmp421) fix rounding for negative values Old code produces -24999 for 0b1110011100000000 input in standard format due to always rounding up rather than "away from zero". Use the common macro for division, unify and simplify the conversion code along the way. Fixes: 9410700b881f ("hwmon: Add driver for Texas Instruments TMP421/422/423 sensor chips") Signed-off-by: Paul Fertser Link: https://lore.kernel.org/r/20210924093011.26083-3-fercerpav@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/tmp421.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) (limited to 'drivers/hwmon/tmp421.c') diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c index c9ef83627bb7..b963a369c5ab 100644 --- a/drivers/hwmon/tmp421.c +++ b/drivers/hwmon/tmp421.c @@ -100,23 +100,17 @@ struct tmp421_data { s16 temp[4]; }; -static int temp_from_s16(s16 reg) +static int temp_from_raw(u16 reg, bool extended) { /* Mask out status bits */ int temp = reg & ~0xf; - return (temp * 1000 + 128) / 256; -} - -static int temp_from_u16(u16 reg) -{ - /* Mask out status bits */ - int temp = reg & ~0xf; - - /* Add offset for extended temperature range. */ - temp -= 64 * 256; + if (extended) + temp = temp - 64 * 256; + else + temp = (s16)temp; - return (temp * 1000 + 128) / 256; + return DIV_ROUND_CLOSEST(temp * 1000, 256); } static int tmp421_update_device(struct tmp421_data *data) @@ -172,10 +166,8 @@ static int tmp421_read(struct device *dev, enum hwmon_sensor_types type, switch (attr) { case hwmon_temp_input: - if (tmp421->config & TMP421_CONFIG_RANGE) - *val = temp_from_u16(tmp421->temp[channel]); - else - *val = temp_from_s16(tmp421->temp[channel]); + *val = temp_from_raw(tmp421->temp[channel], + tmp421->config & TMP421_CONFIG_RANGE); return 0; case hwmon_temp_fault: /* -- cgit v1.2.3