[PATCH v3 0/2] Support temperature trips by HWMON core and LM90 driver

[PATCH v3 0/2] Support temperature trips by HWMON core and LM90 driver

[Dmitry Osipenko]

Hi,

It's typical for embedded devices to use LM90-compatible sensor for
monitoring of CPU core and skin temperatures. The sensor is often
used by thermal zone that performs passive cooling and emergency
shutdown on overheat, hence it's more optimal to use interrupt for
a faster notification about temperature changes. Thermal framework
provides set_trips() callback for programming of temperature trips,
let's support it by HWMON.

Changelog:

v3: - Improved patch that fixes integer overflows by fixing the hysteresis
      underflow and improving the commit message, telling that min/max/crit
      fixes are only related to the LM99 sensor. Thanks to Guenter Roeck
      for the suggestion.

v2: - Reworked set_trips() by making it generic. Now callback invokes
      the min/max temperature write method directly, instead of using
      additional new hwmon callback. This was suggested by Guenter Roeck.

    - Added new patch that fixes integer overflows in the LM90 driver.
      The fixes are necessary for supporting set_trips().

Dmitry Osipenko (2):
  hwmon: (lm90) Prevent integer underflows of temperature calculations
  hwmon: Support set_trips() of thermal device ops

 drivers/hwmon/hwmon.c | 32 ++++++++++++++++++++++++++++++++
 drivers/hwmon/lm90.c  |  9 +++++++++
 2 files changed, 41 insertions(+)

-- 
2.30.2

[PATCH v3 1/2] hwmon: (lm90) Prevent integer underflows of temperature calculations

[Dmitry Osipenko]

The min/max/crit and all other temperature values that are passed to
the driver are unlimited and value that is close to INT_MIN results in
integer underflow of the temperature calculations made by the driver
for LM99 sensor. Temperature hysteresis is among those values that need
to be limited, but limiting of hysteresis is independent from the sensor
version. Add the missing limits.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/hwmon/lm90.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index b53f17511b05..ee6b8190f08e 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -1028,6 +1028,9 @@ static int lm90_set_temp11(struct lm90_data *data, int index, long val)
 	struct reg *regp = &reg[index];
 	int err;
 
+	/* prevent integer underflow */
+	val = max(val, -128000l);
+
 	/* +16 degrees offset for temp2 for the LM99 */
 	if (data->kind == lm99 && index <= 2)
 		val -= 16000;
@@ -1088,6 +1091,9 @@ static int lm90_set_temp8(struct lm90_data *data, int index, long val)
 	struct i2c_client *client = data->client;
 	int err;
 
+	/* prevent integer underflow */
+	val = max(val, -128000l);
+
 	/* +16 degrees offset for temp2 for the LM99 */
 	if (data->kind == lm99 && index == 3)
 		val -= 16000;
@@ -1130,6 +1136,9 @@ static int lm90_set_temphyst(struct lm90_data *data, long val)
 	int temp;
 	int err;
 
+	/* prevent integer underflow */
+	val = max(val, -128000l);
+
 	if (data->kind == adt7461 || data->kind == tmp451)
 		temp = temp_from_u8_adt7461(data, data->temp8[LOCAL_CRIT]);
 	else if (data->kind == max6646)
-- 
2.30.2

[PATCH v3 2/2] hwmon: Support set_trips() of thermal device ops

[Dmitry Osipenko]

Support set_trips() callback of thermal device ops. This allows HWMON
device to operatively notify thermal core about temperature changes, which
is very handy to have in a case where HWMON sensor is used by CPU thermal
zone that performs passive cooling and emergency shutdown on overheat.
Thermal core will be able to react faster to temperature changes.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/hwmon/hwmon.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index fd47ab4e6892..e74dc81e650d 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -153,8 +153,40 @@ static int hwmon_thermal_get_temp(void *data, int *temp)
 	return 0;
 }
 
+static int hwmon_thermal_set_trips(void *data, int low, int high)
+{
+	struct hwmon_thermal_data *tdata = data;
+	struct hwmon_device *hwdev = to_hwmon_device(tdata->dev);
+	const struct hwmon_chip_info *chip = hwdev->chip;
+	const struct hwmon_channel_info **info = chip->info;
+	unsigned int i;
+
+	if (!chip->ops->write)
+		return 0;
+
+	for (i = 1; info[i] && info[i]->type != hwmon_temp; i++)
+		continue;
+
+	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MIN) {
+		int err = chip->ops->write(tdata->dev, hwmon_temp,
+					   hwmon_temp_min, tdata->index, low);
+		if (err < 0 && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MAX) {
+		int err = chip->ops->write(tdata->dev, hwmon_temp,
+					   hwmon_temp_max, tdata->index, high);
+		if (err < 0 && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	return 0;
+}
+
 static const struct thermal_zone_of_device_ops hwmon_thermal_ops = {
 	.get_temp = hwmon_thermal_get_temp,
+	.set_trips = hwmon_thermal_set_trips,
 };
 
 static void hwmon_thermal_remove_sensor(void *data)
-- 
2.30.2

Re: [PATCH v3 2/2] hwmon: Support set_trips() of thermal device ops

[Guenter Roeck]

On Mon, Jun 21, 2021 at 09:40:58PM +0300, Dmitry Osipenko wrote:
> Support set_trips() callback of thermal device ops. This allows HWMON
> device to operatively notify thermal core about temperature changes, which
> is very handy to have in a case where HWMON sensor is used by CPU thermal
> zone that performs passive cooling and emergency shutdown on overheat.
> Thermal core will be able to react faster to temperature changes.
> 

I think that warrants an explanation why it doesn't matter if the
code doesn't really set any trip points.

> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/hwmon/hwmon.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index fd47ab4e6892..e74dc81e650d 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -153,8 +153,40 @@ static int hwmon_thermal_get_temp(void *data, int *temp)
>  	return 0;
>  }
>  
> +static int hwmon_thermal_set_trips(void *data, int low, int high)
> +{
> +	struct hwmon_thermal_data *tdata = data;
> +	struct hwmon_device *hwdev = to_hwmon_device(tdata->dev);
> +	const struct hwmon_chip_info *chip = hwdev->chip;
> +	const struct hwmon_channel_info **info = chip->info;
> +	unsigned int i;
> +
> +	if (!chip->ops->write)
> +		return 0;
> +
> +	for (i = 1; info[i] && info[i]->type != hwmon_temp; i++)
> +		continue;

Why start with index 1 ? While index 0 is commonly used for chip data,
that is not mandatory.

> +
> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MIN) {
> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
> +					   hwmon_temp_min, tdata->index, low);

checkpatch will complain here because it expects an empty line after a
declaration. Since err is used in multiple conditionals, I would suggest
to declare it once in the function header.

> +		if (err < 0 && err != -EOPNOTSUPP)

"< 0" is unnecessary.

> +			return err;
> +	}
> +
> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MAX) {
> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
> +					   hwmon_temp_max, tdata->index, high);
> +		if (err < 0 && err != -EOPNOTSUPP)

"< 0" is unnecessary.

> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct thermal_zone_of_device_ops hwmon_thermal_ops = {
>  	.get_temp = hwmon_thermal_get_temp,
> +	.set_trips = hwmon_thermal_set_trips,
>  };
>  
>  static void hwmon_thermal_remove_sensor(void *data)

Re: [PATCH v3 2/2] hwmon: Support set_trips() of thermal device ops

[Dmitry Osipenko]

21.06.2021 23:30, Guenter Roeck пишет:
> On Mon, Jun 21, 2021 at 09:40:58PM +0300, Dmitry Osipenko wrote:
>> Support set_trips() callback of thermal device ops. This allows HWMON
>> device to operatively notify thermal core about temperature changes, which
>> is very handy to have in a case where HWMON sensor is used by CPU thermal
>> zone that performs passive cooling and emergency shutdown on overheat.
>> Thermal core will be able to react faster to temperature changes.
>>
> 
> I think that warrants an explanation why it doesn't matter if the
> code doesn't really set any trip points.

I'll extend the commit message.

>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  drivers/hwmon/hwmon.c | 32 ++++++++++++++++++++++++++++++++
>>  1 file changed, 32 insertions(+)
>>
>> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
>> index fd47ab4e6892..e74dc81e650d 100644
>> --- a/drivers/hwmon/hwmon.c
>> +++ b/drivers/hwmon/hwmon.c
>> @@ -153,8 +153,40 @@ static int hwmon_thermal_get_temp(void *data, int *temp)
>>  	return 0;
>>  }
>>  
>> +static int hwmon_thermal_set_trips(void *data, int low, int high)
>> +{
>> +	struct hwmon_thermal_data *tdata = data;
>> +	struct hwmon_device *hwdev = to_hwmon_device(tdata->dev);
>> +	const struct hwmon_chip_info *chip = hwdev->chip;
>> +	const struct hwmon_channel_info **info = chip->info;
>> +	unsigned int i;
>> +
>> +	if (!chip->ops->write)
>> +		return 0;
>> +
>> +	for (i = 1; info[i] && info[i]->type != hwmon_temp; i++)
>> +		continue;
> 
> Why start with index 1 ? While index 0 is commonly used for chip data,
> that is not mandatory.

This is borrowed from hwmon_thermal_register_sensors().

>> +
>> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MIN) {
>> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
>> +					   hwmon_temp_min, tdata->index, low);
> 
> checkpatch will complain here because it expects an empty line after a
> declaration. Since err is used in multiple conditionals, I would suggest
> to declare it once in the function header.

Okay, although checkpatch is happy.

./scripts/checkpatch.pl --strict v3*
---------------------------------------------------------------
v3-0001-hwmon-lm90-Prevent-integer-underflows-of-temperat.patch
---------------------------------------------------------------
total: 0 errors, 0 warnings, 0 checks, 27 lines checked

v3-0001-hwmon-lm90-Prevent-integer-underflows-of-temperat.patch has no
obvious style problems and is ready for submission.
-----------------------------------------------------------
v3-0002-hwmon-Support-set_trips-of-thermal-device-ops.patch
-----------------------------------------------------------
total: 0 errors, 0 warnings, 0 checks, 40 lines checked

>> +		if (err < 0 && err != -EOPNOTSUPP)
> 
> "< 0" is unnecessary.
> 
>> +			return err;
>> +	}
>> +
>> +	if (info[i] && info[i]->config[tdata->index] & HWMON_T_MAX) {
>> +		int err = chip->ops->write(tdata->dev, hwmon_temp,
>> +					   hwmon_temp_max, tdata->index, high);
>> +		if (err < 0 && err != -EOPNOTSUPP)
> 
> "< 0" is unnecessary.

I'll remove it in v4.