On Thu, Mar 02, 2017 at 01:15:00PM +0100, Carlo Caione wrote:
> From: Carlo Caione <[email protected]>
>
> The implementation details for SCPI seems to suggest that the sensor
> readings must be reported by SCP using a well defined scale
> (millidegree Celsius for temperature, millivolts for voltage,
> milliamperes for current, microwatts for power and microjoules for
> energy).
>
> This is also important for the interaction with other subsystems: for
> example both the thermal sub-system and the hwmon sysfs interface expect
> the temperature expressed in millidegree Celsius.
>
> Unfortunately since this behaviour is dependent on the firmware
> implementation there are cases where the sensor readings are reported
> using a different scale. For example in the Amlogic SoCs the
> temperature is reported in degree and not millidegree Celsius.
>
> To take into account this discrepancy and fixup the values reported by
> SCP a new DT property `scpi,sensors-scale' is introduced and used in
> this patch by the scpi-hwmon driver to convert the sensor readings to
> the expected scale.
>
> Signed-off-by: Carlo Caione <[email protected]>
> ---
> drivers/hwmon/scpi-hwmon.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/hwmon/scpi-hwmon.c b/drivers/hwmon/scpi-hwmon.c
> index 094f948f99ff..64a51e06c8df 100644
> --- a/drivers/hwmon/scpi-hwmon.c
> +++ b/drivers/hwmon/scpi-hwmon.c
> @@ -23,6 +23,7 @@
> #include <linux/thermal.h>
>
> struct sensor_data {
> + unsigned int scale;
> struct scpi_sensor_info info;
> struct device_attribute dev_attr_input;
> struct device_attribute dev_attr_label;
> @@ -44,6 +45,14 @@ struct scpi_sensors {
> const struct attribute_group *groups[2];
> };
>
> +static const unsigned int scpi_scale[] = {
> + 1000, /* Temperature (millidegrees Celsius) */
> + 1000, /* Voltage (millivolts) */
> + 1000, /* Current (milliamperes) */
> + 1000000, /* Power (microwatts) */
> + 1000000, /* Energy (microjoules) */
> +};
> +
> static int scpi_read_temp(void *dev, int *temp)
> {
> struct scpi_thermal_zone *zone = dev;
> @@ -57,6 +66,11 @@ static int scpi_read_temp(void *dev, int *temp)
> if (ret)
> return ret;
>
> + if (scpi_scale[sensor->info.class] != sensor->scale) {
> + value *= scpi_scale[sensor->info.class];
> + do_div(value, sensor->scale);
Pretty elegant, I like that solution.
> + }
> +
> *temp = value;
> return 0;
> }
> @@ -77,6 +91,11 @@ scpi_show_sensor(struct device *dev, struct
> device_attribute *attr, char *buf)
> if (ret)
> return ret;
>
> + if (scpi_scale[sensor->info.class] != sensor->scale) {
> + value *= scpi_scale[sensor->info.class];
> + do_div(value, sensor->scale);
> + }
> +
> return sprintf(buf, "%llu\n", value);
> }
>
> @@ -97,6 +116,7 @@ static struct thermal_zone_of_device_ops scpi_sensor_ops =
> {
> static int scpi_hwmon_probe(struct platform_device *pdev)
> {
> u16 nr_sensors, i;
> + u32 scale[] = { 1000, 1000, 1000, 1000000, 1000000 };
> int num_temp = 0, num_volt = 0, num_current = 0, num_power = 0;
> int num_energy = 0;
> struct scpi_ops *scpi_ops;
> @@ -131,6 +151,9 @@ static int scpi_hwmon_probe(struct platform_device *pdev)
>
> scpi_sensors->scpi_ops = scpi_ops;
>
> + of_property_read_u32_array(dev->of_node, "scpi,sensors-scale",
> + scale, ARRAY_SIZE(scale));
> +
We'll need some validation here. Otherwise a provided scale of 0 would
crash the system.
Guenter
> for (i = 0, idx = 0; i < nr_sensors; i++) {
> struct sensor_data *sensor = &scpi_sensors->data[idx];
>
> @@ -178,6 +201,8 @@ static int scpi_hwmon_probe(struct platform_device *pdev)
> continue;
> }
>
> + sensor->scale = scale[sensor->info.class];
> +
> sensor->dev_attr_input.attr.mode = S_IRUGO;
> sensor->dev_attr_input.show = scpi_show_sensor;
> sensor->dev_attr_input.attr.name = sensor->input;
> --
> 2.12.0
>
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