hwmon: scmi: Scale values to target desired HWMON units

If the SCMI firmware implementation is reporting values in a scale that
is different from the HWMON units, we need to scale up or down the value
according to how far apart they are.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
[sudeep.holla: added check of scale = 0 for early exit in scmi_hwmon_scale]
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
index a80183a..0c93fc5 100644 (file)
--- a/drivers/hwmon/scmi-hwmon.c
+++ b/drivers/hwmon/scmi-hwmon.c
@@ -18,6 +18,50 @@ struct scmi_sensors {
        const struct scmi_sensor_info **info[hwmon_max];
 };
 
+static inline u64 __pow10(u8 x)
+{
+       u64 r = 1;
+
+       while (x--)
+               r *= 10;
+
+       return r;
+}
+
+static int scmi_hwmon_scale(const struct scmi_sensor_info *sensor, u64 *value)
+{
+       s8 scale = sensor->scale;
+       u64 f;
+
+       switch (sensor->type) {
+       case TEMPERATURE_C:
+       case VOLTAGE:
+       case CURRENT:
+               scale += 3;
+               break;
+       case POWER:
+       case ENERGY:
+               scale += 6;
+               break;
+       default:
+               break;
+       }
+
+       if (scale == 0)
+               return 0;
+
+       if (abs(scale) > 19)
+               return -E2BIG;
+
+       f = __pow10(abs(scale));
+       if (scale > 0)
+               *value *= f;
+       else
+               *value = div64_u64(*value, f);
+
+       return 0;
+}
+
 static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
                           u32 attr, int channel, long *val)
 {
@@ -29,6 +73,10 @@ static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 
        sensor = *(scmi_sensors->info[type] + channel);
        ret = h->sensor_ops->reading_get(h, sensor->id, false, &value);
+       if (ret)
+               return ret;
+
+       ret = scmi_hwmon_scale(sensor, &value);
        if (!ret)
                *val = value;