[PATCH 2/2] hwmon: scmi: Scale values to target desired HWMON units

[Florian Fainelli <f.fainelli@gmail.com>]

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 appart they are.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 drivers/hwmon/scmi-hwmon.c | 55 +++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
index a80183a488c5..e9913509cb88 100644
--- a/drivers/hwmon/scmi-hwmon.c
+++ b/drivers/hwmon/scmi-hwmon.c
@@ -18,6 +18,51 @@ struct scmi_sensors {
 	const struct scmi_sensor_info **info[hwmon_max];
 };
 
+static enum hwmon_sensor_types scmi_types[] = {
+	[TEMPERATURE_C] = hwmon_temp,
+	[VOLTAGE] = hwmon_in,
+	[CURRENT] = hwmon_curr,
+	[POWER] = hwmon_power,
+	[ENERGY] = hwmon_energy,
+};
+
+static u64 scmi_hwmon_scale(const struct scmi_sensor_info *sensor, u64 value)
+{
+	u64 scaled_value = value;
+	s8 desired_scale;
+	int n, p;
+
+	switch (sensor->type) {
+	case TEMPERATURE_C:
+	case VOLTAGE:
+	case CURRENT:
+		/* fall through */
+		desired_scale = -3;
+		break;
+	case POWER:
+	case ENERGY:
+		/* fall through */
+		desired_scale = -6;
+		break;
+	default:
+		return scaled_value;
+	}
+
+	n = (s8)sensor->scale - desired_scale;
+        if (n == 0)
+                return scaled_value;
+
+	for (p = 0; p < abs(n); p++) {
+		/* Need to scale up from sensor to HWMON */
+		if (n > 0)
+			scaled_value *= 10;
+		else
+			do_div(scaled_value, 10);
+	}
+
+        return scaled_value;
+}
+
 static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 			   u32 attr, int channel, long *val)
 {
@@ -30,7 +75,7 @@ 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)
-		*val = value;
+		*val = scmi_hwmon_scale(sensor, value);
 
 	return ret;
 }
@@ -91,14 +136,6 @@ static int scmi_hwmon_add_chan_info(struct hwmon_channel_info *scmi_hwmon_chan,
 	return 0;
 }
 
-static enum hwmon_sensor_types scmi_types[] = {
-	[TEMPERATURE_C] = hwmon_temp,
-	[VOLTAGE] = hwmon_in,
-	[CURRENT] = hwmon_curr,
-	[POWER] = hwmon_power,
-	[ENERGY] = hwmon_energy,
-};
-
 static u32 hwmon_attributes[] = {
 	[hwmon_chip] = HWMON_C_REGISTER_TZ,
 	[hwmon_temp] = HWMON_T_INPUT | HWMON_T_LABEL,
-- 
2.17.1