Re: [PATCH v3 2/2] hwmon: scmi: Scale values to target desired HWMON units

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On 5/7/19 4:09 PM, Florian Fainelli wrote:
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@xxxxxxxxx>
---
  drivers/hwmon/scmi-hwmon.c | 43 +++++++++++++++++++++++++++++++++++++-
  1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
index a80183a488c5..7820854e5954 100644
--- a/drivers/hwmon/scmi-hwmon.c
+++ b/drivers/hwmon/scmi-hwmon.c
@@ -18,6 +18,47 @@ struct scmi_sensors {
  	const struct scmi_sensor_info **info[hwmon_max];
  };
+static inline u64 __pow10(u8 x)
+{
+	u64 r = 1;
+
+	if (unlikely(x > 18))
+		return r;
+

Strictly speaking that would be 19 (10^19=0x8AC7230489E80000),
and I am not sure if returning 1 in that case is such a good idea.
If you really want to handle over/underflow situations, it should
be in the calling code.

Thanks,
Guenter

+	while (x--)
+		r *= 10;
+
+	return r;
+}
+
+static u64 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;
+	}
+
+	f = __pow10(abs(scale));
+	if (scale > 0)
+		value *= f;
+	else
+		value = div64_u64(value, f);
+
+        return value;
+}
+
  static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
  			   u32 attr, int channel, long *val)
  {
@@ -30,7 +71,7 @@ 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;
  }





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