firmware: arm_scmi: fetch and store sensor scale

In preparation for dealing with scales within the SCMI HWMON driver,
fetch and store the sensor unit scale into the scmi_sensor_info
structure. In order to simplify computations for upper layer, take care
of sign extending the scale to a full 8-bit signed value.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
[sudeep.holla: update bitfield values as per specification]
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/sensors.c

@@ -34,6 +34,8 @@ struct scmi_msg_resp_sensor_description {
 		__le32 attributes_high;
 #define SENSOR_TYPE(x)		((x) & 0xff)
 #define SENSOR_SCALE(x)		(((x) >> 11) & 0x1f)
+#define SENSOR_SCALE_SIGN	BIT(4)
+#define SENSOR_SCALE_EXTEND	GENMASK(7, 5)
 #define SENSOR_UPDATE_SCALE(x)	(((x) >> 22) & 0x1f)
 #define SENSOR_UPDATE_BASE(x)	(((x) >> 27) & 0x1f)
 		    u8 name[SCMI_MAX_STR_SIZE];
@@ -140,6 +142,10 @@ static int scmi_sensor_description_get(const struct scmi_handle *handle,
 			s = &si->sensors[desc_index + cnt];
 			s->id = le32_to_cpu(buf->desc[cnt].id);
 			s->type = SENSOR_TYPE(attrh);
+			s->scale = SENSOR_SCALE(attrh);
+			/* Sign extend to a full s8 */
+			if (s->scale & SENSOR_SCALE_SIGN)
+				s->scale |= SENSOR_SCALE_EXTEND;
 			strlcpy(s->name, buf->desc[cnt].name, SCMI_MAX_STR_SIZE);
 		}
 

include/linux/scmi_protocol.h

@@ -144,6 +144,7 @@ struct scmi_power_ops {
 struct scmi_sensor_info {
 	u32 id;
 	u8 type;
+	s8 scale;
 	char name[SCMI_MAX_STR_SIZE];
 };