ARM SCMI updates/fixes for v5.3

1. Correction to ARM document ID referred in SCMI protocol binding
 2. Fix to correct bitfield definitions for SENSOR_DESC attributes which
    otherwise will calculate sensor values on wrong scale
 3. Adds the missing rate_discrete flag setting so that discrete clocks
    are handled correctly. Without this fix it assumes continuous range
    which is incorrect
 4. Adds support to read and scale the sensor values based on the factor
    read from the firmware
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Merge tag 'scmi-updates-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/drivers

ARM SCMI updates/fixes for v5.3

1. Correction to ARM document ID referred in SCMI protocol binding
2. Fix to correct bitfield definitions for SENSOR_DESC attributes which
   otherwise will calculate sensor values on wrong scale
3. Adds the missing rate_discrete flag setting so that discrete clocks
   are handled correctly. Without this fix it assumes continuous range
   which is incorrect
4. Adds support to read and scale the sensor values based on the factor
   read from the firmware

* tag 'scmi-updates-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  hwmon: scmi: Scale values to target desired HWMON units
  firmware: arm_scmi: fetch and store sensor scale
  firmware: arm_scmi: update rate_discrete in clock_describe_rates_get
  firmware: arm_scmi: fix bitfield definitions for SENSOR_DESC attributes
  dt-bindings: arm: fix the document ID for SCMI protocol documentation

Signed-off-by: Olof Johansson <olof@lixom.net>

Documentation/devicetree/bindings/arm/arm,scmi.txt

@@ -6,7 +6,7 @@ that are provided by the hardware platform it is running on, including power
 and performance functions.
 
 This binding is intended to define the interface the firmware implementing
-the SCMI as described in ARM document number ARM DUI 0922B ("ARM System Control
+the SCMI as described in ARM document number ARM DEN 0056A ("ARM System Control
 and Management Interface Platform Design Document")[0] provide for OSPM in
 the device tree.
 

drivers/firmware/arm_scmi/clock.c

@@ -185,6 +185,8 @@ scmi_clock_describe_rates_get(const struct scmi_handle *handle, u32 clk_id,
 	if (rate_discrete)
 		clk->list.num_rates = tot_rate_cnt;
 
+	clk->rate_discrete = rate_discrete;
+
 err:
 	scmi_xfer_put(handle, t);
 	return ret;

drivers/firmware/arm_scmi/sensors.c

@@ -30,10 +30,12 @@ struct scmi_msg_resp_sensor_description {
 		__le32 id;
 		__le32 attributes_low;
 #define SUPPORTS_ASYNC_READ(x)	((x) & BIT(31))
-#define NUM_TRIP_POINTS(x)	(((x) >> 4) & 0xff)
+#define NUM_TRIP_POINTS(x)	((x) & 0xff)
 		__le32 attributes_high;
 #define SENSOR_TYPE(x)		((x) & 0xff)
-#define SENSOR_SCALE(x)		(((x) >> 11) & 0x3f)
+#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);
 		}
 

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;
 

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];
 };