firmware: arm_scmi: Add power_scale_mw_get() interface

Add a new interface to the existing perf_ops and export the information
about the power values scale.

This would be used by the cpufreq driver and Energy Model framework to
set the performance domains scale: milli-Watts or abstract scale.
Suggested-by: NMorten Rasmussen <morten.rasmussen@arm.com>
Reviewed-by: NCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: NLukasz Luba <lukasz.luba@arm.com>
Acked-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

drivers/firmware/arm_scmi/perf.c

@@ -750,6 +750,13 @@ static bool scmi_fast_switch_possible(const struct scmi_handle *handle,
 	return dom->fc_info && dom->fc_info->level_set_addr;
 }
 
+static bool scmi_power_scale_mw_get(const struct scmi_handle *handle)
+{
+	struct scmi_perf_info *pi = handle->perf_priv;
+
+	return pi->power_scale_mw;
+}
+
 static const struct scmi_perf_ops perf_ops = {
 	.limits_set = scmi_perf_limits_set,
 	.limits_get = scmi_perf_limits_get,
@@ -762,6 +769,7 @@ static const struct scmi_perf_ops perf_ops = {
 	.freq_get = scmi_dvfs_freq_get,
 	.est_power_get = scmi_dvfs_est_power_get,
 	.fast_switch_possible = scmi_fast_switch_possible,
+	.power_scale_mw_get = scmi_power_scale_mw_get,
 };
 
 static int scmi_perf_set_notify_enabled(const struct scmi_handle *handle,

include/linux/scmi_protocol.h

@@ -121,6 +121,7 @@ struct scmi_perf_ops {
 			     unsigned long *rate, unsigned long *power);
 	bool (*fast_switch_possible)(const struct scmi_handle *handle,
 				     struct device *dev);
+	bool (*power_scale_mw_get)(const struct scmi_handle *handle);
 };
 
 /**