cpufreq: scmi: Set transition_delay_us

Make use of the newly added callbacks:
- rate_limit_get()
- fast_switch_rate_limit()
to populate policies's `transition_delay_us`, defined as the
'Preferred average time interval between consecutive
invocations of the driver to set the frequency for this policy.'
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/scmi-cpufreq.c

@@ -144,6 +144,29 @@ scmi_get_cpu_power(struct device *cpu_dev, unsigned long *power,
 	return 0;
 }
 
+static int
+scmi_get_rate_limit(u32 domain, bool has_fast_switch)
+{
+	int ret, rate_limit;
+
+	if (has_fast_switch) {
+		/*
+		 * Fast channels are used whenever available,
+		 * so use their rate_limit value if populated.
+		 */
+		ret = perf_ops->fast_switch_rate_limit(ph, domain,
+						       &rate_limit);
+		if (!ret && rate_limit)
+			return rate_limit;
+	}
+
+	ret = perf_ops->rate_limit_get(ph, domain, &rate_limit);
+	if (ret)
+		return 0;
+
+	return rate_limit;
+}
+
 static int scmi_cpufreq_init(struct cpufreq_policy *policy)
 {
 	int ret, nr_opp, domain;
@@ -250,6 +273,9 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
 	policy->fast_switch_possible =
 		perf_ops->fast_switch_possible(ph, domain);
 
+	policy->transition_delay_us =
+		scmi_get_rate_limit(domain, policy->fast_switch_possible);
+
 	return 0;
 
 out_free_opp: