cpufreq/amd-pstate: Fix setting of CPPC.min_perf in active mode for performance governor

In the "active" mode of the amd-pstate driver with performance
governor, the CPPC.min_perf is expected to be the nominal_perf.

However after commit a9b9b4c ("cpufreq/amd-pstate: Drop min and
max cached frequencies"), this is not the case when the governor is
switched from performance to powersave and back to performance, and
the CPPC.min_perf will be equal to the scaling_min_freq that was set
for the powersave governor.

This is because prior to commit a9b9b4c ("cpufreq/amd-pstate:
Drop min and max cached frequencies"), amd_pstate_epp_update_limit()
would unconditionally call amd_pstate_update_min_max_limit() and the
latter function would enforce the CPPC.min_perf constraint when the
governor is performance.

However, after the aforementioned commit,
amd_pstate_update_min_max_limit() is called by
amd_pstate_epp_update_limit() only when either the
scaling_{min/max}_freq is different from the cached value of
cpudata->{min/max}_limit_freq, which wouldn't have changed on a
governor transition from powersave to performance, thus missing out on
enforcing the CPPC.min_perf constraint for the performance governor.

Fix this by invoking amd_pstate_epp_udpate_limit() not only when the
{min/max} limits have changed from the cached values, but also when
the policy itself has changed.

Fixes: a9b9b4c ("cpufreq/amd-pstate: Drop min and max cached frequencies")
Signed-off-by: Gautham R. Shenoy <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mario Limonciello (AMD) <[email protected]>

Author: gautshen

drivers/cpufreq/amd-pstate.c

@@ -1554,13 +1554,15 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
 	pr_debug("CPU %d exiting\n", policy->cpu);
 }
 
-static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
+static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy, bool policy_change)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
 	union perf_cached perf;
 	u8 epp;
 
-	if (policy->min != cpudata->min_limit_freq || policy->max != cpudata->max_limit_freq)
+	if (policy_change ||
+	    policy->min != cpudata->min_limit_freq ||
+	    policy->max != cpudata->max_limit_freq)
 		amd_pstate_update_min_max_limit(policy);
 
 	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
@@ -1584,7 +1586,7 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
 
 	cpudata->policy = policy->policy;
 
-	ret = amd_pstate_epp_update_limit(policy);
+	ret = amd_pstate_epp_update_limit(policy, true);
 	if (ret)
 		return ret;
 
@@ -1658,7 +1660,7 @@ static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
 		int ret;
 
 		/* enable amd pstate from suspend state*/
-		ret = amd_pstate_epp_update_limit(policy);
+		ret = amd_pstate_epp_update_limit(policy, false);
 		if (ret)
 			return ret;