cpufreq/amd-pstate: Always write EPP value when updating perf

For MSR systems the EPP value is in the same register as perf targets
and so divding them into two separate MSR writes is wasteful.

In msr_update_perf(), update both EPP and perf values in one write to
MSR_AMD_CPPC_REQ, and cache them if successful.

To accomplish this plumb the EPP value into the update_perf call and
modify all its callers to check the return value.

As this unifies calls, ensure that the MSR write is necessary before
flushing a write out. Also drop the comparison from the passive flow
tracing.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20241209185248.16301-13-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>

Author: superm1

drivers/cpufreq/amd-pstate-trace.h

@@ -32,7 +32,6 @@ TRACE_EVENT(amd_pstate_perf,
 		 u64 aperf,
 		 u64 tsc,
 		 unsigned int cpu_id,
-		 bool changed,
 		 bool fast_switch
 		 ),
 
@@ -44,7 +43,6 @@ TRACE_EVENT(amd_pstate_perf,
 		aperf,
 		tsc,
 		cpu_id,
-		changed,
 		fast_switch
 		),
 
@@ -57,7 +55,6 @@ TRACE_EVENT(amd_pstate_perf,
 		__field(unsigned long long, aperf)
 		__field(unsigned long long, tsc)
 		__field(unsigned int, cpu_id)
-		__field(bool, changed)
 		__field(bool, fast_switch)
 		),
 
@@ -70,11 +67,10 @@ TRACE_EVENT(amd_pstate_perf,
 		__entry->aperf = aperf;
 		__entry->tsc = tsc;
 		__entry->cpu_id = cpu_id;
-		__entry->changed = changed;
 		__entry->fast_switch = fast_switch;
 		),
 
-	TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu freq=%llu mperf=%llu aperf=%llu tsc=%llu cpu_id=%u changed=%s fast_switch=%s",
+	TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu freq=%llu mperf=%llu aperf=%llu tsc=%llu cpu_id=%u fast_switch=%s",
 		  (unsigned long)__entry->min_perf,
 		  (unsigned long)__entry->target_perf,
 		  (unsigned long)__entry->capacity,
@@ -83,7 +79,6 @@ TRACE_EVENT(amd_pstate_perf,
 		  (unsigned long long)__entry->aperf,
 		  (unsigned long long)__entry->tsc,
 		  (unsigned int)__entry->cpu_id,
-		  (__entry->changed) ? "true" : "false",
 		  (__entry->fast_switch) ? "true" : "false"
 		 )
 );

drivers/cpufreq/amd-pstate.c

@@ -222,25 +222,47 @@ static s16 shmem_get_epp(struct amd_cpudata *cpudata)
 }
 
 static int msr_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
-			       u32 des_perf, u32 max_perf, bool fast_switch)
+			   u32 des_perf, u32 max_perf, u32 epp, bool fast_switch)
 {
+	u64 value, prev;
+
+	value = prev = READ_ONCE(cpudata->cppc_req_cached);
+
+	value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
+		   AMD_CPPC_DES_PERF_MASK | AMD_CPPC_EPP_PERF_MASK);
+	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
+	value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, des_perf);
+	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
+	value |= FIELD_PREP(AMD_CPPC_EPP_PERF_MASK, epp);
+
+	if (value == prev)
+		return 0;
+
 	if (fast_switch) {
-		wrmsrl(MSR_AMD_CPPC_REQ, READ_ONCE(cpudata->cppc_req_cached));
+		wrmsrl(MSR_AMD_CPPC_REQ, value);
 		return 0;
+	} else {
+		int ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
+
+		if (ret)
+			return ret;
 	}
 
-	return wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
-			     READ_ONCE(cpudata->cppc_req_cached));
+	WRITE_ONCE(cpudata->cppc_req_cached, value);
+	WRITE_ONCE(cpudata->epp_cached, epp);
+
+	return 0;
 }
 
 DEFINE_STATIC_CALL(amd_pstate_update_perf, msr_update_perf);
 
 static inline int amd_pstate_update_perf(struct amd_cpudata *cpudata,
 					  u32 min_perf, u32 des_perf,
-					  u32 max_perf, bool fast_switch)
+					  u32 max_perf, u32 epp,
+					  bool fast_switch)
 {
 	return static_call(amd_pstate_update_perf)(cpudata, min_perf, des_perf,
-						   max_perf, fast_switch);
+						   max_perf, epp, fast_switch);
 }
 
 static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
@@ -261,6 +283,7 @@ static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
 		return ret;
 	}
 
+	/* update both so that msr_update_perf() can effectively check */
 	WRITE_ONCE(cpudata->epp_cached, epp);
 	WRITE_ONCE(cpudata->cppc_req_cached, value);
 
@@ -459,12 +482,18 @@ static inline int amd_pstate_init_perf(struct amd_cpudata *cpudata)
 	return static_call(amd_pstate_init_perf)(cpudata);
 }
 
-static int shmem_update_perf(struct amd_cpudata *cpudata,
-			     u32 min_perf, u32 des_perf,
-			     u32 max_perf, bool fast_switch)
+static int shmem_update_perf(struct amd_cpudata *cpudata, u32 min_perf,
+			     u32 des_perf, u32 max_perf, u32 epp, bool fast_switch)
 {
 	struct cppc_perf_ctrls perf_ctrls;
 
+	if (cppc_state == AMD_PSTATE_ACTIVE) {
+		int ret = shmem_set_epp(cpudata, epp);
+
+		if (ret)
+			return ret;
+	}
+
 	perf_ctrls.max_perf = max_perf;
 	perf_ctrls.min_perf = min_perf;
 	perf_ctrls.desired_perf = des_perf;
@@ -510,9 +539,7 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
 {
 	unsigned long max_freq;
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpudata->cpu);
-	u64 prev = READ_ONCE(cpudata->cppc_req_cached);
 	u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
-	u64 value = prev;
 
 	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
 
@@ -528,27 +555,14 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
 	if (!cpudata->boost_supported)
 		max_perf = min_t(unsigned long, nominal_perf, max_perf);
 
-	value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
-		   AMD_CPPC_DES_PERF_MASK);
-	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
-	value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, des_perf);
-	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
-
 	if (trace_amd_pstate_perf_enabled() && amd_pstate_sample(cpudata)) {
 		trace_amd_pstate_perf(min_perf, des_perf, max_perf, cpudata->freq,
 			cpudata->cur.mperf, cpudata->cur.aperf, cpudata->cur.tsc,
-				cpudata->cpu, (value != prev), fast_switch);
+				cpudata->cpu, fast_switch);
 	}
 
-	if (value == prev)
-		goto cpufreq_policy_put;
+	amd_pstate_update_perf(cpudata, min_perf, des_perf, max_perf, 0, fast_switch);
 
-	WRITE_ONCE(cpudata->cppc_req_cached, value);
-
-	amd_pstate_update_perf(cpudata, min_perf, des_perf,
-			       max_perf, fast_switch);
-
-cpufreq_policy_put:
 	cpufreq_cpu_put(policy);
 }
 
@@ -1544,36 +1558,24 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
 static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
-	u64 value;
+	u32 epp;
 
 	amd_pstate_update_min_max_limit(policy);
 
-	value = READ_ONCE(cpudata->cppc_req_cached);
-
-	value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
-		   AMD_CPPC_DES_PERF_MASK | AMD_CPPC_EPP_PERF_MASK);
-	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, cpudata->max_limit_perf);
-	value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, 0);
-	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, cpudata->min_limit_perf);
-
 	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
-		WRITE_ONCE(cpudata->epp_cached, 0);
-	value |= FIELD_PREP(AMD_CPPC_EPP_PERF_MASK, cpudata->epp_cached);
-
-	WRITE_ONCE(cpudata->cppc_req_cached, value);
+		epp = 0;
+	else
+		epp = READ_ONCE(cpudata->epp_cached);
 
 	if (trace_amd_pstate_epp_perf_enabled()) {
-		trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf,
-					  cpudata->epp_cached,
+		trace_amd_pstate_epp_perf(cpudata->cpu, cpudata->highest_perf, epp,
 					  cpudata->min_limit_perf,
 					  cpudata->max_limit_perf,
 					  policy->boost_enabled);
 	}
 
-	amd_pstate_update_perf(cpudata, cpudata->min_limit_perf, 0U,
-			       cpudata->max_limit_perf, false);
-
-	return amd_pstate_set_epp(cpudata, READ_ONCE(cpudata->epp_cached));
+	return amd_pstate_update_perf(cpudata, cpudata->min_limit_perf, 0U,
+				      cpudata->max_limit_perf, epp, false);
 }
 
 static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
@@ -1602,7 +1604,7 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
 	return 0;
 }
 
-static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
+static int amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
 {
 	u64 max_perf;
 	int ret;
@@ -1620,17 +1622,19 @@ static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
 					  max_perf, cpudata->boost_state);
 	}
 
-	amd_pstate_update_perf(cpudata, 0, 0, max_perf, false);
-	amd_pstate_set_epp(cpudata, cpudata->epp_cached);
+	return amd_pstate_update_perf(cpudata, 0, 0, max_perf, cpudata->epp_cached, false);
 }
 
 static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
+	int ret;
 
 	pr_debug("AMD CPU Core %d going online\n", cpudata->cpu);
 
-	amd_pstate_epp_reenable(cpudata);
+	ret = amd_pstate_epp_reenable(cpudata);
+	if (ret)
+		return ret;
 	cpudata->suspended = false;
 
 	return 0;
@@ -1654,10 +1658,8 @@ static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
 					  min_perf, min_perf, policy->boost_enabled);
 	}
 
-	amd_pstate_update_perf(cpudata, min_perf, 0, min_perf, false);
-	amd_pstate_set_epp(cpudata, AMD_CPPC_EPP_BALANCE_POWERSAVE);
-
-	return 0;
+	return amd_pstate_update_perf(cpudata, min_perf, 0, min_perf,
+				      AMD_CPPC_EPP_BALANCE_POWERSAVE, false);
 }
 
 static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)