[PATCH 13/15] cpufreq/amd-pstate: Check if CPPC request has changed before writing to the MSR or shared memory

[Mario Limonciello]

Move the common MSR field formatting code to msr_update_perf() from
its callers.

Ensure that the MSR write is necessary before flushing a write out.
Also drop the comparison from the passive flow tracing.

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 drivers/cpufreq/amd-pstate-trace.h |  7 +----
 drivers/cpufreq/amd-pstate.c       | 47 +++++++++++-------------------
 2 files changed, 18 insertions(+), 36 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate-trace.h b/drivers/cpufreq/amd-pstate-trace.h
index e2221a4b6901c..8d692415d9050 100644
--- a/drivers/cpufreq/amd-pstate-trace.h
+++ b/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"
 		 )
 );
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 8598f50e18b58..06464e2dd905f 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -224,15 +224,26 @@ 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, u32 epp, bool fast_switch)
 {
-	u64 value;
+	u64 value, prev;
+
+	value = prev = READ_ONCE(cpudata->cppc_req_cached);
+
+	value &= ~(AMD_PSTATE_MAX_PERF_MASK | AMD_PSTATE_MIN_PERF_MASK |
+		   AMD_PSTATE_DES_PERF_MASK | AMD_PSTATE_EPP_PERF_MASK);
+	value |= FIELD_PREP(AMD_PSTATE_MAX_PERF_MASK, max_perf);
+	value |= FIELD_PREP(AMD_PSTATE_DES_PERF_MASK, des_perf);
+	value |= FIELD_PREP(AMD_PSTATE_MIN_PERF_MASK, min_perf);
+	value |= FIELD_PREP(AMD_PSTATE_EPP_PERF_MASK, epp);
+
+	if (value == prev)
+		return 0;
 
-	value = READ_ONCE(cpudata->cppc_req_cached);
 	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,
-					READ_ONCE(cpudata->cppc_req_cached));
+		int ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
+
 		if (ret)
 			return ret;
 	}
@@ -528,9 +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);
 
@@ -546,27 +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_PSTATE_MAX_PERF_MASK | AMD_PSTATE_MIN_PERF_MASK |
-		   AMD_PSTATE_DES_PERF_MASK);
-	value |= FIELD_PREP(AMD_PSTATE_MAX_PERF_MASK, max_perf);
-	value |= FIELD_PREP(AMD_PSTATE_DES_PERF_MASK, des_perf);
-	value |= FIELD_PREP(AMD_PSTATE_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;
-
-	WRITE_ONCE(cpudata->cppc_req_cached, value);
-
 	amd_pstate_update_perf(cpudata, min_perf, des_perf, max_perf, 0, fast_switch);
 
-cpufreq_policy_put:
-
 	cpufreq_cpu_put(policy);
 }
 
@@ -1564,19 +1560,10 @@ 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_PSTATE_MAX_PERF_MASK | AMD_PSTATE_MIN_PERF_MASK |
-		   AMD_PSTATE_DES_PERF_MASK | AMD_PSTATE_EPP_PERF_MASK);
-	value |= FIELD_PREP(AMD_PSTATE_MAX_PERF_MASK, cpudata->max_limit_perf);
-	value |= FIELD_PREP(AMD_PSTATE_DES_PERF_MASK, 0);
-	value |= FIELD_PREP(AMD_PSTATE_MIN_PERF_MASK, cpudata->min_limit_perf);
-
 	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
 		epp = 0;
 	else
-- 
2.43.0