amd-pstate: Introduce a tracepoint trace_amd_pstate_cppc_req2()

Introduce a new tracepoint trace_amd_pstate_cppc_req2() to track
updates to MSR_AMD_CPPC_REQ2.

Invoke this while changing the Floor Perf.

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>

Author: gautshen

drivers/cpufreq/amd-pstate-trace.h

@@ -133,6 +133,41 @@ TRACE_EVENT(amd_pstate_epp_perf,
 		 )
 );
 
+TRACE_EVENT(amd_pstate_cppc_req2,
+
+	TP_PROTO(unsigned int cpu_id,
+		 u8 floor_perf,
+		 bool changed,
+		 int err_code
+		 ),
+
+	TP_ARGS(cpu_id,
+		floor_perf,
+		changed,
+		err_code),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, cpu_id)
+		__field(u8, floor_perf)
+		__field(bool, changed)
+		__field(int, err_code)
+		),
+
+	TP_fast_assign(
+		__entry->cpu_id = cpu_id;
+		__entry->floor_perf = floor_perf;
+		__entry->changed = changed;
+		__entry->err_code = err_code;
+		),
+
+	TP_printk("cpu%u: floor_perf=%u, changed=%u (error = %d)",
+		  __entry->cpu_id,
+		  __entry->floor_perf,
+		  __entry->changed,
+		  __entry->err_code
+		 )
+);
+
 #endif /* _AMD_PSTATE_TRACE_H */
 
 /* This part must be outside protection */

drivers/cpufreq/amd-pstate.c

@@ -333,6 +333,7 @@ static int amd_pstate_set_floor_perf(struct cpufreq_policy *policy, u8 perf)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
 	u64 value, prev;
+	bool changed;
 	int ret;
 
 	if (!cpu_feature_enabled(X86_FEATURE_CPPC_PERF_PRIO))
@@ -341,17 +342,24 @@ static int amd_pstate_set_floor_perf(struct cpufreq_policy *policy, u8 perf)
 	value = prev = READ_ONCE(cpudata->cppc_req2_cached);
 	FIELD_MODIFY(AMD_CPPC_FLOOR_PERF_MASK, &value, perf);
 
-	if (value == prev)
-		return 0;
+	changed = value != prev;
+	if (!changed) {
+		ret = 0;
+		goto out_trace;
+	}
 
 	ret = wrmsrq_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ2, value);
 	if (ret) {
+		changed = false;
 		pr_err("failed to set CPPC REQ2 value. Error (%d)\n", ret);
-		return ret;
+		goto out_trace;
 	}
 
 	WRITE_ONCE(cpudata->cppc_req2_cached, value);
 
+out_trace:
+	if (trace_amd_pstate_cppc_req2_enabled())
+		trace_amd_pstate_cppc_req2(cpudata->cpu, perf, changed, ret);
 	return ret;
 }