amd-pstate: Add sysfs support for floor_freq and floor_count

When Floor Performance feature is supported by the platform, expose
two sysfs files:

   * amd_pstate_floor_freq to allow userspace to request the floor
     frequency for each CPU.

   * amd_pstate_floor_count which advertises the number of distinct
     levels of floor frequencies supported on this platform.

Reset the floor_perf to bios_floor_perf in the suspend, offline, and
exit paths, and restore the value to the cached user-request
floor_freq on the resume and online paths mirroring how bios_min_perf
is handled for MSR_AMD_CPPC_REQ.

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
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.c

@@ -383,8 +383,10 @@ static int amd_pstate_init_floor_perf(struct cpufreq_policy *policy)
 			return ret;
 	}
 
-	cpudata->bios_floor_perf = floor_perf;
 
+	cpudata->bios_floor_perf = floor_perf;
+	cpudata->floor_freq = perf_to_freq(cpudata->perf, cpudata->nominal_freq,
+					   floor_perf);
 	return 0;
 }
 
@@ -1288,6 +1290,46 @@ static ssize_t show_energy_performance_preference(
 	return sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);
 }
 
+static ssize_t store_amd_pstate_floor_freq(struct cpufreq_policy *policy,
+					   const char *buf, size_t count)
+{
+	struct amd_cpudata *cpudata = policy->driver_data;
+	union perf_cached perf = READ_ONCE(cpudata->perf);
+	unsigned int freq;
+	u8 floor_perf;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &freq);
+	if (ret)
+		return ret;
+
+	if (freq < policy->cpuinfo.min_freq || freq > policy->max)
+		return -EINVAL;
+
+	floor_perf = freq_to_perf(perf, cpudata->nominal_freq, freq);
+	ret = amd_pstate_set_floor_perf(policy, floor_perf);
+
+	if (!ret)
+		cpudata->floor_freq = freq;
+
+	return ret ?: count;
+}
+
+static ssize_t show_amd_pstate_floor_freq(struct cpufreq_policy *policy, char *buf)
+{
+	struct amd_cpudata *cpudata = policy->driver_data;
+
+	return sysfs_emit(buf, "%u\n", cpudata->floor_freq);
+}
+
+static ssize_t show_amd_pstate_floor_count(struct cpufreq_policy *policy, char *buf)
+{
+	struct amd_cpudata *cpudata = policy->driver_data;
+	u8 count = cpudata->floor_perf_cnt;
+
+	return sysfs_emit(buf, "%u\n", count);
+}
+
 cpufreq_freq_attr_ro(amd_pstate_max_freq);
 cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
 
@@ -1296,6 +1338,8 @@ cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
 cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
 cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);
+cpufreq_freq_attr_rw(amd_pstate_floor_freq);
+cpufreq_freq_attr_ro(amd_pstate_floor_count);
 
 struct freq_attr_visibility {
 	struct freq_attr *attr;
@@ -1320,6 +1364,12 @@ static bool epp_visibility(void)
 	return cppc_state == AMD_PSTATE_ACTIVE;
 }
 
+/* Determines whether amd_pstate_floor_freq related attributes should be visible */
+static bool floor_freq_visibility(void)
+{
+	return cpu_feature_enabled(X86_FEATURE_CPPC_PERF_PRIO);
+}
+
 static struct freq_attr_visibility amd_pstate_attr_visibility[] = {
 	{&amd_pstate_max_freq, always_visible},
 	{&amd_pstate_lowest_nonlinear_freq, always_visible},
@@ -1328,6 +1378,8 @@ static struct freq_attr_visibility amd_pstate_attr_visibility[] = {
 	{&amd_pstate_hw_prefcore, prefcore_visibility},
 	{&energy_performance_preference, epp_visibility},
 	{&energy_performance_available_preferences, epp_visibility},
+	{&amd_pstate_floor_freq, floor_freq_visibility},
+	{&amd_pstate_floor_count, floor_freq_visibility},
 };
 
 static struct freq_attr **get_freq_attrs(void)
@@ -1748,24 +1800,39 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
 
 static int amd_pstate_cpu_online(struct cpufreq_policy *policy)
 {
-	return amd_pstate_cppc_enable(policy);
+	struct amd_cpudata *cpudata = policy->driver_data;
+	union perf_cached perf = READ_ONCE(cpudata->perf);
+	u8 cached_floor_perf;
+	int ret;
+
+	ret = amd_pstate_cppc_enable(policy);
+	if (ret)
+		return ret;
+
+	cached_floor_perf = freq_to_perf(perf, cpudata->nominal_freq, cpudata->floor_freq);
+	return amd_pstate_set_floor_perf(policy, cached_floor_perf);
 }
 
 static int amd_pstate_cpu_offline(struct cpufreq_policy *policy)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
 	union perf_cached perf = READ_ONCE(cpudata->perf);
+	int ret;
 
 	/*
 	 * Reset CPPC_REQ MSR to the BIOS value, this will allow us to retain the BIOS specified
 	 * min_perf value across kexec reboots. If this CPU is just onlined normally after this, the
 	 * limits, epp and desired perf will get reset to the cached values in cpudata struct
 	 */
-	return amd_pstate_update_perf(policy, perf.bios_min_perf,
+	ret = amd_pstate_update_perf(policy, perf.bios_min_perf,
 				     FIELD_GET(AMD_CPPC_DES_PERF_MASK, cpudata->cppc_req_cached),
 				     FIELD_GET(AMD_CPPC_MAX_PERF_MASK, cpudata->cppc_req_cached),
 				     FIELD_GET(AMD_CPPC_EPP_PERF_MASK, cpudata->cppc_req_cached),
 				     false);
+	if (ret)
+		return ret;
+
+	return amd_pstate_set_floor_perf(policy, cpudata->bios_floor_perf);
 }
 
 static int amd_pstate_suspend(struct cpufreq_policy *policy)
@@ -1787,6 +1854,10 @@ static int amd_pstate_suspend(struct cpufreq_policy *policy)
 	if (ret)
 		return ret;
 
+	ret = amd_pstate_set_floor_perf(policy, cpudata->bios_floor_perf);
+	if (ret)
+		return ret;
+
 	/* set this flag to avoid setting core offline*/
 	cpudata->suspended = true;
 
@@ -1798,15 +1869,24 @@ static int amd_pstate_resume(struct cpufreq_policy *policy)
 	struct amd_cpudata *cpudata = policy->driver_data;
 	union perf_cached perf = READ_ONCE(cpudata->perf);
 	int cur_perf = freq_to_perf(perf, cpudata->nominal_freq, policy->cur);
+	u8 cached_floor_perf;
+	int ret;
 
 	/* Set CPPC_REQ to last sane value until the governor updates it */
-	return amd_pstate_update_perf(policy, perf.min_limit_perf, cur_perf, perf.max_limit_perf,
-				      0U, false);
+	ret = amd_pstate_update_perf(policy, perf.min_limit_perf, cur_perf, perf.max_limit_perf,
+				     0U, false);
+	if (ret)
+		return ret;
+
+	cached_floor_perf = freq_to_perf(perf, cpudata->nominal_freq, cpudata->floor_freq);
+	return amd_pstate_set_floor_perf(policy, cached_floor_perf);
 }
 
 static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
 {
 	struct amd_cpudata *cpudata = policy->driver_data;
+	union perf_cached perf = READ_ONCE(cpudata->perf);
+	u8 cached_floor_perf;
 
 	if (cpudata->suspended) {
 		int ret;
@@ -1819,7 +1899,8 @@ static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
 		cpudata->suspended = false;
 	}
 
-	return 0;
+	cached_floor_perf = freq_to_perf(perf, cpudata->nominal_freq, cpudata->floor_freq);
+	return amd_pstate_set_floor_perf(policy, cached_floor_perf);
 }
 
 static struct cpufreq_driver amd_pstate_driver = {

drivers/cpufreq/amd-pstate.h

@@ -74,6 +74,7 @@ struct amd_aperf_mperf {
  * @max_limit_freq: Cached value of policy->max (in khz)
  * @nominal_freq: the frequency (in khz) that mapped to nominal_perf
  * @lowest_nonlinear_freq: the frequency (in khz) that mapped to lowest_nonlinear_perf
+ * @floor_freq: Cached value of the user requested floor_freq
  * @cur: Difference of Aperf/Mperf/tsc count between last and current sample
  * @prev: Last Aperf/Mperf/tsc count value read from register
  * @freq: current cpu frequency value (in khz)
@@ -103,6 +104,7 @@ struct amd_cpudata {
 	u32	max_limit_freq;
 	u32	nominal_freq;
 	u32	lowest_nonlinear_freq;
+	u32	floor_freq;
 
 	struct amd_aperf_mperf cur;
 	struct amd_aperf_mperf prev;