[PATCH v2 6/9] amd-pstate: Add sysfs support for floor_freq and floor_count

["Gautham R. Shenoy" <gautham.shenoy@amd.com>]

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.

Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
---
 drivers/cpufreq/amd-pstate.c | 50 ++++++++++++++++++++++++++++++++++++
 drivers/cpufreq/amd-pstate.h |  2 ++
 2 files changed, 52 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 3122ad5af6f47..54b650f3b4e78 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -383,6 +383,8 @@ static int amd_pstate_init_floor_perf(struct cpufreq_policy *policy)
 			return ret;
 	}
 
+	cpudata->floor_freq = perf_to_freq(cpudata->perf, cpudata->nominal_freq,
+					   floor_perf);
 	return 0;
 }
 
@@ -1284,6 +1286,44 @@ 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;
+
+	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);
 
@@ -1292,6 +1332,8 @@ 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;
@@ -1316,6 +1358,12 @@ 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},
@@ -1324,6 +1372,8 @@ 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)
diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
index 0c587ca200199..ab4caea39f0e8 100644
--- a/drivers/cpufreq/amd-pstate.h
+++ b/drivers/cpufreq/amd-pstate.h
@@ -72,6 +72,7 @@ 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)
@@ -100,6 +101,7 @@ 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;
-- 
2.34.1