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

[Gautham R. Shenoy]

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@xxxxxxx>
---
 drivers/cpufreq/amd-pstate.c | 52 ++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index fdc1c102a873c..a0bc80a7d3f15 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1295,6 +1295,48 @@ 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);
+
+	return ret ?: count;
+}
+
+static ssize_t show_amd_pstate_floor_freq(struct cpufreq_policy *policy, char *buf)
+{
+	struct amd_cpudata *cpudata = policy->driver_data;
+	union perf_cached perf = READ_ONCE(cpudata->perf);
+	u64 cppc_req2 = READ_ONCE(cpudata->cppc_req2_cached);
+	unsigned int freq;
+	u8 floor_perf;
+
+	floor_perf = FIELD_GET(AMD_CPPC_FLOOR_PERF_MASK, cppc_req2);
+	freq = perf_to_freq(perf, cpudata->nominal_freq, floor_perf);
+
+	return sysfs_emit(buf, "%u\n", 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);
 
@@ -1303,6 +1345,8 @@ 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;
@@ -1327,6 +1371,12 @@ 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},
@@ -1335,6 +1385,8 @@ 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)
-- 
2.34.1