[PATCH v3 06/12] amd-pstate: Add sysfs support for floor_freq and floor_count
From: Gautham R. Shenoy
Date: Fri Mar 20 2026 - 10:56:42 EST
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.
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
---
drivers/cpufreq/amd-pstate.c | 93 +++++++++++++++++++++++++++++++++---
drivers/cpufreq/amd-pstate.h | 2 +
2 files changed, 89 insertions(+), 6 deletions(-)
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 53b8173ff183..a068c4457a8f 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/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 = {
diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
index f04561da4518..2f7a96836fcd 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)
@@ -101,6 +102,7 @@ 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