[PATCH v3] cpufreq/amd-pstate: Cache the max frequency in cpudata

Mario Limonciello
2026-03-26T19:39:07Z

From: "Mario Limonciello (AMD)" <superm1@kernel.org>

The value of maximum frequency is fixed and never changes. Doing
calculations every time based off of perf is unnecessary.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
v3:
* rebase on Gautham's CPPC perf priority series
* add kdoc
---
drivers/cpufreq/amd-pstate.c | 27 +++++++++------------------
drivers/cpufreq/amd-pstate.h | 2 ++
2 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index ed9fd4155a256..f207252eb5f5f 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -826,15 +826,13 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy, bool on)
{
struct amd_cpudata *cpudata = policy->driver_data;
- union perf_cached perf = READ_ONCE(cpudata->perf);
- u32 nominal_freq, max_freq;
+ u32 nominal_freq;
int ret = 0;

nominal_freq = READ_ONCE(cpudata->nominal_freq);
- max_freq = perf_to_freq(perf, cpudata->nominal_freq, perf.highest_perf);

if (on)
- policy->cpuinfo.max_freq = max_freq;
+ policy->cpuinfo.max_freq = cpudata->max_freq;
else if (policy->cpuinfo.max_freq > nominal_freq)
policy->cpuinfo.max_freq = nominal_freq;

@@ -1021,13 +1019,15 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata)

WRITE_ONCE(cpudata->nominal_freq, nominal_freq);

+ /* max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf */
max_freq = perf_to_freq(perf, nominal_freq, perf.highest_perf);
+ WRITE_ONCE(cpudata->max_freq, max_freq);
+
lowest_nonlinear_freq = perf_to_freq(perf, nominal_freq, perf.lowest_nonlinear_perf);
WRITE_ONCE(cpudata->lowest_nonlinear_freq, lowest_nonlinear_freq);

/**
* Below values need to be initialized correctly, otherwise driver will fail to load
- * max_freq is calculated according to (nominal_freq * highest_perf)/nominal_perf
* lowest_nonlinear_freq is a value between [min_freq, nominal_freq]
* Check _CPC in ACPI table objects if any values are incorrect
*/
@@ -1090,9 +1090,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.min_freq = policy->min = perf_to_freq(perf,
cpudata->nominal_freq,
perf.lowest_perf);
- policy->cpuinfo.max_freq = policy->max = perf_to_freq(perf,
- cpudata->nominal_freq,
- perf.highest_perf);
+ policy->cpuinfo.max_freq = policy->max = cpudata->max_freq;

policy->driver_data = cpudata;
ret = amd_pstate_cppc_enable(policy);
@@ -1167,14 +1165,9 @@ static void amd_pstate_cpu_exit(struct cpufreq_policy *policy)
static ssize_t show_amd_pstate_max_freq(struct cpufreq_policy *policy,
char *buf)
{
- struct amd_cpudata *cpudata;
- union perf_cached perf;
-
- cpudata = policy->driver_data;
- perf = READ_ONCE(cpudata->perf);
+ struct amd_cpudata *cpudata = policy->driver_data;

- return sysfs_emit(buf, "%u\n",
- perf_to_freq(perf, cpudata->nominal_freq, perf.highest_perf));
+ return sysfs_emit(buf, "%u\n", cpudata->max_freq);
}

static ssize_t show_amd_pstate_lowest_nonlinear_freq(struct cpufreq_policy *policy,
@@ -1702,9 +1695,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.min_freq = policy->min = perf_to_freq(perf,
cpudata->nominal_freq,
perf.lowest_perf);
- policy->cpuinfo.max_freq = policy->max = perf_to_freq(perf,
- cpudata->nominal_freq,
- perf.highest_perf);
+ policy->cpuinfo.max_freq = policy->max = cpudata->max_freq;
policy->driver_data = cpudata;

ret = amd_pstate_cppc_enable(policy);
diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
index faead0b19a8a4..32b8b26ce388f 100644
--- a/drivers/cpufreq/amd-pstate.h
+++ b/drivers/cpufreq/amd-pstate.h
@@ -73,6 +73,7 @@ struct amd_aperf_mperf {
* @min_limit_freq: Cached value of policy->min (in khz)
* @max_limit_freq: Cached value of policy->max (in khz)
* @nominal_freq: the frequency (in khz) that mapped to nominal_perf
+ * @max_freq: in ideal conditions the maximum frequency (in khz) possible frequency
* @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
@@ -103,6 +104,7 @@ struct amd_cpudata {
u32 min_limit_freq;
u32 max_limit_freq;
u32 nominal_freq;
+ u32 max_freq;
u32 lowest_nonlinear_freq;
u32 floor_freq;

--
2.53.0