[PATCH] cpufreq: Use a non-boost reference frequency for pressure calculation

[PATCH] cpufreq: Use a non-boost reference frequency for pressure calculation

[Jianyong Wu]

Commit d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall
back to cpuinfo.max_freq") introduced cpuinfo.max_freq as the reference
frequency for cpufreq pressure when arch_scale_freq_ref() returns zero.

However, cpuinfo.max_freq may include boost frequencies and therefore
does not necessarily represent the maximum sustainable frequency. On
some systems using acpi-cpufreq, cpuinfo.max_freq includes boost while
the frequency table only contains non-boost frequencies. Consequently,
cpufreq pressure remains nonzero even without an additional frequency
limit.

Furthermore, drivers may update cpuinfo.max_freq when boost is enabled
or disabled. With a fixed policy limit below the maximum non-boost
frequency, this changes the pressure reference and hence the reported
pressure, although the non-boost frequency limit remains unchanged.

Add max_sustainable_freq to struct cpufreq_cpuinfo to provide a reference
frequency excluding boost. Populate it from the nominal frequency in
amd-pstate and cppc_cpufreq, the maximum non-turbo frequency in
intel_pstate, and the highest frequency-table entry in acpi-cpufreq.

Use this value when arch_scale_freq_ref() returns zero. Preserve the
existing cpuinfo.max_freq fallback for drivers that leave the new field
at zero.

Tested with acpi-cpufreq, intel_pstate, and amd-pstate in active and
passive modes. With no additional frequency limit, pressure is zero.
With a fixed limit below the non-boost reference frequency, pressure
remains unchanged across boost transitions.

Fixes: d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall back to cpuinfo.max_freq")
Signed-off-by: Jianyong Wu <wujianyong@hygon.cn>
---
The earlier fix was incorrect and has been abandoned. This patch takes
a different approach.

Previous discussion: https://lore.kernel.org/all/SI2PR04MB4931A8BA0EF213B0238BD9E4E3BD2@SI2PR04MB4931.apcprd04.prod.outlook.com/

 drivers/cpufreq/acpi-cpufreq.c | 3 +++
 drivers/cpufreq/amd-pstate.c   | 2 ++
 drivers/cpufreq/cppc_cpufreq.c | 3 ++-
 drivers/cpufreq/cpufreq.c      | 4 +++-
 drivers/cpufreq/intel_pstate.c | 2 ++
 include/linux/cpufreq.h        | 2 ++
 6 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 21639d9ac753..e7b22456ebb8 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -856,6 +856,9 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	}
 	freq_table[valid_states].frequency = CPUFREQ_TABLE_END;
 
+	/* Init max sustainable cpu frequency */
+	policy->cpuinfo.max_sustainable_freq = freq_table[0].frequency;
+
 	max_boost_ratio = get_max_boost_ratio(cpu, &nominal_freq);
 	if (max_boost_ratio) {
 		unsigned int freq = nominal_freq;
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 3a6b4b224a66..6fc28bb1499b 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1085,6 +1085,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
 						perf.lowest_perf);
 	policy->cpuinfo.max_freq = cpudata->max_freq;
 
+	policy->cpuinfo.max_sustainable_freq = cpudata->nominal_freq;
 	policy->driver_data = cpudata;
 	ret = amd_pstate_cppc_enable(policy);
 	if (ret)
@@ -1912,6 +1913,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
 	policy->cpuinfo.min_freq = perf_to_freq(perf, cpudata->nominal_freq,
 						perf.lowest_perf);
 	policy->cpuinfo.max_freq = cpudata->max_freq;
+	policy->cpuinfo.max_sustainable_freq = cpudata->nominal_freq;
 	policy->driver_data = cpudata;
 
 	ret = amd_pstate_cppc_enable(policy);
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 6fe0e972952a..f803fcdca483 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -682,7 +682,8 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->cpuinfo.min_freq = cppc_perf_to_khz(caps, caps->lowest_perf);
 	policy->cpuinfo.max_freq = cppc_perf_to_khz(caps, policy->boost_enabled ?
 						    caps->highest_perf : caps->nominal_perf);
-
+	policy->cpuinfo.max_sustainable_freq =
+		cppc_perf_to_khz(caps, caps->nominal_perf);
 	policy->transition_delay_us = cppc_cpufreq_get_transition_delay_us(cpu);
 	policy->shared_type = cpu_data->shared_type;
 
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index b898b6544069..c1d54a22265d 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2587,7 +2587,9 @@ static void cpufreq_update_pressure(struct cpufreq_policy *policy)
 	cpu = cpumask_first(policy->related_cpus);
 	max_freq = arch_scale_freq_ref(cpu);
 	if (!max_freq)
-		max_freq = policy->cpuinfo.max_freq;
+		max_freq = policy->cpuinfo.max_sustainable_freq ?
+				 policy->cpuinfo.max_sustainable_freq :
+				 policy->cpuinfo.max_freq;
 
 	capped_freq = policy->max;
 
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 6e984c114d96..daef7e99fead 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1474,6 +1474,7 @@ static void __intel_pstate_update_max_freq(struct cpufreq_policy *policy,
 
 	policy->cpuinfo.max_freq = READ_ONCE(global.no_turbo) ?
 			cpudata->pstate.max_freq : cpudata->pstate.turbo_freq;
+	policy->cpuinfo.max_sustainable_freq = cpudata->pstate.max_freq;
 
 	refresh_frequency_limits(policy);
 }
@@ -3052,6 +3053,7 @@ static int __intel_pstate_cpu_init(struct cpufreq_policy *policy)
 	policy->cpuinfo.min_freq = cpu->pstate.min_freq;
 	policy->cpuinfo.max_freq = READ_ONCE(global.no_turbo) ?
 			cpu->pstate.max_freq : cpu->pstate.turbo_freq;
+	policy->cpuinfo.max_sustainable_freq = cpu->pstate.max_freq;
 
 	intel_pstate_init_acpi_perf_limits(policy);
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index ae9d1ce4f49c..aa3f60a167be 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -45,6 +45,8 @@ enum cpufreq_table_sorting {
 struct cpufreq_cpuinfo {
 	unsigned int		max_freq;
 	unsigned int		min_freq;
+	/* Maximum sustainable frequency excluding boost, or 0 if unknown. */
+	unsigned int		max_sustainable_freq;
 
 	/* in 10^(-9) s = nanoseconds */
 	unsigned int		transition_latency;
-- 
2.34.1

Re: [PATCH] cpufreq: Use a non-boost reference frequency for pressure calculation

[Hongyan Xia]

On 9/15/2026 2:57 PM, Jianyong Wu wrote:
> Commit d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall
> back to cpuinfo.max_freq") introduced cpuinfo.max_freq as the reference
> frequency for cpufreq pressure when arch_scale_freq_ref() returns zero.
> 
> However, cpuinfo.max_freq may include boost frequencies and therefore
> does not necessarily represent the maximum sustainable frequency. On
> some systems using acpi-cpufreq, cpuinfo.max_freq includes boost while
> the frequency table only contains non-boost frequencies. Consequently,
> cpufreq pressure remains nonzero even without an additional frequency
> limit.
> 
> Furthermore, drivers may update cpuinfo.max_freq when boost is enabled
> or disabled. With a fixed policy limit below the maximum non-boost
> frequency, this changes the pressure reference and hence the reported
> pressure, although the non-boost frequency limit remains unchanged.
> 
> Add max_sustainable_freq to struct cpufreq_cpuinfo to provide a reference
> frequency excluding boost. Populate it from the nominal frequency in
> amd-pstate and cppc_cpufreq, the maximum non-turbo frequency in
> intel_pstate, and the highest frequency-table entry in acpi-cpufreq.
> 
> Use this value when arch_scale_freq_ref() returns zero. Preserve the
> existing cpuinfo.max_freq fallback for drivers that leave the new field
> at zero.

Actually, what remaining platforms are out there that can hit this path? 
 From a quick look I think no x86 or Arm platforms can hit the fallback.

> Tested with acpi-cpufreq, intel_pstate, and amd-pstate in active and
> passive modes. With no additional frequency limit, pressure is zero.
> With a fixed limit below the non-boost reference frequency, pressure
> remains unchanged across boost transitions.
> 
> Fixes: d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall back to cpuinfo.max_freq")
> Signed-off-by: Jianyong Wu <wujianyong@hygon.cn>

Looks okay to me.

Reviewed-by: Hongyan Xia <hongyan.xia@transsion.com>

> ---
> [...]

RE: [PATCH] cpufreq: Use a non-boost reference frequency for pressure calculation

[Jianyong Wu]

Hi Hongyan,

> -----Original Message-----
> From: Hongyan Xia <hongyan.xia@transsion.com>
> Sent: Tuesday, September 15, 2026 5:33 PM
> To: Jianyong Wu <wujianyong@hygon.cn>; rafael@kernel.org;
> viresh.kumar@linaro.org; kprateek.nayak@amd.com;
> vincent.guittot@linaro.org
> Cc: linux-pm@vger.kernel.org; linux-kernel@vger.kernel.org;
> ray.huang@amd.com; mario.limonciello@amd.com; perry.yuan@amd.com;
> zhanjie9@hisilicon.com; zhenglifeng1@huawei.com;
> pierre.gondois@arm.com; sumitg@nvidia.com;
> srinivas.pandruvada@linux.intel.com; lenb@kernel.org;
> zhongqiu.han@oss.qualcomm.com; jianyong.wu@outlook.com; Fengyu
> Wang <wangfengyu@hygon.cn>; Yuan Zhong <zhongyuan@hygon.cn>;
> Huangsj <huangsj@hygon.cn>
> Subject: Re: [PATCH] cpufreq: Use a non-boost reference frequency for
> pressure calculation
> 
> On 9/15/2026 2:57 PM, Jianyong Wu wrote:
> > Commit d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall
> > back to cpuinfo.max_freq") introduced cpuinfo.max_freq as the reference
> > frequency for cpufreq pressure when arch_scale_freq_ref() returns zero.
> >
> > However, cpuinfo.max_freq may include boost frequencies and therefore
> > does not necessarily represent the maximum sustainable frequency. On
> > some systems using acpi-cpufreq, cpuinfo.max_freq includes boost while
> > the frequency table only contains non-boost frequencies. Consequently,
> > cpufreq pressure remains nonzero even without an additional frequency
> > limit.
> >
> > Furthermore, drivers may update cpuinfo.max_freq when boost is
> enabled
> > or disabled. With a fixed policy limit below the maximum non-boost
> > frequency, this changes the pressure reference and hence the reported
> > pressure, although the non-boost frequency limit remains unchanged.
> >
> > Add max_sustainable_freq to struct cpufreq_cpuinfo to provide a
> reference
> > frequency excluding boost. Populate it from the nominal frequency in
> > amd-pstate and cppc_cpufreq, the maximum non-turbo frequency in
> > intel_pstate, and the highest frequency-table entry in acpi-cpufreq.
> >
> > Use this value when arch_scale_freq_ref() returns zero. Preserve the
> > existing cpuinfo.max_freq fallback for drivers that leave the new field
> > at zero.
> 
> Actually, what remaining platforms are out there that can hit this path?
>  From a quick look I think no x86 or Arm platforms can hit the fallback.
> 
Thanks for review!

There are many cpufreq drivers, and I don't have access to hardware covering
all of them. This patch therefore limits the changes to drivers relevant to
the reported issue.

Some legacy x86 drivers, such as pt-clockmod, do not populate the new field
and still use the fallback. The fallback preserves their existing behavior.

Support for the new field in other drivers can be added separately, after
verifying each driver's frequency semantics and validating the changes on
the relevant hardware.

Thanks
Jianyong
> > Tested with acpi-cpufreq, intel_pstate, and amd-pstate in active and
> > passive modes. With no additional frequency limit, pressure is zero.
> > With a fixed limit below the non-boost reference frequency, pressure
> > remains unchanged across boost transitions.
> >
> > Fixes: d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall
> back to cpuinfo.max_freq")
> > Signed-off-by: Jianyong Wu <wujianyong@hygon.cn>
> 
> Looks okay to me.
> 
> Reviewed-by: Hongyan Xia <hongyan.xia@transsion.com>
> 
> > ---
> > [...]