[PATCH v2] cpufreq: CPPC: Enable boost by default when supported

[PATCH v2] cpufreq: CPPC: Enable boost by default when supported

[Pengjie Zhang]

The CPPC driver leaves boost disabled by default when Highest Performance
exceeds Nominal Performance. Userspace must explicitly enable boost
before governors can use the full advertised performance range.

Enable boost by default when at least one possible CPU reports support,
while users who prefer to stay within the sustained nominal limit can
still disable it via the boost knob without determining scaling_max_freq
for each policy.

Check the performance capabilities before registering the driver so that
the cpufreq core enables boost for each policy that supports it.

Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
---
Changes in v2:
- Drop "even" and clarify the commit message (Christian).
- Link to v1: https://lore.kernel.org/all/20261015015812.867988-1-zhangpengjie2@huawei.com/

 drivers/cpufreq/cppc_cpufreq.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 80893844353c..0a4255a36f60 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -1052,6 +1052,25 @@ static struct cpufreq_driver cppc_cpufreq_driver = {
 	.name = "cppc_cpufreq",
 };
 
+static void __init cppc_cpufreq_default_boost_init(void)
+{
+	struct cppc_perf_caps caps;
+	bool enable = false;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		if (cppc_get_perf_caps(cpu, &caps))
+			continue;
+
+		if (caps.highest_perf > caps.nominal_perf) {
+			enable = true;
+			break;
+		}
+	}
+
+	cppc_cpufreq_driver.boost_enabled = enable;
+}
+
 static int __init cppc_cpufreq_init(void)
 {
 	int ret;
@@ -1061,6 +1080,7 @@ static int __init cppc_cpufreq_init(void)
 
 	cppc_freq_invariance_init();
 	populate_efficiency_class();
+	cppc_cpufreq_default_boost_init();
 
 	ret = cpufreq_register_driver(&cppc_cpufreq_driver);
 	if (ret)
-- 
2.33.0

Re: [PATCH v2] cpufreq: CPPC: Enable boost by default when supported

[Pengjie Zhang]

+cc Christian Loehle

On 10/22/2026 3:59 PM, Pengjie Zhang wrote:
> The CPPC driver leaves boost disabled by default when Highest Performance
> exceeds Nominal Performance. Userspace must explicitly enable boost
> before governors can use the full advertised performance range.
>
> Enable boost by default when at least one possible CPU reports support,
> while users who prefer to stay within the sustained nominal limit can
> still disable it via the boost knob without determining scaling_max_freq
> for each policy.
>
> Check the performance capabilities before registering the driver so that
> the cpufreq core enables boost for each policy that supports it.
>
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> ---
> Changes in v2:
> - Drop "even" and clarify the commit message (Christian).
> - Link to v1: https://lore.kernel.org/all/20261015015812.867988-1-zhangpengjie2@huawei.com/
>
>   drivers/cpufreq/cppc_cpufreq.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
>
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 80893844353c..0a4255a36f60 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -1052,6 +1052,25 @@ static struct cpufreq_driver cppc_cpufreq_driver = {
>   	.name = "cppc_cpufreq",
>   };
>   
> +static void __init cppc_cpufreq_default_boost_init(void)
> +{
> +	struct cppc_perf_caps caps;
> +	bool enable = false;
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (cppc_get_perf_caps(cpu, &caps))
> +			continue;
> +
> +		if (caps.highest_perf > caps.nominal_perf) {
> +			enable = true;
> +			break;
> +		}
> +	}
> +
> +	cppc_cpufreq_driver.boost_enabled = enable;
> +}
> +
>   static int __init cppc_cpufreq_init(void)
>   {
>   	int ret;
> @@ -1061,6 +1080,7 @@ static int __init cppc_cpufreq_init(void)
>   
>   	cppc_freq_invariance_init();
>   	populate_efficiency_class();
> +	cppc_cpufreq_default_boost_init();
>   
>   	ret = cpufreq_register_driver(&cppc_cpufreq_driver);
>   	if (ret)

Re: [PATCH v2] cpufreq: CPPC: Enable boost by default when supported

[Christian Loehle]

On 10/22/26 08:59, Pengjie Zhang wrote:
> The CPPC driver leaves boost disabled by default when Highest Performance
> exceeds Nominal Performance. Userspace must explicitly enable boost
> before governors can use the full advertised performance range.
> 
> Enable boost by default when at least one possible CPU reports support,
> while users who prefer to stay within the sustained nominal limit can
> still disable it via the boost knob without determining scaling_max_freq
> for each policy.
> 
> Check the performance capabilities before registering the driver so that
> the cpufreq core enables boost for each policy that supports it.
> 
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>


Just to be clear I'm not blocking this per se, but continuing my comments:

I just wonder if this is a configuration worth keeping.
You mentioned your platforms have a BIOS to set nominal==highest or not.
If we removed interpreting highest - nominal as boost entirely that
would also make that BIOS setting obsolete. Userspace could still
query nominal and restrict cpufreq to that if it wishes to do that,
we could add that to cpupower for convenience (i.e. set all policies'
max to nominal).

With the changes that are coming with CPCv4 we would save ourselves
some headache (like keeping track of boost status when ospm_nominal_perf
is being written).

The question is also how often the combination of "enable nominal < highest"
and then explicitly toggling boost at runtime actually happens...

> ---
> Changes in v2:
> - Drop "even" and clarify the commit message (Christian).
> - Link to v1: https://lore.kernel.org/all/20261015015812.867988-1-zhangpengjie2@huawei.com/
> 
>  drivers/cpufreq/cppc_cpufreq.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 80893844353c..0a4255a36f60 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -1052,6 +1052,25 @@ static struct cpufreq_driver cppc_cpufreq_driver = {
>  	.name = "cppc_cpufreq",
>  };
>  
> +static void __init cppc_cpufreq_default_boost_init(void)
> +{
> +	struct cppc_perf_caps caps;
> +	bool enable = false;
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (cppc_get_perf_caps(cpu, &caps))
> +			continue;
> +
> +		if (caps.highest_perf > caps.nominal_perf) {
> +			enable = true;
> +			break;
> +		}
> +	}
> +
> +	cppc_cpufreq_driver.boost_enabled = enable;

Any reason for the scan instead of just setting
boost_enabled = true? Platforms without boost would
also expose the toggle, but that's mostly in line with
the other drivers? (also again the ospm_nominal_perf
angle)

> +}
> +
>  static int __init cppc_cpufreq_init(void)
>  {
>  	int ret;
> @@ -1061,6 +1080,7 @@ static int __init cppc_cpufreq_init(void)
>  
>  	cppc_freq_invariance_init();
>  	populate_efficiency_class();
> +	cppc_cpufreq_default_boost_init();
>  
>  	ret = cpufreq_register_driver(&cppc_cpufreq_driver);
>  	if (ret)

Re: [PATCH v2] cpufreq: CPPC: Enable boost by default when supported

[Jie Zhan]

On 10/29/2026 4:51 AM, Christian Loehle wrote:
> On 10/22/26 08:59, Pengjie Zhang wrote:
>> The CPPC driver leaves boost disabled by default when Highest Performance
>> exceeds Nominal Performance. Userspace must explicitly enable boost
>> before governors can use the full advertised performance range.
>>
>> Enable boost by default when at least one possible CPU reports support,
>> while users who prefer to stay within the sustained nominal limit can
>> still disable it via the boost knob without determining scaling_max_freq
>> for each policy.
>>
>> Check the performance capabilities before registering the driver so that
>> the cpufreq core enables boost for each policy that supports it.
>>
>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> 
> 
> Just to be clear I'm not blocking this per se, but continuing my comments:
> 
> I just wonder if this is a configuration worth keeping.
> You mentioned your platforms have a BIOS to set nominal==highest or not.
> If we removed interpreting highest - nominal as boost entirely that
> would also make that BIOS setting obsolete. Userspace could still
> query nominal and restrict cpufreq to that if it wishes to do that,
> we could add that to cpupower for convenience (i.e. set all policies'
> max to nominal).
> 
> With the changes that are coming with CPCv4 we would save ourselves
> some headache (like keeping track of boost status when ospm_nominal_perf
> is being written).
That would be just some bonus functions.

I think the idea is to give userspace a knob to toggle boost on/off and
check the current status.

As of now, we don't have a better way to achieve this other than taking
highest > nominal.
> 
> The question is also how often the combination of "enable nominal < highest"
> and then explicitly toggling boost at runtime actually happens...
> 
In most cases, it's only set up once on boot.
Some experimental, debugging, or clever userspace strategies may toggle it
more often. Who knows :)

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