[PATCH] cpufreq: intel_pstate: set stale CPU frequency to minimum

[PATCH] cpufreq: intel_pstate: set stale CPU frequency to minimum

[Keyon Jie]

From: Doug Smythies <dsmythies@telus.net>

commit d51847acb018d83186e4af67bc93f9a00a8644f7 upstream.

This fix applies to all stable kernel versions 5.18+.

The intel_pstate CPU frequency scaling driver does not
use policy->cur and it is 0.
When the CPU frequency is outdated arch_freq_get_on_cpu()
will default to the nominal clock frequency when its call to
cpufreq_quick_getpolicy_cur returns the never updated 0.
Thus, the listed frequency might be outside of currently
set limits. Some users are complaining about the high
reported frequency, albeit stale, when their system is
idle and/or it is above the reduced maximum they have set.

This patch will maintain policy_cur for the intel_pstate
driver at the current minimum CPU frequency.

Reported-by: Yang Jie <yang.jie@linux.intel.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217597
Signed-off-by: Doug Smythies <dsmythies@telus.net>
[ rjw: White space damage fixes and comment adjustment ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
---
 drivers/cpufreq/intel_pstate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index d51f90f55c05..fbe3a4098743 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2574,6 +2574,11 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 			intel_pstate_clear_update_util_hook(policy->cpu);
 		intel_pstate_hwp_set(policy->cpu);
 	}
+	/*
+	 * policy->cur is never updated with the intel_pstate driver, but it
+	 * is used as a stale frequency value. So, keep it within limits.
+	 */
+	policy->cur = policy->min;
 
 	mutex_unlock(&intel_pstate_limits_lock);
 
-- 
2.34.1

Re: [PATCH] cpufreq: intel_pstate: set stale CPU frequency to minimum

[Greg Kroah-Hartman]

On Tue, Sep 05, 2023 at 05:16:46PM -0700, Keyon Jie wrote:
> From: Doug Smythies <dsmythies@telus.net>
> 
> commit d51847acb018d83186e4af67bc93f9a00a8644f7 upstream.
> 
> This fix applies to all stable kernel versions 5.18+.
> 
> The intel_pstate CPU frequency scaling driver does not
> use policy->cur and it is 0.
> When the CPU frequency is outdated arch_freq_get_on_cpu()
> will default to the nominal clock frequency when its call to
> cpufreq_quick_getpolicy_cur returns the never updated 0.
> Thus, the listed frequency might be outside of currently
> set limits. Some users are complaining about the high
> reported frequency, albeit stale, when their system is
> idle and/or it is above the reduced maximum they have set.
> 
> This patch will maintain policy_cur for the intel_pstate
> driver at the current minimum CPU frequency.
> 
> Reported-by: Yang Jie <yang.jie@linux.intel.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217597
> Signed-off-by: Doug Smythies <dsmythies@telus.net>
> [ rjw: White space damage fixes and comment adjustment ]
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 5 +++++
>  1 file changed, 5 insertions(+)

What stable kernel(s) is this for?

Re: [PATCH] cpufreq: intel_pstate: set stale CPU frequency to minimum

[Keyon Jie]

On 9/6/23 01:38, Greg Kroah-Hartman wrote:
> On Tue, Sep 05, 2023 at 05:16:46PM -0700, Keyon Jie wrote:
>> From: Doug Smythies <dsmythies@telus.net>
>>
>> commit d51847acb018d83186e4af67bc93f9a00a8644f7 upstream.
>>
>> This fix applies to all stable kernel versions 5.18+.
>>
>> The intel_pstate CPU frequency scaling driver does not
>> use policy->cur and it is 0.
>> When the CPU frequency is outdated arch_freq_get_on_cpu()
>> will default to the nominal clock frequency when its call to
>> cpufreq_quick_getpolicy_cur returns the never updated 0.
>> Thus, the listed frequency might be outside of currently
>> set limits. Some users are complaining about the high
>> reported frequency, albeit stale, when their system is
>> idle and/or it is above the reduced maximum they have set.
>>
>> This patch will maintain policy_cur for the intel_pstate
>> driver at the current minimum CPU frequency.
>>
>> Reported-by: Yang Jie <yang.jie@linux.intel.com>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217597
>> Signed-off-by: Doug Smythies <dsmythies@telus.net>
>> [ rjw: White space damage fixes and comment adjustment ]
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
>> ---
>>   drivers/cpufreq/intel_pstate.c | 5 +++++
>>   1 file changed, 5 insertions(+)
> 
> What stable kernel(s) is this for?

Sorry missed it. We need it for all 5.18+ kernel, but I have only 
verified it on linux-6.1.y.

Thanks,
~Keyon

Re: [PATCH] cpufreq: intel_pstate: set stale CPU frequency to minimum

[Greg Kroah-Hartman]

On Tue, Sep 05, 2023 at 05:16:46PM -0700, Keyon Jie wrote:
> From: Doug Smythies <dsmythies@telus.net>
> 
> commit d51847acb018d83186e4af67bc93f9a00a8644f7 upstream.
> 
> This fix applies to all stable kernel versions 5.18+.
> 
> The intel_pstate CPU frequency scaling driver does not
> use policy->cur and it is 0.
> When the CPU frequency is outdated arch_freq_get_on_cpu()
> will default to the nominal clock frequency when its call to
> cpufreq_quick_getpolicy_cur returns the never updated 0.
> Thus, the listed frequency might be outside of currently
> set limits. Some users are complaining about the high
> reported frequency, albeit stale, when their system is
> idle and/or it is above the reduced maximum they have set.
> 
> This patch will maintain policy_cur for the intel_pstate
> driver at the current minimum CPU frequency.
> 
> Reported-by: Yang Jie <yang.jie@linux.intel.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217597
> Signed-off-by: Doug Smythies <dsmythies@telus.net>
> [ rjw: White space damage fixes and comment adjustment ]
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index d51f90f55c05..fbe3a4098743 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -2574,6 +2574,11 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>  			intel_pstate_clear_update_util_hook(policy->cpu);
>  		intel_pstate_hwp_set(policy->cpu);
>  	}
> +	/*
> +	 * policy->cur is never updated with the intel_pstate driver, but it
> +	 * is used as a stale frequency value. So, keep it within limits.
> +	 */
> +	policy->cur = policy->min;
>  
>  	mutex_unlock(&intel_pstate_limits_lock);
>  

Now queued up, thanks.

greg k-h