linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Fix setting max_perf

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Message-ID: <543FDEC8.1080102@gmail.com>
Date:	Thu, 16 Oct 2014 08:05:44 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Pali Rohár <pali.rohar@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>
CC:	dirk.brandewie@...il.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Fix setting max_perf_pct in performance
 policy

On 10/15/2014 04:16 PM, Pali Rohár wrote:
> Code which changes policy to powersave changes also max_policy_pct based on
> max_freq. Code which change max_perf_pct has upper limit base on value
> max_policy_pct. When policy is changing from powersave back to performance
> then max_policy_pct is not changed. Which means that changing max_perf_pct is
> not possible to high values if max_freq was too low in powersave policy.
>
> Test case:
>
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
> 800000
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> 3300000
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> performance
> $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 100
>
> $ echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> $ echo 800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> $ echo 20 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
>
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> powersave
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> 800000
> $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 20
>
> $ echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> $ echo 3300000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> $ echo 100 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
>
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> performance
> $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> 3300000
> $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 24
>
> And now intel_pstate driver allows to set maximal value for max_perf_pct based
> on max_policy_pct which is 24 for previous powersave max_freq 800000.
>
> This patch will set default value for max_policy_pct when setting policy to
> performance so it will allow to set also max value for max_perf_pct.
>
> Signed-off-by: Pali Rohár <pali.rohar@...il.com>

Acked-by: Dirk Brandewie <dirk.j.brandewie@...el.com>

> Cc: stable@...r.kernel.org
> ---
>   drivers/cpufreq/intel_pstate.c |    1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 0668b38..7547ab5 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -714,6 +714,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>   	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE) {
>   		limits.min_perf_pct = 100;
>   		limits.min_perf = int_tofp(1);
> +		limits.max_policy_pct = 100;
>   		limits.max_perf_pct = 100;
>   		limits.max_perf = int_tofp(1);
>   		limits.no_turbo = limits.turbo_disabled;
>

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