linux-kernel - Re: [PATCH] [RFC] cpufreq: can't raise max frequency with cpu

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Date:	Tue, 18 Dec 2012 20:17:53 -0800
From:	amit daniel kachhap <amit.daniel@...sung.com>
To:	Sonny Rao <sonnyrao@...omium.org>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Zhang Rui <rui.zhang@...el.com>,
	Doug Anderson <dianders@...omium.org>,
	Sameer Nanda <snanda@...omium.org>
Subject: Re: [PATCH] [RFC] cpufreq: can't raise max frequency with cpu_thermal

On Tue, Dec 18, 2012 at 12:29 AM, Sonny Rao <sonnyrao@...omium.org> wrote:
> The cpu_thermal generic thermal management code has a bug where once
> max cpu frequency has been lowered in sysfs (scaling_max_freq) it is
> not possible to raise the max back up later.  The bug is that the
> notifer gets called by __cpufreq_set_policy() before the user policy
> max is raised, and is incorrectly trying to enforce the max frequency
> policy even when we are trying to change the policy.  It is also not
> clear why this driver is looking at the user policy since it is
> primarily supposed to enforce thermal policy, not user set policy.

Hi Sunny,

I am not sure if this change is needed.
There is a check in cpufreq_thermal_notifier function to return 0 if
notify_device == NOTIFY_INVALID. So the user will be always able to
change the max frequency in normal situation. Did you tested this for
some corner cases?
The reason behind putting this check is that I don't want to override
the user constraints.

Thanks,
Amit Daniel

>
> Signed-off-by: Sonny Rao <sonnyrao@...omium.org>
> ---
>  drivers/thermal/cpu_cooling.c |    4 ----
>  1 files changed, 0 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index 836828e..63bc708 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -219,10 +219,6 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb,
>         if (cpumask_test_cpu(policy->cpu, &notify_device->allowed_cpus))
>                 max_freq = notify_device->cpufreq_val;
>
> -       /* Never exceed user_policy.max*/
> -       if (max_freq > policy->user_policy.max)
> -               max_freq = policy->user_policy.max;
> -
>         if (policy->max != max_freq)
>                 cpufreq_verify_within_limits(policy, 0, max_freq);
>
> --
> 1.7.7.3
>
> --
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