linux-kernel - Re: [PATCH V2] cpufreq: respect the min/max settings from user space

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Message-ID: <4263460.gtRjLEEEsM@vostro.rjw.lan>
Date:	Sat, 15 Nov 2014 00:56:41 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Vince Hsu <vinceh@...dia.com>
Cc:	viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, =bilhuang@...dia.com,
	dgreid@...gle.com, olofj@...omium.org
Subject: Re: [PATCH V2] cpufreq: respect the min/max settings from user space

On Monday, November 10, 2014 02:14:50 PM Vince Hsu wrote:
> When the user space tries to set scaling_(max|min)_freq through
> sysfs, the cpufreq_set_policy() asks other driver's opinions
> for the max/min frequencies. Some device drivers, like Tegra
> CPU EDP which is not upstreamed yet though, may constrain the
> CPU maximum frequency dynamically because of board design.
> So if the user space access happens and some driver is capping
> the cpu frequency at the same time, the user_policy->(max|min)
> is overridden by the capped value, and that's not expected by
> the user space. And if the user space is not invoked again,
> the CPU will always be capped by the user_policy->(max|min)
> even no drivers limit the CPU frequency any more.
> 
> This patch preserves the user specified min/max settings, so that
> every time the cpufreq policy is updated, the new max/min can
> be re-evaluated correctly based on the user's expection and
> the present device drivers' status.
> 
> Signed-off-by: Vince Hsu <vinceh@...dia.com>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

Queued up for 3.19, thanks!

> ---
> v2: added Viresh's Acked-by
> 
>  drivers/cpufreq/cpufreq.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 644b54e1e7d1..0721ab352e2a 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -535,7 +535,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
>  static ssize_t store_##file_name					\
>  (struct cpufreq_policy *policy, const char *buf, size_t count)		\
>  {									\
> -	int ret;							\
> +	int ret, temp;							\
>  	struct cpufreq_policy new_policy;				\
>  									\
>  	ret = cpufreq_get_policy(&new_policy, policy->cpu);		\
> @@ -546,8 +546,10 @@ static ssize_t store_##file_name					\
>  	if (ret != 1)							\
>  		return -EINVAL;						\
>  									\
> +	temp = new_policy.object;					\
>  	ret = cpufreq_set_policy(policy, &new_policy);		\
> -	policy->user_policy.object = policy->object;			\
> +	if (!ret)							\
> +		policy->user_policy.object = temp;			\
>  									\
>  	return ret ? ret : count;					\
>  }
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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