linux-kernel - Re: [PATCH V2] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)

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Date:   Tue, 29 May 2018 15:56:38 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Kevin Wangtao <kevin.wangtao@...ilicon.com>
Cc:     rjw@...ysocki.net, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, gengyanping@...ilicon.com,
        sunzhaosheng@...ilicon.com
Subject: Re: [PATCH V2] cpufreq: reinitialize new policy min/max when writing
 scaling_(max|min)_freq

On 26-05-18, 15:16, Kevin Wangtao wrote:
> consider such situation, current user_policy.min is 1000000,
> current user_policy.max is 1200000, in cpufreq_set_policy,
> other driver may update policy.min to 1200000, policy.max to
> 1300000. After that, If we input "echo 1300000 > scaling_min_freq",
> then user_policy.min will be 1300000, and user_policy.max is
> still 1200000, because the input value is checked with policy.max
> not user_policy.max. if we get all related cpus offline and
> online again, it will cause cpufreq_init_policy fail because
> user_policy.min is higher than user_policy.max.
> 
> The solution is when user space tries to write scaling_(max|min)_freq,
> the min/max of new_policy should be reinitialized with min/max
> of user_policy, like what cpufreq_update_policy does.
> 
> Signed-off-by: Kevin Wangtao <kevin.wangtao@...ilicon.com>
> ---
>  drivers/cpufreq/cpufreq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index b79c532..82123a1 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -697,6 +697,8 @@ static ssize_t store_##file_name					\
>  	struct cpufreq_policy new_policy;				\
>  									\
>  	memcpy(&new_policy, policy, sizeof(*policy));			\

Maybe add a comment here on why this is required ?

> +	new_policy.min = policy->user_policy.min;			\
> +	new_policy.max = policy->user_policy.max;			\
>  									\
>  	ret = sscanf(buf, "%u", &new_policy.object);			\
>  	if (ret != 1)							\

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh