linux-kernel - Re: [PATCH V3 4/5] cpufreq: Register notifiers with the PM QoS framework

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Message-ID: <20190614164641.GP137143@google.com>
Date:   Fri, 14 Jun 2019 09:46:41 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Qais.Yousef@....com, juri.lelli@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 4/5] cpufreq: Register notifiers with the PM QoS
 framework

Hi Viresh,

On Mon, Jun 10, 2019 at 04:21:35PM +0530, Viresh Kumar wrote:
> This registers the notifiers for min/max frequency constraints with the
> PM QoS framework. The constraints are also taken into consideration in
> cpufreq_set_policy().
> 
> This also relocates cpufreq_policy_put_kobj() as it is required to be
> called from cpufreq_policy_alloc() now.
> 
> No constraints are added until now though.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 139 +++++++++++++++++++++++++++++++-------
>  include/linux/cpufreq.h   |   4 ++
>  2 files changed, 120 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 85ff958e01f1..547d221b2ff2 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -26,6 +26,7 @@
>  #include <linux/kernel_stat.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> +#include <linux/pm_qos.h>
>  #include <linux/slab.h>
>  #include <linux/suspend.h>
>  #include <linux/syscore_ops.h>
> @@ -1126,11 +1127,77 @@ static void handle_update(struct work_struct *work)
>  	cpufreq_update_policy(cpu);
>  }
>  
> +static void cpufreq_update_freq_work(struct work_struct *work)
> +{
> +	struct cpufreq_policy *policy =
> +		container_of(work, struct cpufreq_policy, req_work);
> +	struct cpufreq_policy new_policy = *policy;
> +
> +	/* We should read constraint values from QoS layer */
> +	new_policy.min = 0;
> +	new_policy.max = UINT_MAX;
> +
> +	down_write(&policy->rwsem);
> +
> +	if (!policy_is_inactive(policy))
> +		cpufreq_set_policy(policy, &new_policy);
> +
> +	up_write(&policy->rwsem);
> +}
> +
> +static int cpufreq_update_freq(struct cpufreq_policy *policy)
> +{
> +	schedule_work(&policy->req_work);

I think you need to add a cancel_work_sync() in cpufreq_policy_free()
to make sure the work doesn't run after the policy has been freed.

Otherwise it looks good to me.

Cheers

Matthias