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Date:   Mon, 11 Feb 2019 13:36:02 -0800
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Lukasz Luba <l.luba@partner.samsung.com>
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        b.zolnierkie@samsung.com, myungjoo.ham@samsung.com,
        cw00.choi@samsung.com, kyungmin.park@samsung.com,
        m.szyprowski@samsung.com, s.nawrocki@samsung.com, tkjos@google.com,
        joel@joelfernandes.org, chris.diamand@arm.com
Subject: Re: [PATCH v2 2/2] drivers: devfreq: change deferred work into
 delayed
Message-ID: <20190211213602.GQ117604@google.com>
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Hi Lukasz,

On Mon, Feb 11, 2019 at 04:30:05PM +0100, Lukasz Luba wrote:
> This patch changes deferred work to delayed work, which is now not missed
> when timer is put on CPU that entered idle state.
> The devfreq framework governor was not called, thus changing the device's
> frequency did not happen.
> Benchmarks for stressing Dynamic Memory Controller show x2 (in edge cases
> even x5) performance boost with this patch when 'simpleondemand_governor'
> is responsible for monitoring the device load and frequency changes.
> 
> With this patch, the delayed work is done no mater CPUs' idle.
> All of the drivers in devfreq which rely on periodic, guaranteed wakeup
> intervals should benefit from it.
> 
> Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 882e717..c200b3c 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -400,7 +400,7 @@ static void devfreq_monitor(struct work_struct *work)
>   */
>  void devfreq_monitor_start(struct devfreq *devfreq)
>  {
> -	INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> +	INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
>  	if (devfreq->profile->polling_ms)
>  		schedule_delayed_work(&devfreq->work,
>  			msecs_to_jiffies(devfreq->profile->polling_ms));

I'd suggest to swap the order of the patches in this series.

Why, you may ask, if the end product is the same? This patch ([2/2])
fixes an actual problem, while IIUC [1/2] is just an improvement, the
fix doesn't really depend on it. If -stable wants to integrate the
fix, they also need to pick the improvement (or resolve a conflict),
which might not be desired.

Otherwise this looks sane to me:

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>