linux-kernel - Re: [PATCH 5/7] ARM: OMAP: dmtimer: Do not call PM runtime functions when not needed.

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Date:	Mon, 9 May 2016 23:51:12 +0300
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	thierry.reding@...il.com, bcousson@...libre.com,
	linux@....linux.org.uk, mchehab@....samsung.com,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
	sre@...nel.org, pali.rohar@...il.com
Subject: Re: [PATCH 5/7] ARM: OMAP: dmtimer: Do not call PM runtime functions
 when not needed.

Hi,

On  9.05.2016 22:36, Tony Lindgren wrote:
> * Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com> [160507 08:24]:
>> once omap_dm_timer_start() is called, which calls omap_dm_timer_enable()
>> and thus pm_runtime_get_sync(), it doesn't make sense to call PM runtime
>> functions again before omap_dm_timer_stop is called(). Otherwise PM runtime
>> functions called in omap_dm_timer_enable/disable lead to long and unneeded
>> delays.
>>
>> Fix that by implementing an "enabled" counter, so the PM runtime functions
>> get called only when really needed.
>>
>> Without that patch Nokia N900 IR TX driver (ir-rx51) does not function.
>

Well, I just tested again, with the $subject patch reverted and 
contradictory to my own words, it worked just fine. I believe the reason 
is that I did hrtimer "migration" after I did the $subject patch. I was 
thinking the reason for the slow transmission was PWM dmtimer, but now 
it turns out it has been the "pulse" dmtimer. So, I think the $subject 
patch should be dropped.

> We should use pm_runtime for the refcounting though and call PM runtime
> unconditionally. Can you try to follow the standard PM runtime usage
> like this:
>

It works without that, but on the other hand, I finally have some 
reference on how PM runtime API should be called :).

> init:
> pm_runtime_use_autosuspend(&timer->pdev->dev);
> pm_runtime_set_autosuspend_delay(&timer->pdev->dev, 200);
> pm_runtime_enable(&timer->pdev->dev);
> ...
> enable:
> pm_runtime_get_sync(&timer->pdev->dev);
> ...
> disable:
> pm_runtime_mark_last_busy(&timer->pdev->dev);
> pm_runtime_put_autosuspend(&timer->pdev->dev);
> ...
> exit:
> pm_runtime_dont_use_autosuspend(&timer->pdev->dev);
> pm_runtime_put_sync(&timer->pdev->dev);
> pm_runtime_disable(&timer->pdev->dev);
>
> No idea what the timeout should be, maybe less than 200 ms. Also we need
> to test that off idle still works with timer1, that might need special
> handling.
>

Thanks,
Ivo