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

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Message-ID: <20160509193624.GH5995@atomide.com>
Date:	Mon, 9 May 2016 12:36:24 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.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.

* 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.

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:

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.

Regards,

Tony