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

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Date:	Fri, 10 Jun 2016 03:22:26 -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> [160509 13:52]:
> 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 :).

OK. And I just applied the related dts changes. Please repost the driver
changes and DT binding doc with Rob's ack to the driver maintainers to
apply.

Regards,

Tony