linux-kernel - Re: [PATCH v2 1/5] power: domain: add pm_genpd

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Message-ID: <CAPDyKFpSu=vik3kDn9zrv7dkg5n+Dqe+xs4FZnB8nhTA=ahaAg@mail.gmail.com>
Date:	Mon, 14 Dec 2015 10:49:07 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Alexander Aring <alex.aring@...il.com>,
	Eric Anholt <eric@...olt.net>,
	Jon Hunter <jonathanh@...dia.com>
Cc:	Kevin Hilman <khilman@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Pawel Moll <pawel.moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Lee Jones <lee@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	linux-rpi-kernel@...ts.infradead.org, Pavel Machek <pavel@....cz>,
	Len Brown <len.brown@...el.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [PATCH v2 1/5] power: domain: add pm_genpd_exit

+Russell

[...]

>> >> +void pm_genpd_exit(struct generic_pm_domain *genpd)
>> >> +{
>> >> +  if (IS_ERR_OR_NULL(genpd))
>> >> +          return;
>> >> +
>> >> +  /* check if domain is still in registered inside the pm subsystem */
>> >> +  WARN_ON_ONCE(!list_empty(&genpd->master_links) ||
>> >> +               !list_empty(&genpd->slave_links) ||
>> >> +               !list_empty(&genpd->dev_list));
>> >> +
>> >
>> > Why not return an error here? Seems bad to remove it, if it could still
>> > be referenced by other domains.
>>
>> I had pointed this out as well in an earlier review.
>>
>
> I talked with Ulf Hansson about such handling and there exists currently
> no handling to remove the pm_genpd on error handling (what our use case
> is for RPi domains).
>
> The real solution would be a "pm_genpd_exit_recursive" functionality to
> remove subdomains, etc -> simple everything. Anway I am not a expert into
> power domain functionality and this simple approach was enough to him to
> add "something" which we have actually a lack of support.
>
>

[...]

Just to be clear on my view. I think Russell made a good summary of
how we should implement this API [1].
We should return an error, instead of WARN_ON_ONCE and continue.

Perhaps you can do both a WARN *and* return an error.

Regarding the similar patch from Jon Hunter, I would suggest we focus
on Alexander's $subject patch and try to it queued for 4.5. Please
send a new version.

Also, as other SoC genpd driver isn't using a "pm_genpd_exit()" API,
it shouldn't prevent neither Alexander/Eric or Jon from proceeding
with the RPI/Tegra genpd drivers. Once the new API is in place you can
update these drivers to properly deal with error handling and undo
things from pm_genpd_init().

Kind regards
Uffe

[1]
https://lkml.org/lkml/2015/12/9/308
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