linux-kernel - Re: [PATCH] PM / sleep: add configurable delay for pm

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Message-ID: <CAJFHJroY_uBdRPVBPgCggchpAQ1n+jb=QjzNvy0cP-WLmsAPNA@mail.gmail.com>
Date:	Thu, 4 Sep 2014 19:11:23 -0700
From:	Chirantan Ekbote <chirantan@...omium.org>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] PM / sleep: add configurable delay for pm_test

On Thu, Sep 4, 2014 at 10:54 AM, Brian Norris
<computersforpeace@...il.com> wrote:
> On Thu, Sep 04, 2014 at 09:14:12AM +0200, Pavel Machek wrote:
>> > When CONFIG_PM_DEBUG=y, we provide a sysfs file (/sys/power/pm_test) for
>> > selecting one of a few suspend test modes, where rather than entering a
>> > full suspend state, the kernel will perform some subset of suspend
>> > steps, wait 5 seconds, and then resume back to normal operation.
>> >
>> > This mode is useful for (among other things) observing the state of the
>> > system just before entering a sleep mode, for debugging or analysis
>> > purposes. However, a constant 5 second wait is not sufficient for some
>> > sorts of analysis; for example, on an SoC, one might want to use
>> > external tools to probe the power states of various on-chip controllers
>> > or clocks.
>>
>> When you are doing this kind of analysis, perhaps directly modifying
>> kernel source is the way to go ...?
>
> That's what I've been doing for now, but I have a few engineers who need
> to do this sort of testing and aren't kernel developers. I could
> continue to maintain my own patch for this, but I just thought I'd see
> what others thought.
>
> Is there a good reason this can't be in mainline? These features are
> hidden behind a Kconfig symbol called PM_DEBUG anyway, and I think this
> classifies as a pretty simple extension to the limited existing PM
> debugging options.
>

We're currently carrying a similar patch in the chrome os kernel tree.
I would also like to see this go into mainline.

-Chirantan

> Regards,
> Brian
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