linux-kernel - Re: [PATCH 0/5] Add suspend-to-idle validation for Intel SoCs

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Date:	Tue, 7 Jun 2016 17:07:21 -0700
From:	"dbasehore ." <dbasehore@...omium.org>
To:	Pavel Machek <pavel@....cz>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/5] Add suspend-to-idle validation for Intel SoCs

On Tue, Jun 7, 2016 at 12:46 AM, Pavel Machek <pavel@....cz> wrote:
> On Wed 2016-06-01 21:33:24, dbasehore@...omium.org wrote:
>> From: Derek Basehore <dbasehore@...omium.org>
>>
>> This patch set adds support for catching errors when entering freeze
>> on Intel Skylake SoCs. Support for this can be added to newer SoCs in
>> later patches.
>>
>> Verification is done by waking up the CPU once every X (default 10)
>> seconds to check the residency of S0ix. This can't be verified before
>> attempting to enter S0ix through mwait, so we have to repeatedly
>> verify entry into that state. Successfully entering S0ix is no
>> guarantee that it will be entered on the next attempt, so we have to
>> schedule another check. This has a minimal power impact of <1% of the
>> total system power on our systems.
>
> Dunno. Should this be protected with something like CONFIG_TEST_SLEEP?
> People probably don't want this for production...
>

That depends, if you switch to using suspend to idle instead of
suspend to RAM, would you rather not catch power bugs due to
misconfigured hardware in production?

I agree that it shouldn't be on by default since freeze shouldn't fail
because some IP on the SoC doesn't have firmware loaded (this happens
with i915), but I was just going to leave it off by default instead of
adding yet another config option for a small feature.

> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html