linux-kernel - Re: [PATCH v2] PM / Domains: Skip timings during syscore suspend/resume

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Message-ID: <3117326.C9gLKzzTZ1@vostro.rjw.lan>
Date:	Tue, 16 Jun 2015 01:41:05 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Kevin Hilman <khilman@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH v2] PM / Domains: Skip timings during syscore suspend/resume

On Friday, May 29, 2015 05:24:23 PM Geert Uytterhoeven wrote:
> From: Geert Uytterhoeven <geert+renesas@...der.be>
> 
> The PM Domain code uses ktime_get() to perform various latency
> measurements.  However, if ktime_get() is called while timekeeping is
> suspended, the following warning is printed:
> 
>     WARNING: CPU: 0 PID: 1340 at kernel/time/timekeeping.c:576 ktime_get+0x3
> 
> This happens when resuming the PM Domain that contains the clock events
> source, which calls pm_genpd_syscore_poweron(). Chain of operations is:
> 
>     timekeeping_resume()
>     {
> 	clockevents_resume()
> 	    sh_cmt_clock_event_resume()
> 		pm_genpd_syscore_poweron()
> 		    pm_genpd_sync_poweron()
> 			genpd_syscore_switch()
> 			    genpd_power_on()
> 				ktime_get(), but timekeeping_suspended == 1
> 	...
> 	timekeeping_suspended = 0;
>     }
> 
> Fix this by adding a "timed" parameter to genpd_power_{on,off}() and
> pm_genpd_sync_power{off,on}(), to indicate whether latency measurements
> are allowed.  This parameter is passed as false in
> genpd_syscore_switch() (i.e. during syscore suspend/resume), and true in
> all other cases.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Queued up for 4.2, thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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