linux-kernel - Re: [linux-pm] sleepy linux self-test

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Date:	Sun, 03 Feb 2008 15:08:26 -0800
From:	David Brownell <david-b@...bell.net>
To:	pavel@....cz
Cc:	rjw@...k.pl, mingo@...e.hu, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] sleepy linux self-test

> > > The changes look good to me.
> > 
> > They feel unfinished to me though.  :)
> > 
> > Like using "jiffies" instead of a clocksource, which makes trouble
> > since the timing covers periods with IRQs disabled.  And the test
> > mode parameter needs work.
>
> Well, I'd say that timing has bigger problem, right?
>
> It is
>
> set alarm
> 	suspend system
> | poweroff
> alarm expires
> 	system resumes
>
> ... so you are measuring resume time + sleep time, no? 

There's no "poweroff" step when entering STR or STANDBY!

But more specifically, I avoided that issue by comparing times between
  (a) start and end of the "suspend devices" steps;
  (b) start and end of the "resume devices" steps.

Example output, with the relevant lines highlighted by "*":

    PM: test RTC wakeup from 'mem' suspend
    PM: Syncing filesystems ... done.
    PM: Preparing system for mem sleep
    Freezing user space processes ... (elapsed 0.00 seconds) done.
    Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done.
    PM: Entering mem sleep
    Suspending console(s)
 *  PM: suspend devices took 0.000 seconds
    GPIO-A may wake for 00080000
    GPIO-C may wake for 00000008
    GPIO-D may wake for 00000020
    AT91: PM - wake mask 00000036, pm state 3
    AT91: PM - no slow clock mode yet ...
    AT91: PM - wakeup 00000002
 *  PM: resume devices took 0.132 seconds
    PM: Finishing wakeup.
    Restarting tasks ... done.

The underlying clocksource has resolution of 32 KiHz, while HZ=128;
the "suspend" more typically reports 7 msec.  And there should be a
few more wakeup GPIOs, except I seem to not have enabled gpio_keys.
That "wakeup 00000002" means the heavily-overloaded "system" IRQ
woke the system ... the RTC is on that IRQ line.

- Dave

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