linux-kernel - Re: [PATCH] cpuidle: fix new C-states not functional after AC disconnect

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Message-ID: <2839069.gCgKnczmus@netbook>
Date:	Fri, 18 Jan 2013 23:24:22 +0100
From:	Thomas Schlichter <thomas.schlichter@....de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Len Brown <lenb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Andreas Müller <goo@...pelspeicher.org>,
	Julius Werner <jwerner@...omium.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuidle: fix new C-states not functional after AC disconnect

Dear Rafael,

I just recognized that I did not really describe the problem that my patch 
fixes. Therefore I attached the output of following command after disconnecting 
the AC power without and with my patch:

  grep -r "" /sys/devices/system/cpu/cpu0/cpuidle/

One can clearly see that some information is missing and the C3 state is not 
used.

Kind regards,
  Thomas

Am Freitag, 18. Januar 2013, 21:34:29 schrieb Thomas Schlichter:
> Dear Rafael,
> 
> thank you for applying Daniel's patch. I tested 3.8-rc4 and found that one
> patch ist still missing to fix the problem of not usable C-state after
> disconnect. I had it attached with my last e-mail as patch 1. For your
> conveniency, I have attached it here again.
> 
> With that patch the problem is fixed for me. So please consider applying
> this, too.
> 
> Kind regards,
>   Thomas
> 
> Am Sonntag, 13. Januar 2013, 21:04:45 schrieb Rafael J. Wysocki:
> > On Sunday, January 13, 2013 03:41:34 PM Daniel Lezcano wrote:
> > > On 01/13/2013 01:34 PM, Thomas Schlichter wrote:
> > > > Hi,
> > > > 
> > > > there is a long-standing regression about new C-states not working
> > > > after
> > > > disconnecting AC power from a laptop if the cpuidle driver "acpi-idle"
> > > > is
> > > > used. It was reported here:
> > > > 
> > > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=42870  (March 5th
> > > > 2012)
> > > > [2] https://bugzilla.kernel.org/show_bug.cgi?id=43349  (June 7th 2012)
> > > > [3] https://lkml.org/lkml/2012/10/16/518   (October 19th 2012)
> > > > 
> > > > In [1] Andreas proposed a patch that initialized the missing
> > > > power_usage
> > > > values from within acpi_idle in the same way as cpuidle does.
> > > > In [2] I proposed a patch to use the power values provided by ACPI to
> > > > initialize the power_usage variables.
> > > > In [3] Julius proposed a patch to call the initialization function
> > > > set_power_states()  not only once, but always when the C-states
> > > > change.
> > > > 
> > > > Currently, Daniel Lezcano seems to be working on an intrusive change
> > > > of
> > > > not
> > > > using the power_usage value at all for choosing a C-state:
> > > > 
> > > > [4] https://lkml.org/lkml/2012/12/14/155
> > > > 
> > > > As I could not find any of these patches in any git trees to be merged
> > > > for
> > > > 3.8, I propose an other, least intrusive patch for the time being. It
> > > > is
> > > > attached an initializes _all_ power_usage values in the first place.
> > > > 
> > > > As this is a real power consumption regression since 3.2, I really ask
> > > > you to apply anything and push it to stable, too!
> > > 
> > > Rafael, is possible to apply the patch [1/2] I previously sent ?
> > > 
> > > https://patchwork.kernel.org/patch/1878691/
> > 
> > I need to talk about this with Len.  That should happen tomorrow if
> > everything goes well.
> > 
> > > So we get this bug fixed.
> > > 
> > > I will resend the patch [2/2] as soon as possible.
> > 
> > OK
> > 
> > Thanks,
> > Rafael
View attachment "cpuidle_3.8-rc4.txt" of type "text/plain" (1545 bytes)

View attachment "cpuidle_3.8-rc4_patched.txt" of type "text/plain" (1559 bytes)