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

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Message-ID: <2099093.cPXO6Nhn9v@netbook>
Date:	Sun, 13 Jan 2013 13:34:41 +0100
From:	Thomas Schlichter <thomas.schlichter@....de>
To:	Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	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: [PATCH] cpuidle: fix new C-states not functional after AC disconnect

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!

Kind regards,
Thomas Schlichter
View attachment "0001-Get-power-info-before-updating-the-C-states.patch" of type "text/x-patch" (1016 bytes)

View attachment "0002-cpuidle-Initialize-power_usage-for-all-C-states.patch" of type "text/x-patch" (1265 bytes)