linux-kernel - Re: Possible bug in eeepc-laptop.c

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Date:	Thu, 11 Mar 2010 22:28:50 +0100
From:	Fabio Comolli <fabio.comolli@...il.com>
To:	ACPI mailing list <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Corentin Chary <corentin.chary@...il.com>
Cc:	Len Brown <lenb@...nel.org>
Subject: Re: Possible bug in eeepc-laptop.c - EeePC 900

Hi.

On Tue, Mar 9, 2010 at 11:58 PM, Fabio Comolli <fabio.comolli@...il.com> wrote:
> Hi.
> I have an EeePC 900 running 2.6.34-rc1.
>
> If I boot it on AC the cpu runs at full speed, 900MHz; if I boot it on
> battery it runs only at 630Mhz. Plugging / unplugging the AC does not
> change the cpu frequency. Only a reboot can change the situation.
>
> I already tried to echo 0 or 1 to the
> /sys/devices/platform/eeepc/cpufv file; no effects, even if the file
> changes its value.
>
> This is not a regression from 2.6.33: this behavior is also present in
> that version.
>
> Does this ring any bells? This is really annoying, especially when
> trying to watch a movie on battery. Also 3D apps show a 30%
> performance drop, as expected.
>
> Regards,
> Fabio

Well, it turns out that this is indeed a regression, but I don't know
from which kernel version.
I reverted (not cleanly) this patch:

        http://patchwork.kernel.org/patch/28591

and now

        echo 1 > /sys/devices/platform/eeepc/cpufv

enables the powersave mode and

        echo 0 > /sys/devices/platform/eeepc/cpufv

enables the performance mode.

Tested with the non-benchmark glxgears (275 frames/sec in powersave
mode and 405 in performance mode) and stellarium (14 frames and 20
frames).

Regards,
Fabio
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