linux-kernel - Athlon L110 CPU and powernow-k8

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Message-ID: <DDE95BDD51FB774B804A9C029E735EE103E9BF5129@sausexmbp02.amd.com>
Date:	Mon, 19 Apr 2010 06:43:48 -0700
From:	"Langsdorf, Mark" <mark.langsdorf@....com>
To:	"'joss@...ian.org'" <joss@...ian.org>
CC:	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: Athlon L110 CPU and powernow-k8


> Date: Fri, 16 Apr 2010 22:40:58 +0200
> From: Josselin Mouette <joss@...ian.org>
> To: linux-kernel@...r.kernel.org
> Subject: Athlon L110 CPU and powernow-k8
> X-Mailer: Evolution 2.29.92.1
> Message-ID: <1271450458.6794.33.camel@...oyo>
> 
> In both cases, the issue is the same: the DSDT table provided by the
> BIOS does not include the P-states. Waiting for a hypothetical BIOS
> update that would fix this bug requires some faith that I 
> don't have. It is possible to work around this by compiling the
> kernel with a custom DSDT table with appropriate P-states patched
> in, however I consider this a developer hack. 
>
> I wonder what is possible to do to support this CPU correctly in the
> kernel. The only sane solution I can think of is to hardcode the
> P-states for this CPU model in the powernow-k8 driver itself. 

I think that hard-coding P-states into the PowerNow 
driver is not a mantainable solution.

I don't quite understand why the you think that
a custom DSDT as a BIOS hack, but think that
adding custom frequencies to the driver itself is
acceptable.

The last time this issue came up on cpufreq, Dave
Jones nixed a general solution to add custom P-states
through the driver on the grounds that people would
undervolt their systems, causing a lot of screwy,
unpredictable behavior.  I agreed with his opinion
then and I don't see anything in this mesage to
change that view.


--Mark Langsdorf
Operating System Research Center
AMD

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