linux-kernel - Re: MCP limit log messages, 2.6.36-rc4

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Message-ID: <20100923145428.4805adcb@jbarnes-desktop>
Date:	Thu, 23 Sep 2010 14:54:28 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	tim.gardner@...onical.com
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: MCP limit log messages, 2.6.36-rc4

On Thu, 23 Sep 2010 13:48:16 -0700
Jesse Barnes <jbarnes@...tuousgeek.org> wrote:

> On Wed, 15 Sep 2010 11:47:45 -0600
> Tim Gardner <tim.gardner@...onical.com> wrote:
> 
> > I've been getting regular MCP limit log messages on a Dell Studio 1458 
> > (i5 CPU) with an A02 BIOS. With the attached debug hack it prints the 
> > following values:
> > 
> > [   33.605098] intel ips 0000:00:1f.6: MCP limit exceeded: Avg power 
> > 30123, limit 1023
> > [   38.597998] intel ips 0000:00:1f.6: MCP limit exceeded: Avg power 
> > 21697, limit 1023
> > [   43.590917] intel ips 0000:00:1f.6: MCP limit exceeded: Avg power 
> > 15390, limit 1023
> > [   48.583821] intel ips 0000:00:1f.6: MCP limit exceeded: Avg power 
> > 43370, limit 1023
> > [   53.576740] intel ips 0000:00:1f.6: MCP limit exceeded: Avg power 
> > 64728, limit 1023
> > 
> > This is an idle machine which starts printing these messages about 30 
> > seconds after boot. Any thoughts?
> 
> Actually, it looks like you have some non-upstream patches to the IPS
> driver, maybe one of Joe's patches to add more debug output when limits
> are exceeded?
> 
> At any rate, I think we're setting the MCP power limit incorrectly.
> The BIOS must be giving us a limit in 0.1W units (though even then it
> looks bogus); we need to clamp it to one of the available defaults.
> 
> Joe has some code for that as well, I've just asked him to update his
> patch, which we should get into 2.6.35.x.

Just posted some fixes for this to the x86 driver list, in particular
the "[PATCH 2/2] IPS driver: verify BIOS provided limits" should help a
bit here, but I still have a bug to fix in the i915 driver to really
make things work.

-- 
Jesse Barnes, Intel Open Source Technology Center
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