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

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Message-ID: <20100923134816.57e932fc@jbarnes-desktop>
Date:	Thu, 23 Sep 2010 13:48:16 -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 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.

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center
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