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

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Message-ID: <4C9BD8D5.7080201@canonical.com>
Date:	Fri, 24 Sep 2010 06:46:45 +0800
From:	Tim Gardner <tim.gardner@...onical.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: MCP limit log messages, 2.6.36-rc4

On 09/24/2010 05:54 AM, Jesse Barnes wrote:
> 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?
>>

Its just a debug hack which I wrote (that I mentioned in the first 
email) so I could figure out why the driver was complaining.

>> 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.
>

I'll be back from Asia by Monday and will give these patches a try.

rtg
-- 
Tim Gardner tim.gardner@...onical.com
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