linux-kernel - Re: coretemp: Support for Intel Atom E6XX CPU (TunnelCreek)?

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Date:	Mon, 27 Jun 2011 09:10:54 -0700
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	Jean Delvare <khali@...ux-fr.org>
CC:	Alexander Stein <alexander.stein@...tec-electronic.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: coretemp: Support for Intel Atom E6XX CPU (TunnelCreek)?

On Mon, 2011-06-27 at 10:41 -0400, Jean Delvare wrote:
> Hi Alexander,
> 
> On Mon, 27 Jun 2011 12:20:51 +0200, Alexander Stein wrote:
> > I have a patch (for v2.6.39) which adds support for Intel Atom E6XX 
> > (TunnelCreek) to coretemp. It's merely only adding x86_model 0x26.
> 
> You have a patch, great for you. What do you expect if you don't share
> it with us?
> 
> I'm not quite sure what your patch would be doing anyway. Since kernel
> 2.6.35, supported CPU models are detected using the DTS feature flag
> rather than the family and model numbers, so your Atom E6XX should be
> detected just fine.
> 
Maybe it is for Tjmax detection ?

> Note that there was a bug in kernels 2.6.35 to 2.6.39 with regards to
> TjMax guessing, which was fixed by Gunter Roeck with:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=4f5f71a7abe329bdad81ee6a8e4545054a7cc30a
> You'll have to update to kernel version 2.6.39.2 to get this fix.
> 
> Do you happen to know what CPUs model number 0x26 covers? Do you know
> if this model supports MSR_IA32_TEMPERATURE_TARGET or not? The original
> Atom (model 0x1c) did not.
> 
> > But there are models (e.g. E660 and E660T) with different TjMax, namely 90 
> > degrees C and 110 degrees C. But these different model can't be detected by 
> > reading from hardware.
> 
> I would appreciate a patch to Documentation/hwmon/coretemp adding the
> known TjMax for these new Atom models.
> 
> BTW, is it really impossible to identify these models with a different
> TjMax? Don't the strings "E660" and "E660T" appear in the respective
> "model name" entries in /proc/cpuinfo?

I thought about replacing the manual TjMax detection code with code
using the model string to take care of problems like this - essentially
by providing a table with entries { model string, Tjmax } for each CPU
with Tjmax other than 100 degrees C. This way we could get rid of some
of the odd code we have today. Would that make sense ?

Thanks,
Guenter


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