linux-kernel - Re: [lm-sensors] [PATCH] hwmon: (coretemp) Fix TjMax for Atom N450/D410/D510 CPUs

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Message-ID: <20100118065821.GA19008@ywang-moblin2.bj.intel.com>
Date:	Mon, 18 Jan 2010 14:58:21 +0800
From:	Yong Wang <yong.y.wang@...ux.intel.com>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Robert Hancock <hancockrwd@...il.com>,
	Yuhong Bao <yuhongbao_386@...mail.com>,
	yong.y.wang@...ux.intel.com, linux-kernel@...r.kernel.org,
	huaxu.wan@...el.com, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] [PATCH] hwmon: (coretemp) Fix TjMax for Atom
	N450/D410/D510 CPUs

On Sun, Jan 17, 2010 at 09:05:36PM +0100, Jean Delvare wrote:
> On Sun, 17 Jan 2010 13:29:06 -0600, Robert Hancock wrote:
> > On 01/17/2010 09:15 AM, Jean Delvare wrote:
> > > On Fri, 15 Jan 2010 18:02:27 -0800, Yuhong Bao wrote:
> > >>
> > >>> No matter what chipset or gfx you use with the new Atom chip, the
> > >>> integrated memory controller (IMC) will always be used. This patch
> > >>> checks the presence of that IMC. Hope this clarifies.
> > >> To be more precise, Pine Trail Atoms integrate the entire northbridge, including the integrated graphics and the memory controller into the CPU, and there is a DMI connection to the southbridge, which is the Intel NM10, that is NOT integrated.

This is correct.

> > >
> > > What prevents another vendor from selling a compatible south bridge
> > > then?
> > 
> > Nothing (other than licensing for the DMI bus, see NVIDIA and the 
> > problems this creates for their ION chipset). I'm assuming this patch is 
> > checking for the host bridge device though, that is integrated into the 
> > CPU and would always be present.
> 
> That's where I am confused. The patch checks for the presence of the
> Intel NM10, which, reading its description looks much like a south
> bridge and not a memory controller (north bridge). So I think the patch
> is wrong (or at least incomplete).
> 

Sorry, I made a mistake in the patch description. The new Atom CPU is
coupled with integrated gfx and memory controller in one package. NM10
chipset is another chip. This patch does check the presence of the
integrated memory controller, i.e. 00:00.0 Host bridge device, which
will always be present no matter whether NM10 chipset is used or not.

> Anyway, how difficult would it be to set TjMax based on the CPUID? I
> presume that the Intel Atom 400 and 500 series have their own CPUID
> value, haven't they? This would seem even easier that checking for a
> PCI device.
> 

CPUID value (family and model number) remains the same for all Atom CPUs
thus far. That is why we check the new Atom CPU this way.

Thanks
-Yong

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