linux-kernel - Re: [lm-sensors] [PATCH] hwmon: Add driver for VIA CPU core temperature

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Date:	Fri, 12 Jun 2009 08:09:05 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Harald Welte <HaraldWelte@...tech.com>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Tomaz Mertelj <tomaz.mertelj@...st.arnes.si>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] [PATCH] hwmon: Add driver for VIA CPU core temperature

On Fri June 12 2009, Harald Welte wrote:
> On Fri, Jun 12, 2009 at 06:46:45AM -0500, Michael S. Zick wrote:
> > > Temperature values are supposed to be expressed in millidegrees C, not
> > > degrees C as it seems to be doing (although 25 degrees C seems pretty
> > > low for a CPU temperature?) The drivers needs to multiply values by
> > > 1000 before exporting them to sysfs. Then "sensors" will report the
> > > correct temperature value.
> > > 
> > 
> > Ah, 25 degrees C is room temperature - real hard for the junction temperature
> > to be 25 degrees C with power applied; lacking an infinitely perfect heatsink.
> > 
> > Look for an "off by one" error in shifting or masking the value.
> 
> there is no shifting and the masking is 0xffffffff :)
> 
> it might be that the BIOS is doing something wrong when programming the
> calibration MSR's at early botoup.  I would need the contents of MSR 
> 0x1160 ... 0x116C as well as 0x1152 and 0x1153 to be able to determine that.
> 

I was commenting on someone else's observation - -
Will build with your patch and poke at it a bit.

I should be able to read those registers from /dev/cpu/0/msr, correct?
Or is there a "safe" mask in the msr driver that prevents reading random
MSR registers?

Mike
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