linux-kernel - Re: [PATCH] AMD Thermal Interrupt Support

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Message-ID: <27599.1198897033@turing-police.cc.vt.edu>
Date:	Fri, 28 Dec 2007 21:57:13 -0500
From:	Valdis.Kletnieks@...edu
To:	Andi Kleen <ak@...e.de>
Cc:	Russell Leidich <rml@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] AMD Thermal Interrupt Support

On Sat, 29 Dec 2007 03:34:34 +0100, Andi Kleen said:
> On Saturday 29 December 2007 03:30:17 Valdis.Kletnieks@...edu wrote:
> > On Sat, 29 Dec 2007 03:11:51 +0100, Andi Kleen said:
> > > On Friday 28 December 2007 21:40:28 Russell Leidich wrote:
> > 
> > > +		printk(KERN_CRIT "CPU 0x%x: Thermal monitoring not "
> > > +			"functional.\n", cpu);
> > > 
> > > Why is that KERN_CRIT? Does not seem that critical to me.
> > 
> > If you think you're running on a chipset that *should* support thermal
> > monitoring, and it isn't there in a usable state, that seems pretty critical
> > to me.  If that didn't work, you probably can't trust the "oh, the chip will
> > thermal-limit itself if it gets to 100C or whatever" either.
>
> Thermal shutdown in emergency uses quite different mechanisms (e.g. it goes
> directly through pins to the motherboard); i don't think that code checks for
> that.

Right. My point is that if monitoring *should* be working, and it isn't, then
you don't have a lot of reason to be 100% confident that those pins are working
either.  Unless there's two totally separate temperature sensors - otherwise,
if that sensor goes out, thermal monitoring and the emergency stuff *both*
break.

Of course, if somebody wise on the actual hardware design can definitively
state that even if the thermal sensor the monitoring uses dies, the chipset
will still thermal-throttle correctly, then I'd agree that the message could
go down to KERN_ERR or KERN_WARN.....

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