linux-kernel - Re: System clock runs too fast after 2.6.27 -> 2.6.28.1 upgrade

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Message-ID: <1f1b08da0901231736u46d8981ckc4b89ac66d7d8a5e@mail.gmail.com>
Date:	Fri, 23 Jan 2009 17:36:30 -0800
From:	john stultz <johnstul@...ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Miklos Vajna <vmiklos@...galware.org>,
	Florian Fainelli <florian.fainelli@...ecomint.eu>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Gabriel C <nix.or.die@...glemail.com>,
	CSÉCSY László <boobaa@...galware.org>,
	r.schwebel@...gutronix.de, sven@...gus.net
Subject: Re: System clock runs too fast after 2.6.27 -> 2.6.28.1 upgrade

On Fri, Jan 23, 2009 at 3:04 AM, Ingo Molnar <mingo@...e.hu> wrote:
> * john stultz <johnstul@...ibm.com> wrote:
>> I'd think this would ideally be more of a subarch in the config
>> selection like the AMD Elan is, so folks know it really is not just a
>> extra-support feature and in fact limits what hardware you can use the
>> resulting kernel on.
>
> a better solution is that if RDC is set [it is unset by default] we should
> turn PIT_TICK_RATE into a variable, defaulting it to 1193182. If a real
> RDC or ELAN system is running, that variable is changed during early
> bootup, in the init functions for those platforms.

Took a quick look at this, and I don't see any detection code for
either RDC. The X86_ELAN config also has no conditionals, but maybe
the elan cpufreq code can help here.

Florian: Is there any way we can check very early (ie: in setup_arch)
for an RDC box?

Robert Schwebel, Sven Geggus: Either of you still maintaining the ELAN
code?  Will the following from elanfreq_cpu_init catch all ELAN chips?

        if ((c->x86_vendor != X86_VENDOR_AMD) ||
            (c->x86 != 4) || (c->x86_model != 10))


thanks
-john
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