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Subject: Re: Voyager subarchitecture for 2.5.46
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "J.E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: john stultz <johnstul@us.ibm.com>, Linus Torvalds <torvalds@transmeta.com>,
       lkml <linux-kernel@vger.kernel.org>
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On Wed, 2002-11-06 at 15:03, J.E.J. Bottomley wrote:
> There are certain architectures (voyager is the only one currently supported, 
> but I suspect the Numa machines will have this too) where the TSC cannot be 
> used for cross CPU timings because the processors are driven by separate 
> clocks and may even have different clock speeds.

IBM Summit is indeed another one. 

> What I need is an option simply not to compile in the TSC code and use the PIT 
> instead.  What I'm trying to do with the TSC and PIT options is give three 
> choices:
> 
> 1. Don't use TSC (don't compile TSC code): X86_TSC=n, X86_PIT=y
> 
> 2. May use TSC but check first (blacklist, notsc kernel option).  X86_TSC=y, 
> X86_PIT=y
> 
> 3. TSC is always OK so don't need PIT.  X86_TSC=y, X86_PIT=n

[Plus we need X86_CYCLONE and we may need X86_SOMETHING else for some
pending stuff]

> We probably need to make the notsc and dodgy tsc check contingent on X86_PIT 
> (or a config option that says we have some other timer mechanism compiled in). 
>  Really, the options should probably be handled in timer.c.

The dodgy_tsc check is now obsolete. The known cases are handled with
workarounds and CS5510/20 can now use the TSC

> Do we have an option for a deferred panic that will trip just after we init 
> the console and clean out the printk buffer?

Point to timer_none, check that later on in the boot


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