linux-kernel - Re: [PATCH 1/1] i386: Geode's TSC is not neccessary to mark tu unstable

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Date:	Thu, 19 Jul 2007 03:17:12 -0400
From:	Andres Salomon <dilinger@...ued.net>
To:	Juergen Beisert <juergen127@...uzholzen.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	TAKADA Yoshihito <takada@....nifty.com>,
	linux-kernel@...r.kernel.org,
	Jordan Crouse <jordan.crouse@....com>,
	Andres Salomon <dilinger@...ian.org>, Andi Kleen <ak@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 1/1] i386: Geode's TSC is not neccessary to mark tu
 unstable

On Thu, 19 Jul 2007 08:49:05 +0200
Juergen Beisert <juergen127@...uzholzen.de> wrote:

> On Thursday 19 July 2007 03:02, Andrew Morton wrote:
> > On Sun, 15 Jul 2007 21:06:27 +0200
> >
> > Juergen Beisert <juergen127@...uzholzen.de> wrote:
> > > Replace NSC/Cyrix specific chipset access macros by inlined functions.
> > > With the macros a line like this fails (and does nothing):
> > > 	setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);
> > > With inlined functions this line will work as expected.
> >
> > I don't get it.  Why would the macros behave differently from inlined
> > functions?
> 
> X86 magic. The access order is important. The first access must always be the 
> offset at 0x22. This access enables the next access to 0x23 (data). If you do 
> it in wrong order, it fails. With the macros you get something like 0x22, 
> 0x22, 0x23, 0x23. With the inline functions 0x22,0x23,0x22,0x23.
> 
> Juergen

Wow, that's a really cool bug; nice work!  Don't forget to update
arch/i386/kernel/cpu/mtrr/state.c, though; it uses setCx86() as well.  It needs
to include processor-cyrix.h.


Acked-by: Andres Salomon <dilinger@...ian.org>

-- 
Andres Salomon <dilinger@...ued.net>
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