Messages in this thread |  | | Date | Tue, 01 Jan 2002 13:49:34 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH][RFC] AMD Elan patch |
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Robert Schwebel wrote:
> diff -urN -X kernel-patches/dontdiff linux-2.4.17/arch/i386/boot/setup.S linux-2.4.17-rs/arch/i386/boot/setup.S > --- linux-2.4.17/arch/i386/boot/setup.S Fri Nov 9 22:58:02 2001 > +++ linux-2.4.17-rs/arch/i386/boot/setup.S Mon Dec 31 17:20:17 2001 > @@ -42,6 +42,9 @@ > * if CX/DX have been changed in the e801 call and if so use AX/BX . > * Michael Miller, April 2001 <michaelm@mjmm.org> > * > + * New A20 code ported from SYSLINUX by H. Peter Anvin. AMD Elan bugfixes > + * by Robert Schwebel, December 2001 <robert@schwebel.de> > + * > */ > > #include <linux/config.h> > @@ -646,7 +649,14 @@ > # > # Enable A20. This is at the very best an annoying procedure. > # A20 code ported from SYSLINUX 1.52-1.63 by H. Peter Anvin. > +# AMD Elan bug fix by Robert Schwebel. > # > + > +#if defined(CONFIG_MELAN) > + inb $0xee, %al # reading 0xee enables A20 > + jmp a20_done > +#endif > + >
Do you have documentation which verifies that A20 is enabled by the time the IN instruction returns? If not, you probably don't want to jump to a20_done, but rather fall into a loop like the following:
#if defined(CONFIG_MELAN) inb $0xee, %al a20_elan_wait: call a20_test jz a20_elan_wait jmp a20_done #endif
Furthermore, I would still like to argue that this does not belong into "processor type and features", because all of these are *chipset* issues; in fact, in this particular case you're more than anything working around a BIOS bug (not having INT 15h AX=2401h do the right thing).
I'm also very uncomfortable with putting this where you do; I think it should be put before a20_kbc instead. If the BIOS is implemented correctly, it should be used.
-hpa
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