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SubjectRe: MediaGX/GeodeGX1 requires X86_OOSTORE.
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From: lsorense@csclub.uwaterloo.ca (Lennart Sorensen)
Subject: Re: MediaGX/GeodeGX1 requires X86_OOSTORE.
Date: Tue, 20 Feb 2007 09:48:23 -0500

Hiroshi Miura posted `Geode out-of-order store enables' patch in Jun, 2003.
There is http://lkml.org/lkml/2003/6/5/57 .
OOSTORE was enabled at this point in time. It seems to have disappeared somewhere.

BTW, I use MediaGX with kernel 2.6.20(and 2.6.20.3) and suspend2. When I resume
the PC and use the PC Card modem, PC is hungup. However, PC isn't hung up when
I apply a WBINVD patch.
I can't understand it whether there is problem in resume of suspend2 or MediaGX
or both. Many drivers lack support for resume on my PC.

> On Tue, Feb 20, 2007 at 08:34:13PM +0900, takada wrote:
> > I posted with 2.6.20 + enabled X86_OOSTORE.
> > The clflush sze line is in /proc/cpuinfo. but clfush is not in flags line.
> >
> > BTW, can we use WBINVD instruction? I tested compile only.
> > Do you know a method to change dynamically without #ifdef when it works
> > with MediaGX/GeodeGX.
> >
> > diff -Narup a/include/asm-i386/io.h b/include/asm-i386/io.h
> > --- a/include/asm-i386/io.h 2007-02-20 16:23:25.000000000 +0900
> > +++ b/include/asm-i386/io.h 2007-02-20 17:07:14.000000000 +0900
> > @@ -232,7 +232,19 @@ static inline void memcpy_toio(volatile
> > * 2. Accidentally out of order processors (PPro errata #51)
> > */
> >
> > -#if defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE)
> > +#ifdef CONFIG_MGEODEGX1
> > +
> > +static inline void dma_flush_cache(void)
> > +{
> > + __asm__ __volatile__ ("wbinvd": : :"memory");
> > +}
> > +
> > +#define dma_cache_inv(_start,_size) dma_flush_cache()
> > +#define dma_cache_wback(_start,_size) dma_flush_cache()
> > +#define dma_cache_wback_inv(_start,_size) dma_flush_cache()
> > +#define flush_write_buffers()
> > +
> > +#elif defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE)
> >
> > static inline void flush_write_buffers(void)
> > {
> > -
>
> Well it is starting to look like it isn't a caching issue, but more
> likely an issue of which order writes are performed in. I think the MAC
> might be seeing the ownership bit change before the rest of the
> descriptor, which shouldn't happen. With X86_OOSTORE, wmb() is called
> between setting the fields in the descriptor and setting the ownership
> bit to the MAC. I still have to investigate a bit more to find out for
> sure, but that could certainly explain why X86_OOSTORE makes the problem
> become much less frequent. It doesn't completely elliminate it though.
> Of course maybe there are two different problems with the same symptoms.
>
> --
> Len Sorensen
> -
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