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Re: [PATCH] IP28 support

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH] IP28 support
From: tsbogend@alpha.franken.de (Thomas Bogendoerfer)
Date: Thu, 29 Nov 2007 10:58:44 +0100
Cc: linux-mips@linux-mips.org
In-reply-to: <20071128143459.GA22943@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20071126224004.D885AC2B26@solo.franken.de> <20071128143459.GA22943@linux-mips.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.13 (2006-08-11)
On Wed, Nov 28, 2007 at 02:34:59PM +0000, Ralf Baechle wrote:
> > diff --git a/include/asm-mips/dma.h b/include/asm-mips/dma.h
> > index 833437d..80caf6b 100644
> > --- a/include/asm-mips/dma.h
> > +++ b/include/asm-mips/dma.h
> > @@ -88,6 +88,9 @@
> >  /* Horrible hack to have a correct DMA window on IP22 */
> >  #include <asm/sgi/mc.h>
> >  #define MAX_DMA_ADDRESS            (PAGE_OFFSET + SGIMC_SEG0_BADDR + 
> > 0x01000000)
> > +#elif defined(CONFIG_SGI_IP28)
> > +#include <asm/sgi/mc.h>
> > +#define MAX_DMA_ADDRESS            (PAGE_OFFSET + SGIMC_SEG1_BADDR + 
> > 0x01000000)
> >  #else
> >  #define MAX_DMA_ADDRESS            (PAGE_OFFSET + 0x01000000)
> >  #endif
> 
> I've always been wondering if the even the IP22 segment was correct at
> all.  Afair nobody ever had (E)ISA DMA working on Indigo 2 so that code
> is a shot into the dark.  Of course for now it's the sanest thing to
> assume that IP28 is the same as the "classic" Indigo 2.

I've changed that in the updated IP28 patch. I don't see a way to
support ISA busmaster devices, because they will generate a physical
address between 0 and 0x1000000, which will only hit the 512 KB
mirrored RAM. Anything which uses ISA slave DMA is able to address
the full 32bit address space.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessary a
good idea.                                                [ RFC1925, 2.3 ]

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