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Date:	Fri, 22 Aug 2008 16:36:22 +0200
To:	Takashi Iwai <tiwai@suse.de>
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	James Bottomley <James.Bottomley@HansenPartnership.com>,
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Subject: Re: [PATCH] mips: Add dma_mmap_coherent()
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From:	tsbogend@alpha.franken.de (Thomas Bogendoerfer)
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On Fri, Aug 22, 2008 at 12:23:48PM +0200, Takashi Iwai wrote:
> 	unsigned long prot = pgprot_val(_prot) & ~_CACHE_MASK;
> #ifdef CONFIG_SGI_IP32
> #ifdef CONFIG_CPU_R10000
> 	prot = prot | _CACHE_UNCACHED_ACCELERATED;
> #else
> 	prot = prot | _CACHE_CACHABLE_NO_WA;
> #endif
> #else
> 	prot = prot | _CACHE_UNCACHED;
> #endif
> 	return __pgprot(prot);

this won't work for recording channels on IP32, because the write trough
mapping will hide updates done via DMA.

I'd start with just

prot |= _CACHE_UNCACHED

and if some MIPS system needs more specific treatment, we just add
that later.

Thomas.

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