Re: [PATCH] mips: Add dma_mmap_coherent()

[Takashi Iwai <tiwai@suse.de>]

At Fri, 22 Aug 2008 16:36:22 +0200,
Thomas Bogendoerfer wrote:
> 
> 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.

Hmm, not so easy...

> I'd start with just
> 
> prot |= _CACHE_UNCACHED
> 
> and if some MIPS system needs more specific treatment, we just add
> that later.

OK, then it's essentially pgprog_noncached() as in my second patch.


Thanks!

Takashi