On Fri, 2011-03-25 at 09:01 +0100, Takashi Iwai wrote: > > In fact, cache coherent architectures often don't support mapping memory > > uncached -at-all- so something like snd_pcm_lib_mmap_noncached() > > shouldn't exist, or at least be under arch control. There's no case > > where it's "always safe". There will almost always be a cache alias in > > the linear mapping unless special arch specific sauce has been applied. > > I see. I'll take your removal patch. > It should be applied to stable kernel, too, right? I suppose so :-) > > Now, there's another problem on top of that, which is that > > snd_pcm_default_mmap() will not work properly the "other way around" on > > powerpc, where the mapping -needs- to be uncached bcs you are running on > > a non cache coherent embedded CPU and trying to mmap DMA memory, but > > that's something that needs fixing inside powerpc by properly defining > > dma_mmap_coherent() & ARCH_HAS_DMA_MMAP_COHERENT (I thought we had added > > it a while back but it's not upstream, patch must have got lost). > > Mea culpa. I moved to a different team and have had little time for > the upstream development since then... That's ok, I did a new one, which you have noticed already anyways :-) > > We > > must also make sure we don't go down that path for vmalloc memory > > though. > > Yes. I haven't actually checked, but I assume that the test substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV In snd_pcm_default_mmap() takes care of that, please correct me if I'm wrong in which case we'll need something else there. > Your patch looks good. Thanks for taking care of this! Are you taking care of sending it upstream ? Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
