On Fri, 2011-03-25 at 11:12 +0100, Takashi Iwai wrote: > At Fri, 25 Mar 2011 20:15:33 +1100, > Benjamin Herrenschmidt wrote: > > > > > > 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. > > Well, in the case of usb-audio, it's not handled via > dma_mmap_coherent(), as the page isn't allocated via > dma_alloc_coherent() but vmalloc(). Right, I just wanted to make sure I was right to assume that a page allocated by vmalloc() was going to fail the above test in snd_pcm_default_mmap() and thus -not- get into dma_mmap_coherent()... just double checking as I'm not totally familiar with the intricacies of the pcm code :-) > The bad commit was to overcome some problems on SH platform, IIRC, > when it's used with dmix -- i.e. concurrent accesses on the mmapped > buffer from multiple processes. But, this looks obviously like a > wrong approach. Is this a vivt architecture ? Maybe enforcing some restrictions on the virtual addresses so they hit the same cache congruence classes ? > Actually, the buffer allocated there in usb-audio is an intermediate > buffer, that isn't directly transferred to hardware. We may need a > bit more consideration what is the best way to solve that issue (if > it's still really present). Right. I wouldn't expect vmalloc stuff to hit HW in most cases anyways, though I do wonder why you don't pass the buffer directly to the HCD and avoid that intermediate step but that's a completely different question :-) > > > Your patch looks good. Thanks for taking care of this! > > > > Are you taking care of sending it upstream ? > > I'll apply the patch to remove vmalloc pgprot thingy surely to sound > tree and include in the next pull request. > > Others should be sent through arch maintainers (PPC and ARM), right? Well, I am ppc maintainer so that's sorted :-) I've CCed Russell for the other, it's up to him, I have no specific dependency there, it's just an easy cleanup I stumbled upon. Cheers, Ben. > > thanks, > > Takashi > -- > 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 -- 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
