On Sat, Jan 16, 2010 at 11:05:12AM +0100, Takashi Iwai wrote: > At Fri, 15 Jan 2010 09:04:17 +0900, > Paul Mundt wrote: > > > > On Fri, Sep 26, 2008 at 12:04:23PM +0200, Takashi Iwai wrote: > > > At Thu, 25 Sep 2008 15:55:53 +0100, > > > Pawel MOLL wrote: > > > > > > > > > One thing we can try is a patch like below. But, I'm not sure whether > > > > > this is correct over all architectures, too. At best, a generic API > > > > > would be helpful for such a thing... > > > > > + area->vm_page_prot = pgprot_noncached(area->vm_page_prot); > > > > > > > > Well, it's not enough, because the kernel mapping of buffer is still > > > > cached... A hack below does the job, but it is not nice as well... > > > > > > Yeah, that's not sexy, but maybe the only working case right now > > > (better with arch-specific ifdefs). > > > > > > IIRC, a similar buffer handling (via vmalloc) is used in video > > > drivers. I suppose they don't work as well, right? > > > DRM driver uses __vmalloc() with PAGE_KERNEL_NOCACHE, but it's only > > > for PPC32 non-coherent. > > > > > To come back to this issue, we don't appear to have made any headway on > > the vmalloc front, but pgprot_noncached() is now a standard interface > > provided by all architectures, so the ifdef is no longer needed in the > > snd_pcm_default_mmap() path. > > Thanks for heading up about this. > > It seems, however, that pgprot_noncached() is still dangerous to apply > unconditionally, according to MIPS guys. Some MIPS platforms may freeze > when this is set to invalid pages. > > So, this should be applied still in an arch-dependent manner... > Oh well. > Then it is something they will have to fix on their own. It's used by the generic VM code for VMA writenotify (see mm/mmap.c). _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
