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 videodrivers. I suppose they don't work as well, right?DRM driver uses __vmalloc() with PAGE_KERNEL_NOCACHE, but it's onlyfor PPC32 non-coherent.
Takashi
> > Cheers> > Paweł> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c> index 59b29cd..304f9e5 100644> --- a/sound/core/pcm_native.c> +++ b/sound/core/pcm_native.c> @@ -3159,6 +3159,9 @@ static struct vm_operations_struct snd_pcm_vm_ops_data => static int snd_pcm_default_mmap(struct snd_pcm_substream *substream,> struct vm_area_struct *area)> {> +#ifdef pgprot_noncached> + area->vm_page_prot = pgprot_noncached(area->vm_page_prot);> +#endif> area->vm_ops = &snd_pcm_vm_ops_data;> area->vm_private_data = substream;> area->vm_flags |= VM_RESERVED;> diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c> index 7bd5852..c98a4ec 100644> --- a/sound/usb/usbaudio.c> +++ b/sound/usb/usbaudio.c> @@ -714,7 +714,8 @@ static int snd_pcm_alloc_vmalloc_buffer(struct snd_pcm_substream *subs, size_t s> return 0; /* already large enough */> vfree(runtime->dma_area);> }> - runtime->dma_area = vmalloc(size);> + runtime->dma_area = __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM,> + PAGE_KERNEL_NOCACHE);> if (! runtime->dma_area)> return -ENOMEM;> runtime->dma_bytes = size;> _______________________________________________Alsa-devel mailing listAlsa-devel@xxxxxxxxxxxxxxxxxxxx://mailman.alsa-project.org/mailman/listinfo/alsa-devel
