Re: [PATCH 4/5] ALSA: pcm - fix page conversion on non-coherent PPC arch

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Thu, 2009-11-26 at 16:13 +0100, Takashi Iwai wrote:
> The non-cohernet PPC arch doesn't give the correct address by a simple
> virt_to_page() for pages allocated via dma_alloc_coherent().
> This patch adds a hack to fix the conversion similarly like MIPS.
> 
> Note that this doesn't fix perfectly: the pages should be marked with
> proper pgprot value.  This will be done in a future implementation like
> the conversion to dma_mmap_coherent().
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

This will not work with swiotlb, but then, I don't think we have -yet-
to deal with a platform that does both swiotlb and isn't DMA
coherent :-)

Of course, the conversion to dma_mmap_coherent will makes things better
though we really will want to push that function into the dma ops.

So it's hackish but for now its an

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Cheers,
Ben.

> ---
>  sound/core/pcm_native.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index e48c5f6..76eb763 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -3070,6 +3070,16 @@ snd_pcm_default_page_ops(struct snd_pcm_substream *substream, unsigned long ofs)
>  	if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
>  		return virt_to_page(CAC_ADDR(vaddr));
>  #endif
> +#if defined(CONFIG_PPC32) && defined(CONFIG_NOT_COHERENT_CACHE)
> +	if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV) {
> +		dma_addr_t addr = substream->runtime->dma_addr + ofs;
> +		addr -= get_dma_offset(substream->dma_buffer.dev.dev);
> +		/* assume dma_handle set via pfn_to_phys() in
> +		 * mm/dma-noncoherent.c
> +		 */
> +		return pfn_to_page(dma_handle >> PAGE_SHIFT);
> +	}
> +#endif
>  	return virt_to_page(vaddr);
>  }
>