ALSA: pcm - fix page conversion on non-coherent PPC arch

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().

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -3069,6 +3069,16 @@ snd_pcm_default_page_ops(struct snd_pcm_substream *substream, unsigned long ofs)
 #if defined(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT)
 	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(addr >> PAGE_SHIFT);
+	}
 #endif
 	return virt_to_page(vaddr);
 }