Re: [Alsa-devel] RFC: dma_mmap_coherent() for powerpc/ppc architecture and ALSA?

[Takashi Iwai <tiwai@suse.de>]

At Mon, 12 Jun 2006 16:42:54 +0200,
Gerhard Pircher wrote:
> 
> > > But as far as I understand this would require a rewrite of all the
> > > ALSA drivers (or at least a rewrite of the ALSA's DMA helper
> > > functions).
> > 
> > Yes.  The change of ALSA side has been also on my tree.  But it was
> > still pending since I'm not satisfied with the design yet.
> > If you're interested in it, let me know.  I'll post the patch.
> 
> Yes, please! Then I can test, if the dma_mmap_coherent() patch works on
> my non cache coherent powerpc machine.

For using dma_mmap_coherent(), the patch below should suffice.
(Also you need to enable HAVE_DMA_MMAP_COHERENT there not only for
 ARM.)

> Do you think the DMA Layer/ALSA patches will go upstream in one of
> the next ALSA/Linux kernel versions? 

Definitely no 2.6.18 material yet.


Takashi


diff -r 08577d0b45ef sound/core/pcm_native.c
--- a/sound/core/pcm_native.c	Tue Jun 13 12:01:14 2006 +0200
+++ b/sound/core/pcm_native.c	Wed Jun 14 16:40:32 2006 +0200
@@ -3123,6 +3123,10 @@ static int snd_pcm_mmap_control(struct s
 }
 #endif /* coherent mmap */
 
+#if defined(CONFIG_ARM)
+#define HAVE_DMA_MMAP_COHERENT
+#endif
+
 /*
  * nopage callback for mmapping a RAM page
  */
@@ -3166,6 +3170,14 @@ static struct vm_operations_struct snd_p
 	.nopage =	snd_pcm_mmap_data_nopage,
 };
 
+#ifdef HAVE_DMA_MMAP_COHERENT
+static struct vm_operations_struct snd_pcm_vm_ops_data_one_map =
+{
+	.open =		snd_pcm_mmap_data_open,
+	.close =	snd_pcm_mmap_data_close,
+};
+#endif
+
 /*
  * mmap the DMA buffer on RAM
  */
@@ -3175,6 +3187,16 @@ static int snd_pcm_default_mmap(struct s
 	area->vm_ops = &snd_pcm_vm_ops_data;
 	area->vm_private_data = substream;
 	area->vm_flags |= VM_RESERVED;
+#ifdef HAVE_DMA_MMAP_COHERENT
+	if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV) {
+		area->vm_ops = &snd_pcm_vm_ops_data_one_map;
+		if (dma_mmap_coherent(substream->dma_buffer.dev.dev, area,
+				      substream->runtime->dma_area,
+				      substream->runtime->dma_addr,
+				      area->vm_end - area->vm_start))
+			return -EAGAIN;
+	}
+#endif
 	atomic_inc(&substream->mmap_count);
 	return 0;
 }