[alsa-devel] [PATCH 0/5] PCM mmap (temporary) fixes for non-coherent architectures

[Takashi Iwai]

At Tue, 12 Jan 2010 08:02:36 +0100,
I wrote:
> 
> At Fri, 1 Jan 2010 20:31:30 +0100,
> Andreas Mohr wrote:
> > 
> > Hi,
> > 
> > I've tried this patch set (with the typo-corrected part 4) on my ASUS
> > WL-500gP v2 MIPSEL via a backport to 2.6.31.9, but all I get is a
> > small blip of the sound I wanted to play, and then the system is fubar
> > (I believe just the same thing as what happened without having this patch
> > applied).
> 
> As I mentioned in the previous followup, if your device is a
> USB-audio, the patch doesn't help because it's for devices with
> buffers using dma_alloc_coherent().  For USB-audio, it uses vmalloc
> for an intermediate buffer.  Maybe this should be changed to dma_*()
> stuff for such architectures.

A quick patch below (totally untested!) might do that.
It's passing the device struct blindly, so not sure whether this would
actually work for all dma_alloc_coherent().


Takashi

---
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 9edef46..6c82026 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -734,7 +734,7 @@ static void snd_complete_sync_urb(struct urb *urb)
 	}
 }
 
-
+#ifdef USBAUDIO_VMALLOC_BUFFER
 /* get the physical page pointer at the given offset */
 static struct page *snd_pcm_get_vmalloc_page(struct snd_pcm_substream *subs,
 					     unsigned long offset)
@@ -769,6 +769,24 @@ static int snd_pcm_free_vmalloc_buffer(struct snd_pcm_substream *subs)
 	return 0;
 }
 
+#define preallocate_buffer(chip, pcm, stream) /* NOP */
+
+#else
+#define snd_pcm_get_vmalloc_page	NULL
+#define snd_pcm_alloc_vmalloc_buffer	snd_pcm_lib_malloc_pages
+#define snd_pcm_free_vmalloc_buffer	snd_pcm_lib_free_pages
+
+static int preallocate_buffer(struct snd_usb_audio *chip, struct snd_pcm *pcm,
+			      int stream)
+{
+	struct snd_pcm_substream *subs = pcm->streams[stream].substream;
+	if (!subs)
+		return 0;
+	return snd_pcm_lib_preallocate_pages(subs, SNDRV_DMA_TYPE_DEV,
+					     chip->card->dev,
+					     1024 * 64, 1024 * 1024);
+}
+#endif
 
 /*
  * unlink active urbs.
@@ -2328,6 +2346,7 @@ static int add_audio_endpoint(struct snd_usb_audio *chip, int stream, struct aud
 		err = snd_pcm_new_stream(as->pcm, stream, 1);
 		if (err < 0)
 			return err;
+		preallocate_buffer(chip, as->pcm, stream);
 		init_substream(as, stream, fp);
 		return 0;
 	}
@@ -2356,6 +2375,7 @@ static int add_audio_endpoint(struct snd_usb_audio *chip, int stream, struct aud
 	else
 		strcpy(pcm->name, "USB Audio");
 
+	preallocate_buffer(chip, pcm, stream);
 	init_substream(as, stream, fp);
 
 	list_add(&as->list, &chip->pcm_list);