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Re: [PATCH 0/5] PCM mmap (temporary) fixes for non-coherent architect

To: Andreas Mohr <andi@lisas.de>
Subject: Re: [PATCH 0/5] PCM mmap (temporary) fixes for non-coherent architectures
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 13 Jan 2010 10:07:32 +0100
Cc: alsa-devel@alsa-project.org, Ralf Baechle <ralf@linux-mips.org>, Wu Zhangjin <wuzhangjin@gmail.com>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, linux-mips@linux-mips.org, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Kumar Gala <galak@gate.crashing.org>, Becky Bruce <beckyb@kernel.crashing.org>
In-reply-to: <s5haawj7qlv.wl%tiwai@suse.de>
References: <1259248388-20095-1-git-send-email-tiwai@suse.de> <20100101193130.GA21510@rhlx01.hs-esslingen.de> <s5haawj7qlv.wl%tiwai@suse.de>
Sender: linux-mips-bounce@linux-mips.org
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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);

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