Re: multi-channel playback regression

[Takashi Iwai <tiwai@suse.de>]

At Thu, 23 Jul 2009 10:39:04 +0200 (CEST),
Jaroslav Kysela wrote:
> 
> On Thu, 23 Jul 2009, Takashi Iwai wrote:
> 
> > At Thu, 23 Jul 2009 10:14:27 +0200 (CEST),
> > Jaroslav Kysela wrote:
> >>
> >> On Thu, 23 Jul 2009, Wu Fengguang wrote:
> >>
> >>>> Is this with the patched (as is on sound git tree) kernel?
> >>>
> >>> Yes, it's unmodified latest git tree.
> >>>
> >>>> What if changing from #if 1 to #if 0?
> >>>
> >>> This makes 8-channel playback work again.
> >>
> >> Can we check if we running under VMWare at runtime?
> >
> > No idea.  But, an option to allow to choose manually might be usefl
> > for other broken hardwares that require a similar fallback like
> > VMware, although this doesn't conflict with the automatic detection
> > of vmware.
> 
> Yes, maybe a sysfs attribute might be useful.

How about the patch below?
This is in sound-unstable tree fix/pcm-hwptr-debug branch.


Takashi

===
>From c1506998c994ed10f637d5dde5f4f54ebc1563f3 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 23 Jul 2009 13:17:50 +0200
Subject: [PATCH] ALSA: pcm - Add sysfs entry to control PCM bogus update filtering

It turned out that the VMware regression fix in the commit
79452f0a28aa5a40522c487b42a5fc423647ad98
introduces another problem for IbexPeak with multi-channels.

This patch adds the new flag and a corresponding sysfs entry to
allow to control this behavior dynamically.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/pcm.h  |    2 ++
 sound/core/pcm.c     |   34 +++++++++++++++++++++++++++++-----
 sound/core/pcm_lib.c |   15 +++++++--------
 3 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 2389352..1cd2f18 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -438,6 +438,8 @@ struct snd_pcm {
 #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
 	struct snd_pcm_oss oss;
 #endif
+	/* misc flags */
+	unsigned int filter_bogus_irq:1;
 };
 
 struct snd_pcm_notify {
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 145931a..15502af 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -942,12 +942,35 @@ static ssize_t show_pcm_class(struct device *dev,
         return snprintf(buf, PAGE_SIZE, "%s\n", str);
 }
 
-static struct device_attribute pcm_attrs =
-	__ATTR(pcm_class, S_IRUGO, show_pcm_class, NULL);
+static ssize_t show_pcm_bogus_irq(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct snd_pcm *pcm = dev_get_drvdata(dev);
+	if (!pcm)
+		return 0;
+	return sprintf(buf, "%d", pcm->filter_bogus_irq);
+}
+
+static ssize_t store_pcm_bogus_irq(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct snd_pcm *pcm = dev_get_drvdata(dev);
+	if (!pcm)
+		return -ENXIO;
+	pcm->filter_bogus_irq = !!simple_strtoul(buf, NULL, 0);
+	return count;
+}
+
+static struct device_attribute pcm_attrs[2] = {
+	__ATTR(pcm_class, S_IRUGO, show_pcm_class, NULL),
+	__ATTR(pcm_bogus_irq, S_IWUSR|S_IRUGO,
+	       show_pcm_bogus_irq, store_pcm_bogus_irq),
+};
 
 static int snd_pcm_dev_register(struct snd_device *device)
 {
-	int cidx, err;
+	int cidx, i, err;
 	struct snd_pcm_substream *substream;
 	struct snd_pcm_notify *notify;
 	char str[16];
@@ -992,8 +1015,9 @@ static int snd_pcm_dev_register(struct snd_device *device)
 			mutex_unlock(&register_mutex);
 			return err;
 		}
-		snd_add_device_sysfs_file(devtype, pcm->card, pcm->device,
-					  &pcm_attrs);
+		for (i = 0; i < ARRAY_SIZE(pcm_attrs); i++)
+			snd_add_device_sysfs_file(devtype, pcm->card,
+						  pcm->device, &pcm_attrs[i]);
 		for (substream = pcm->streams[cidx].substream; substream; substream = substream->next)
 			snd_pcm_timer_init(substream);
 	}
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 065eaf0..1c1ec4c 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -264,19 +264,18 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
 				     "(stream=%i, pos=%ld, intr_ptr=%ld)\n",
 				     substream->stream, (long)pos,
 				     (long)hw_ptr_interrupt);
-#if 1
-			/* simply skipping the hwptr update seems more
-			 * robust in some cases, e.g. on VMware with
-			 * inaccurate timer source
-			 */
-			return 0; /* skip this update */
-#else
+			if (substream->pcm->filter_bogus_irq) {
+				/* simply skipping the hwptr update seems more
+				 * robust in some cases, e.g. on VMware with
+				 * inaccurate timer source
+				 */
+				return 0; /* skip this update */
+			}
 			/* rebase to interrupt position */
 			hw_base = new_hw_ptr = hw_ptr_interrupt;
 			/* align hw_base to buffer_size */
 			hw_base -= hw_base % runtime->buffer_size;
 			delta = 0;
-#endif
 		} else {
 			hw_base += runtime->buffer_size;
 			if (hw_base >= runtime->boundary)
-- 
1.6.3.3