linux-kernel - Re: sound skipping regression introduced in 2.6.30-rc8

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Date:	Fri, 12 Jun 2009 03:52:48 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Sven Köhler <sven.koehler@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: sound skipping regression introduced in 2.6.30-rc8

At Thu, 11 Jun 2009 23:38:17 +0200,
Sven Köhler wrote:
> 
> >>>> Can somebody point out, how I can set this xrun_debug thing or can
> >>>> somebody provide a patch that reverts the change?
> >>> Did you read my reply to David?
> >> I will try, what is described there and I will report back if I get any
> >> debug output.
> > 
> > Thanks, that'll be be helpful.
> 
> Below is the output. Note, that audacious 2.x was not only skipping a
> little bit. In fact, the clock that was showing the time of audio played
> was running twice as fast or even 4 times as fast. The sound was played
> at the right samplerate but in fast it seems, that much of the audio
> data was skipped and I only heard a series of short fragments of what
> should have been the song I'm listening to.
> 
> 
> PCM: hw_ptr skipping! (pos=4096, delta=7169, period=1024, jdelta=0/149)

OK, it must be the same problem indeed as David and Bartlomiej see.

Although Bartlomiej wrote that reverting the commit below didn't help,
I still suspect it comes from there.
     commit da2436a23c038055b1da6fe30b6ea2886b1e07b0
     Author: Jaroslav Kysela <perex@...ex.cz>
     Date:   Mon Apr 13 21:31:25 2009 +0200
     [ALSA] intel8x0: do not use zero value from PICB register

The below is a revised patch to fix the possible regression from this.
Could you guys give it a try, or check reverting the above?


thanks,

Takashi

---
diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c
index 173bebf..2446ed6 100644
--- a/sound/pci/intel8x0.c
+++ b/sound/pci/intel8x0.c
@@ -1077,15 +1077,18 @@ static snd_pcm_uframes_t snd_intel8x0_pcm_pointer(struct snd_pcm_substream *subs
 		ptr1 <<= ichdev->pos_shift;
 		ptr = ichdev->fragsize1 - ptr1;
 		ptr += position;
-		ichdev->last_pos = ptr;
-		ichdev->last_pos_jiffies = jiffies;
 	} else {
 		ptr1 = jiffies - ichdev->last_pos_jiffies;
 		if (ptr1)
 			ptr1 -= 1;
 		ptr = ichdev->last_pos + ptr1 * ichdev->jiffy_to_bytes;
 		ptr %= ichdev->size;
+		if (ptr < position ||
+		    ptr > position + substream->runtime->period_size)
+			ptr = position;
 	}
+	ichdev->last_pos = ptr;
+	ichdev->last_pos_jiffies = jiffies;
 	spin_unlock(&chip->reg_lock);
 	if (ptr >= ichdev->size)
 		return 0;
--
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