openwrt/target/linux/s3c24xx/patches-2.6.24/1205-workaround-s3c24xx-i2s-stop-live-stream-stall-on-res.patch

From edd4b9c7128495063fb529282ebbf165a20f7a23 Mon Sep 17 00:00:00 2001
From: Andy Green <andy@openmoko.com>
Date: Wed, 2 Jul 2008 22:42:56 +0100
Subject: [PATCH] workaround-s3c24xx-i2s-stop-live-stream-stall-on-resume.patch
 Reported-by: Graeme Gregory <graeme@openmoko.org>
 Basically-solved-by: Graeme Gregory <graeme@openmoko.org>

Graeme found a while back that on resume, IISCON register in
s3c2442 does not show LRCK toggling in LRINDEX bit any more,
causing s3c24xx_snd_lrsync() to timeout and return an error,
aborting restart of any live stream that was playing at
suspend.

I confirmed it was true, meddled around for a bit looking
for some magic to restart LRCK or at least the reporting of
it, and in the end worked around it using the method noted
by Graeme: just ignore LRCK sync if it timed out.  The worst
that could happen would be L and R swap for the duration of
stream that was suspended into but probably not even that.

Signed-off-by: Andy Green <andy@openmoko.com>
---
 sound/soc/s3c24xx/s3c24xx-i2s.c |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/sound/soc/s3c24xx/s3c24xx-i2s.c b/sound/soc/s3c24xx/s3c24xx-i2s.c
index 7b6cca7..4ec37ef 100644
--- a/sound/soc/s3c24xx/s3c24xx-i2s.c
+++ b/sound/soc/s3c24xx/s3c24xx-i2s.c
@@ -180,7 +180,7 @@ static void s3c24xx_snd_rxctrl(int on)
 static int s3c24xx_snd_lrsync(void)
 {
 	u32 iiscon;
-	int timeout = 50; /* 5ms */
+	int timeout = 5; /* 500us, 125 should be enough at 8kHz */
 
 	DBG("Entered %s\n", __FUNCTION__);
 
@@ -285,11 +285,14 @@ static int s3c24xx_i2s_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		if (!s3c24xx_snd_is_clkmaster()) {
-			ret = s3c24xx_snd_lrsync();
-			if (ret)
-				goto exit_err;
-		}
+		if (!s3c24xx_snd_is_clkmaster())
+			/* we ignore the return code, if it sync'd then fine,
+			 * if it didn't sync, which happens after resume the
+			 * first time when there was a live stream at suspend,
+			 * just let it timeout, the stream picks up OK after
+			 * that and LRCK is evidently working again.
+			 */
+			s3c24xx_snd_lrsync();
 
 		if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
 			s3c24xx_snd_rxctrl(1);
-- 
1.5.6.5