From 988cc17552606be67a956cf8cd6ff504cfc5d643 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 26 Apr 2021 08:33:49 +0200
Subject: [PATCH] ALSA: usb-audio: Fix implicit sync clearance at stopping stream
Git-commit: 988cc17552606be67a956cf8cd6ff504cfc5d643
Patch-mainline: v5.13-rc1
References: git-fixes

The recent endpoint management change for implicit feedback mode added
a clearance of ep->sync_sink (formerly ep->sync_slave) pointer at
snd_usb_endpoint_stop() to assure no leftover for the feedback from
the already stopped capture stream.  This turned out to cause a
regression, however, when full-duplex streams were running and only a
capture was stopped.  Because of the above clearance of ep->sync_sink
pointer, no more feedback is done, hence the playback will stall.

This patch fixes the ep->sync_sink clearance to be done only after all
endpoints are released, for addressing the regression.

Reported-and-tested-by: Lucas Endres <jaffa225man@gmail.com>
Fixes: bf6313a0ff76 ("ALSA: usb-audio: Refactor endpoint management")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210426063349.18601-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/endpoint.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index f4c3d2b38abb..014c43862826 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -1443,11 +1443,11 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
 	if (snd_BUG_ON(!atomic_read(&ep->running)))
 		return;
 
-	if (ep->sync_source)
-		WRITE_ONCE(ep->sync_source->sync_sink, NULL);
-
-	if (!atomic_dec_return(&ep->running))
+	if (!atomic_dec_return(&ep->running)) {
+		if (ep->sync_source)
+			WRITE_ONCE(ep->sync_source->sync_sink, NULL);
 		stop_urbs(ep, false);
+	}
 }
 
 /**
-- 
2.26.2