From 1803503fe963afe850b26769f5447f871b1c6f83 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 23 Nov 2020 09:53:12 +0100
Subject: [PATCH 06/41] ALSA: usb-audio: Set and clear sync EP link properly
References: bsc#1178203
Patch-mainline: v5.11-rc1
Git-commit: 1803503fe963afe850b26769f5447f871b1c6f83

The sync EP setup isn't cleared at stopping the stream but expected to
be cleared at the next stream start.  This may leave the sync link
setup stale and can spoof wrongly when full duplex streams were
running in the implicit fb sync.  Let's initialize them properly at
start and end of the stream.

Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Link: https://lore.kernel.org/r/20201123085347.19667-7-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/pcm.c | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 2b11c2c837bf..8800ec627a73 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -238,6 +238,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
 		err = snd_usb_endpoint_start(ep);
 		if (err < 0) {
 			clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
+			ep->sync_slave = NULL;
 			return err;
 		}
 	}
@@ -253,8 +254,10 @@ static void sync_pending_stops(struct snd_usb_substream *subs)
 
 static void stop_endpoints(struct snd_usb_substream *subs)
 {
-	if (test_and_clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags))
+	if (test_and_clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
 		snd_usb_endpoint_stop(subs->sync_endpoint);
+		subs->sync_endpoint->sync_slave = NULL;
+	}
 
 	if (test_and_clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags))
 		snd_usb_endpoint_stop(subs->data_endpoint);
@@ -471,26 +474,10 @@ static int set_sync_endpoint(struct snd_usb_substream *subs,
 	bool implicit_fb;
 	int err;
 
-	/* we need a sync pipe in async OUT or adaptive IN mode */
-	/* check the number of EP, since some devices have broken
-	 * descriptors which fool us.  if it has only one EP,
-	 * assume it as adaptive-out or sync-in.
-	 */
 	attr = fmt->ep_attr & USB_ENDPOINT_SYNCTYPE;
 
-	if ((is_playback && (attr != USB_ENDPOINT_SYNC_ASYNC)) ||
-		(!is_playback && (attr != USB_ENDPOINT_SYNC_ADAPTIVE))) {
-
-		/*
-		 * In these modes the notion of sync_endpoint is irrelevant.
-		 * Reset pointers to avoid using stale data from previously
-		 * used settings, e.g. when configuration and endpoints were
-		 * changed
-		 */
-
-		subs->sync_endpoint = NULL;
-		subs->data_endpoint->sync_master = NULL;
-	}
+	subs->sync_endpoint = NULL;
+	subs->data_endpoint->sync_master = NULL;
 
 	err = set_sync_ep_implicit_fb_quirk(subs, dev, altsd, attr);
 	if (err < 0)
@@ -939,6 +926,11 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 		sync_pending_stops(subs);
 		snd_usb_endpoint_deactivate(subs->sync_endpoint);
 		snd_usb_endpoint_deactivate(subs->data_endpoint);
+		if (subs->data_endpoint) {
+			subs->data_endpoint->sync_master = NULL;
+			subs->data_endpoint = NULL;
+		}
+		subs->sync_endpoint = NULL;
 		snd_usb_unlock_shutdown(subs->stream->chip);
 	}
 
-- 
2.16.4