From 9902b303b5ade208b58f0dd38a09831813582211 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Sun, 9 Oct 2022 12:42:09 +0200
Subject: [PATCH] ALSA: usb-audio: Avoid unnecessary interface change at EP close
Git-commit: 9902b303b5ade208b58f0dd38a09831813582211
Patch-mainline: v6.1-rc1
References: git-fixes

We toggle USB interface at PCM prepare and reset at close.  When the
PCM isn't prepared, resetting again makes little sense.
Check the current altset and avoid unnecessary interface reset at EP
close.

Link: https://lore.kernel.org/r/20221009104212.18877-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/endpoint.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 48a3843a08f1..f21acbc9f4f4 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -32,6 +32,7 @@ struct snd_usb_iface_ref {
 	unsigned char iface;
 	bool need_setup;
 	int opened;
+	int altset;
 	struct list_head list;
 };
 
@@ -899,6 +900,9 @@ static int endpoint_set_interface(struct snd_usb_audio *chip,
 	int altset = set ? ep->altsetting : 0;
 	int err;
 
+	if (ep->iface_ref->altset == altset)
+		return 0;
+
 	usb_audio_dbg(chip, "Setting usb interface %d:%d for EP 0x%x\n",
 		      ep->iface, altset, ep->ep_num);
 	err = usb_set_interface(chip->dev, ep->iface, altset);
@@ -910,6 +914,7 @@ static int endpoint_set_interface(struct snd_usb_audio *chip,
 
 	if (chip->quirk_flags & QUIRK_FLAG_IFACE_DELAY)
 		msleep(50);
+	ep->iface_ref->altset = altset;
 	return 0;
 }
 
-- 
2.35.3