From 3753fcc22974affa26160ce1c46a6ebaaaa86758 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 31 May 2022 15:07:49 +0200
Subject: [PATCH] ALSA: usb-audio: Optimize TEAC clock quirk
Git-commit: 3753fcc22974affa26160ce1c46a6ebaaaa86758
Patch-mainline: v5.19-rc1
References: git-fixes

Maris found out that the quirk for TEAC devices to work around the
clock setup is needed to apply only when the base clock is changed,
e.g. from 48000-based clocks (48000, 96000, 192000, 384000) to
44100-based clocks (44100, 88200, 176400, 352800), or vice versa,
while switching to another clock with the same base clock doesn't need
the (forcible) interface setup.

This patch implements the optimization for the TEAC clock quirk to
avoid the unnecessary interface re-setup.

Fixes: 5ce0b06ae5e6 ("ALSA: usb-audio: Workaround for clock setup on TEAC devices")
Reported-by: Maris Abele <maris7abele@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220531130749.30357-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/clock.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -675,9 +675,13 @@ static int set_sample_rate_v2v3(struct s
 	}
 
 	/* FIXME - TEAC devices require the immediate interface setup */
-	if (rate != prev_rate && USB_ID_VENDOR(chip->usb_id) == 0x0644) {
-		usb_set_interface(chip->dev, fmt->iface, fmt->altsetting);
-		msleep(50);
+	if (USB_ID_VENDOR(chip->usb_id) == 0x0644) {
+		bool cur_base_48k = (rate % 48000 == 0);
+		bool prev_base_48k = (prev_rate % 48000 == 0);
+		if (cur_base_48k != prev_base_48k) {
+			usb_set_interface(chip->dev, fmt->iface, fmt->altsetting);
+			msleep(50);
+		}
 	}
 
 validation: