From cf9fb7b8737694818e783fc61e8fe220b7eaaf60 Mon Sep 17 00:00:00 2001
From: Alexander Tsoy <alexander@tsoy.me>
Date: Tue, 21 Apr 2020 22:09:08 +0300
Subject: [PATCH] ALSA: usb-audio: Apply async workaround for Scarlett 2i4 2nd gen
Git-commit: cf9fb7b8737694818e783fc61e8fe220b7eaaf60
Patch-mainline: v5.7-rc3
References: bsc#1051510

Due to rounding error driver sometimes incorrectly calculate next packet
size, which results in audible clicks on devices with synchronous playback
endpoints. For example on a high speed bus and a sample rate 44.1 kHz it
loses one sample every ~40.9 seconds. Fortunately playback interface on
Scarlett 2i4 2nd gen has a working explicit feedback endpoint, so we can
switch playback data endpoint to asynchronous mode as a workaround.

Signed-off-by: Alexander Tsoy <alexander@tsoy.me>
Link: https://lore.kernel.org/r/20200421190908.462860-1-alexander@tsoy.me
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/quirks.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 6c2dfd3bfcbf..351ba214a9d3 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -1806,6 +1806,7 @@ void snd_usb_audioformat_attributes_quirk(struct snd_usb_audio *chip,
 		 */
 		fp->attributes &= ~UAC_EP_CS_ATTR_FILL_MAX;
 		break;
+	case USB_ID(0x1235, 0x8200):  /* Focusrite Scarlett 2i4 2nd gen */
 	case USB_ID(0x1235, 0x8202):  /* Focusrite Scarlett 2i2 2nd gen */
 	case USB_ID(0x1235, 0x8205):  /* Focusrite Scarlett Solo 2nd gen */
 		/*
-- 
2.16.4