[PATCH] ALSA: usb-audio: Fix regression on Sony WALKMAN NW-A45 DAC

[Takashi Iwai]

We've got a regression report for USB-audio with Sony WALKMAN NW-A45
DAC device where no sound is audible on recent kernel.  The bisection
resulted in the code change wrt endpoint management, and the further
debug session revealed that it was caused by the order of the USB
audio interface.  In the earlier code, we always set up the USB
interface at first before other setups, but it was changed to be done
at the last for UAC2/3, which is more standard way, while keeping the
old way for UAC1.  OTOH, this device seems requiring the setup of the
interface at first just like UAC1.

This patch works around the regression by applying the interface setup
specifically for the WALKMAN at the beginning of the endpoint setup
procedure.  This change is written straightforwardly to be easily
backported in old kernels.  A further cleanup to move the workaround
into a generic quirk section will follow in a later patch.

Fixes: bf6313a0ff76 ("ALSA: usb-audio: Refactor endpoint management")
Cc: <stable at vger.kernel.org>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=214105
Signed-off-by: Takashi Iwai <tiwai at 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 d33685874a6b..e6d58d7674a0 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -1293,6 +1293,11 @@ int snd_usb_endpoint_configure(struct snd_usb_audio *chip,
 	 * to be set up before parameter setups
 	 */
 	iface_first = ep->cur_audiofmt->protocol == UAC_VERSION_1;
+	/* Workaround for Sony WALKMAN NW-A45 DAC;
+	 * it requires the interface setup at first like UAC1
+	 */
+	if (chip->usb_id == USB_ID(0x054c, 0x0b8c))
+		iface_first = true;
 	if (iface_first) {
 		err = endpoint_set_interface(chip, ep, true);
 		if (err < 0)
-- 
2.31.1