Commit 8a15ca0c authored by Geoffrey D. Bennett's avatar Geoffrey D. Bennett Committed by Takashi Iwai
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ALSA: scarlett2: Add retry on -EPROTO from scarlett2_usb_tx() 

During communication with Focusrite Scarlett Gen 2/3/4 USB audio
interfaces, -EPROTO is sometimes returned from scarlett2_usb_tx(),
snd_usb_ctl_msg() which can cause initialisation and control
operations to fail intermittently.

This patch adds up to 5 retries in scarlett2_usb(), with a delay
starting at 5ms and doubling each time. This follows the same approach
as the fix for usb_set_interface() in endpoint.c (commit f406005e
("ALSA: usb-audio: Add retry on -EPROTO from usb_set_interface()")),
which resolved similar -EPROTO issues during device initialisation,
and is the same approach as in fcp.c:fcp_usb().

Fixes: 9e4d5c1b ("ALSA: usb-audio: Scarlett Gen 2 mixer interface")
Closes: https://github.com/geoffreybennett/linux-fcp/issues/41


Cc: stable@vger.kernel.org
Signed-off-by: default avatarGeoffrey D. Bennett <g@b4.vu>
Link: https://patch.msgid.link/aIdDO6ld50WQwNim@m.b4.vu


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent bd7814a4

sound/usb/mixer_scarlett2.c

+7 −0
Original line number Diff line number Diff line
@@ -2351,6 +2351,8 @@ static int scarlett2_usb( 
	struct scarlett2_usb_packet *req, *resp = NULL;

	size_t req_buf_size = struct_size(req, data, req_size);

	size_t resp_buf_size = struct_size(resp, data, resp_size);

	int retries = 0;

	const int max_retries = 5;

	int err;



	req = kmalloc(req_buf_size, GFP_KERNEL);
@@ -2374,10 +2376,15 @@ static int scarlett2_usb( 
	if (req_size)

		memcpy(req->data, req_data, req_size);



retry:

	err = scarlett2_usb_tx(dev, private->bInterfaceNumber,

			       req, req_buf_size);



	if (err != req_buf_size) {

		if (err == -EPROTO && ++retries <= max_retries) {

			msleep(5 * (1 << (retries - 1)));

			goto retry;

		}

		usb_audio_err(

			mixer->chip,

			"%s USB request result cmd %x was %d\n",