6.6-stable review patch. If anyone has any objections, please let me know.
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From: Geoffrey D. Bennett g@b4.vu
commit 8a15ca0ca51399b652b1bbb23b590b220cf03d62 upstream.
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 f406005e162b ("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: 9e4d5c1be21f ("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: Geoffrey D. Bennett g@b4.vu Link: https://patch.msgid.link/aIdDO6ld50WQwNim@m.b4.vu Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/usb/mixer_scarlett2.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/sound/usb/mixer_scarlett2.c +++ b/sound/usb/mixer_scarlett2.c @@ -1279,6 +1279,8 @@ 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); @@ -1302,10 +1304,15 @@ 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",