5.4-stable review patch. If anyone has any objections, please let me know.
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From: "Geoffrey D. Bennett" g@b4.vu
[ Upstream commit 8a15ca0ca51399b652b1bbb23b590b220cf03d62 ]
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 [ Applied retry logic around snd_usb_ctl_msg() instead of scarlett2_usb_tx() ] Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/usb/mixer_scarlett_gen2.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/sound/usb/mixer_scarlett_gen2.c +++ b/sound/usb/mixer_scarlett_gen2.c @@ -118,6 +118,8 @@ #define SCARLETT2_MIXER_MAX_VALUE \ ((SCARLETT2_MIXER_MAX_DB - SCARLETT2_MIXER_MIN_DB) * 2)
+#include <linux/delay.h> + /* map from (dB + 80) * 2 to mixer value * for dB in 0 .. 172: int(8192 * pow(10, ((dB - 160) / 2 / 20))) */ @@ -591,6 +593,8 @@ static int scarlett2_usb( u16 req_buf_size = sizeof(struct scarlett2_usb_packet) + req_size; u16 resp_buf_size = sizeof(struct scarlett2_usb_packet) + resp_size; struct scarlett2_usb_packet *req = NULL, *resp = NULL; + int retries = 0; + const int max_retries = 5; int err = 0;
req = kmalloc(req_buf_size, GFP_KERNEL); @@ -614,6 +618,7 @@ static int scarlett2_usb( if (req_size) memcpy(req->data, req_data, req_size);
+retry: err = snd_usb_ctl_msg(mixer->chip->dev, usb_sndctrlpipe(mixer->chip->dev, 0), SCARLETT2_USB_VENDOR_SPECIFIC_CMD_REQ, @@ -624,6 +629,10 @@ static int scarlett2_usb( 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, "Scarlett Gen 2 USB request result cmd %x was %d\n",