Hi all,
I am using the MOTU Ultralite AVB USB audio interface. With recent
firmwares MOTU uses implicit feedback. Kernel 5.8-rc6 can handle it when
I apply the attached patch with the MOTU signatures.
But both with the old and the new firmware there is an occasional modulo
8 output channel hopping. What goes out to system:playback_1 in jackd
ends on channel 1, 9 or 17 in the interface. Same for system:playback_2.
I can force a hop when changing jackd's buffer size on the fly with
jack_bufsize.
One user reports this issue with ALSA clients, too, so it's probably no
jackd issue.
Since I never found this issue reported from a Windows or Mac user
it may be buried deep in the ALSA kernel code.
For me it seems that flaws/timeouts in the USB communication force this
hopping in the ALSA kernel.
Any ideas how to find out where the hopping happens?
sound/usb/endpoint.c ?
sound/usb/stream.c?
Regards
Holger
--- sound/usb/clock.c.orig 2020-07-25 23:39:23.686915955 +0200
+++ sound/usb/clock.c 2020-07-26 00:03:20.077034626 +0200
@@ -186,7 +186,8 @@
* Sample rate changes takes more than 2 seconds for this device. Clock
* validity request returns false during that period.
*/
- if (chip->usb_id == USB_ID(0x07fd, 0x0004)) {
+ if (chip->usb_id == USB_ID(0x07fd, 0x0004) ||
+ chip->usb_id == USB_ID(0x07fd, 0x0005)) {
count = 0;
while ((!ret) && (count < 50)) {
--- sound/usb/pcm.c.orig 2020-07-25 23:42:57.267196819 +0200
+++ sound/usb/pcm.c 2020-07-25 23:42:28.958577798 +0200
@@ -366,6 +366,10 @@
ep = 0x84;
ifnum = 0;
goto add_sync_ep_from_ifnum;
+ case USB_ID(0x07fd, 0x0005): /* MOTU AVB Series */
+ ep = 0x87;
+ ifnum = 2;
+ goto add_sync_ep_from_ifnum;
case USB_ID(0x07fd, 0x0008): /* MOTU M Series */
case USB_ID(0x31e9, 0x0002): /* Solid State Logic SSL2+ */
case USB_ID(0x0d9a, 0x00df): /* RTX6001 */
