On 09/14/2010 06:26 PM, Monty Montgomery wrote: > On Tue, Sep 14, 2010 at 8:29 AM, Jeremy Jongepier <jeremy@xxxxxxxxxxxxxx> wrote: >> On 09/14/2010 02:23 PM, Clemens Ladisch wrote: >>> Jeremy Jongepier wrote: >>>> cannot submit datapipe for urb 0, error -28: not enough bandwidth >>> >>> Is CONFIG_USB_EHCI_TT_NEWSCHED enabled in your kernel's configuration? >>> >>> Can you try with or without a hub? >>> >> >> I can't try with a hub, I don't have any. > > The bandwidth has been fragmented by other devices. USB-1 audio > devices require large _contiguous_ blocks of bandwidth schedule, and a > mouse or whatever that has carved its tiny little block out of the > middle of the bandwidth schedule makes all the bandwidth on either > side useless to an isochronous device. Simply unplugging it (or > whatever caused the scheduling problem) is not enough; the schedule > remains fragmented, as the linux EHCI driver does not know how to > reconsolidate fragmented bandwidth chunks. You have to rmmod EHCI or > reboot to get a fresh start. > > It's possible you're on a hub and don't know it. Most machines with > multiple USB ports are actually using a single controller and a built > in hub. Hubs make things *far* worse, as the hub is a dumb puppet > controlled entirely by the host controller, and Linux's hub scheduling > algorithm (even the 'new improved' one mentioned above) is rather > poor. I wrote a new one years ago that approached theoretical maximum > efficiency and could rebalance/reconsolidate the schedule, but I > couldn't keep up with repatching it during the complete free-for-all > that has been kernel 2.6 (I'd literally spent months of full-time work > *just* keeping up with the churn) and it was dropped from -mm. > > Monty Hello Monty, I've tried with all the ports on the machine but alas, forgot to run lsusb so I don't know how many USB buses there are available. I use a real-time kernel with rtirq though and will prioritize USB to see if that helps. Best, Jeremy _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
