On 09/15/2010 09:59 AM, Jeremy Jongepier wrote: > 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 I've checked with lsusb. Only two buses, and even if I try the least crowded bus and use rtirq to prioritize that bus my UA-25 refuses to work in duplex mode. So it might be that I'm behind a hub after all and it's probably got nothing to do with a buggy USB chipset in my case. But I already had a suspicion that USB soundcards wouldn't work on this machine so I've equipped it with a decent FireWire PCIe card (the one on the motherboard is crap also) and a FireWire soundcard. Best, Jeremy _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
