On Sun, 30 Sep 2012, Lassi Väätämöinen wrote: > Ok, cool. I did some further googling about this OHCI issue, and I came > across one Gentoo forum thread (too bad I can't find it right now). And > they were discussing the same issue: apparently (at least) with the > 2.6-series kernels the Geforce 8200 OHCI controller, which is what I > have, did not have these issues. (Due to driver workarounds?) Really? That's surprising. For that matter, you said in the original bug report that it worked with Ubuntu 11.04. Is that still true? If it is, I'd sure like to know what change was responsible for the current failures. > Anyways, I tried plugging the MobilePre through a cheap-o Belkin USB 2.0 > hub to my PC. And since that I have been running the Ardour playback > more than 15mins! > > So apparently the USB 2.0 hub has a "transaction translation" going on, > when connecting a USB 1.1 device to it. And due to the translation, the > 1.1 device shows up as USB 2.0 (EHCI) device to the OS/driver. Did I > get this correctly? Like Peter said, the OS is still aware of the device's actual speed. The important aspect is that the computer communicates with the sound card through the hub, and the hub runs at high speed. Therefore the communication goes through the EHCI controller instead of the OHCI controller, which handles only full speed and low speed. > Anyways: thanks a bunch! Now I can finally start to debug the Jack > issues with the latencies and stuff - and hopefully eventually I get > some tracks laid down... :) Great! You're welcome. If there is a software workaround for this OHCI problem, I'd like to know about it. At the moment I can't think of any good approach. > P.S. Oh, and I will be looking into revising that usbmon.txt at some point.. By all means. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
