On Friday 07 January 2005 4:23 am, Torsten Landschoff wrote: > Hi Oliver, > > On Fri, Jan 07, 2005 at 12:37:26PM +0100, Oliver Brandt wrote: > > [USB Audio problems over USB 2.0 hub] > > > I've read that iso transfer and transaction translation have something > > to do with it and that transaction translation is not fully implemented > > yet (I'm using kernel 2.6.10). Are there any patches available I should > > use? > > Actually the problem AFAIU is that the audio device is managed by a > transaction translator in the hub. Therefore isochronous data transfer > at full speed gets more complicated.
That bug's been there for a while, but not many folk have reported it. However, a couple weeks back Craig Nadler <[EMAIL PROTECTED]> turned up what could be the root cause: >>> the scanning loop for the periodic list >>> misses completed SITDs due to a race condition. The missed SITDs have not >>> been marked as completed at the time they were scanned then the frame >>> counter advanced before the scanning loop was finished. In this case the >>> scanning loop will not rescan TDs in that frame and the EHCI driver will >>> hang waiting for the TD to be removed by the scanning loop. There are two >>> fixes that I've looked at. The first one stops the next_frame field in the >>> ehci structure from being incremented passed a frame with an uncompleted TD. >>> The second fix would stop the next_frame field from being incremented passed >>> the frame that's current at the beginning of the scanning loop. Which could be what's causing this; when I saw similar problems they were (a) intermittent == race-like, (b) never on the very regular stress loads I used to test that those split ISO transfers, and (c) only on ISO transfers which were split up over several microframes. (When going through a transaction translator, an ISO-OUT transfer gets split up into 188 byte fragments, one per microframe. So transfers of 189 bytes or more would be affected.) That second approach to a fix sounds straightforward. Anyone feel like trying to provide a patch? - Dave ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
