Dear Alan, Below is my comments. 2011/6/1 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > On Wed, 1 Jun 2011, Soho Soho123 wrote: > >> Dear Alan, >> >> >> We have questions: >> We still do not get unstanding about :why we get -FEBIG error when uvc >> driver re-submit urb yet. >> Because we try to use another platform that CPU is faster. The error >> is still occur. >> And,the amount of URB is 5 totally. >> the another platform : CPU 620MHz, RAM 64MB > > Do you still see "now" > stream->next_uframe + 160? Soho: Yes, you could check the picture that I attached in last e-mail. > >> if each urb must use 5 iTDs, then totally 25 iTDs will be occupied in >> schedule list. The max schedule list is also large enough for that. >> And the new urb will be submit when the previous urb had complete. >> it is strange why urb submit is too late: in iso_stream_schedule() >> start - now is negative >> Do you have idea? > > Look at an example you posted earlier: > > [1943592448] iso_stream_schedule:line=1514, request 81631800 would overflow (3908+31 >= 3936) > [1943592448] iso_stream_schedule > [1943592448] mod=4096, span=32 > [1943592448] now=1195 > [1943592448] start=5103 > [1943592448] next=1195 > [1943592448] period=1 > [1943592448] excess=3907 > [1943592448] stream->next_uframe=1007 > [1943592448] uvcvideo: Failed to resubmit video URB (-27). > > This means that the last URB ended in microframe 1006. The URB > being submitted should start in microframe 1007. But "now" indicates > that the current microframe is 1195, so the URB was submitted 188 > microframes late! That's more than 23 ms after the previous URB > completed, so you have an interrupt latency of 23 ms or more. > >> About the precision of timestamp that I post from usbmon. >> the precision is in microsecond, do you mean nano is needed, right? > > No. Look at the timestamps; you'll see that even though the times > printed are in microseconds, the last four digits are always 2448. > (That's also true in the log messages above.) This means the actual > precision is only 10 ms. > Soho: in our platform the time precision is 10ms per tick . > 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
