Dear Alan, my comments below. Thanks a lot! 2011/6/2 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > On Wed, 1 Jun 2011, Soho Soho123 wrote: > >> 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. > > This means there is still too much interrupt latency. You should try > to find out how much time is spent whenever itd_complete() calls > ehci_urb_done(). Most of that time will be in the uvcvideo driver. > soho: sure, we will try to find out the location where spent more time. >> >> 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 . > > In a PC, the time precision is between 1 and 10 ms per tick. But PCs > also have high-precision timers available; apparently your platform > does not. Without high-precision timestamps, there's no way to tell > what's causing your latencies to be so large. soho:???? > Have you tried running this test on a regular PC instead of your > embedded platform? Does that work okay? > Soho: we do not test in x86 PCs. if PCs can work, but our platform can not work. It still to be fixed > One other thing you can try: Increase UVC_MAX_PACKETS to 100. soho: we will try it later. Could you explation the consideration about increase uvc max packet? > > 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
