On Thu, 2 Jun 2011, Soho Soho123 wrote: > Dear Alan, > > in this e-mail that you mentioned below: > > linux 2.6.30 has bug, it can not check wrong schedule index for re-submit urb. > But today we do the verification: > We measure CPU cycles for : > 1. decode function in UVC complete call back function > 2. big for loop in scan_periodic > We compare the result between 2.6.30 and update code we used. > UVC driver is the same, the big difference is > A: 2.6.30: NO any update for USB subsystem and usb host driver > B: update code we used : included ehci schedule patch up to 2.6.39 > and we disable "printk" when submit urb error in iso_stream_schedule() > and complete call back function, since that will cause cpu cycle > inaccuracy. Okay, that sounds like a good idea. > ================================================= > Result: > in CPU cycle: > we do not find any strange. becasue we save some data to array, then > dump data by command. and both code does not trigger the threshold > that we set to treat error case. > it means : decode function in UVC driver and scan_periodic do not > cause long irq latency, when we use Code B for testing, IP cam is > dissconnect but the error case do not triggered. I don't understand. If the camera is disconnected from the USB bus, there's nothing to test! > ========================================================== > > it seems the irq latency is not cause. The cause mybe the check rule > for schedule index. > it seems something wrong about maintenance of iso schedule index in > new ehci code. > Do you have any idea? No, I don't know of anything wrong in the iso scheduling code. Maybe you can run a test where you print out the CPU cycle counter: Just before the start of the big "for" loop in scan_periodic() (also print out the values of now_uframe and clock); Just after the "restart:" statement label (also print out the value of now_uframe); And just after the call to itd_complete(). Try this for the 2.6.30 kernel and also with the updated ehci-hcd driver. Seeing the numbers might help me to figure out the problem. 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
