On Mon, Oct 28, 2002, anton wilson <[EMAIL PROTECTED]> wrote: > On Monday 28 October 2002 04:01 pm, Johannes Erdfelt wrote: > > On Mon, Oct 28, 2002, anton wilson <[EMAIL PROTECTED]> wrote: > > > On Friday 25 October 2002 06:36 pm, Johannes Erdfelt wrote: > > > > On Fri, Oct 25, 2002, anton wilson <[EMAIL PROTECTED]> wrote: > > > > > In a USB driver, I'm chaining ISO urbs by resubmitting the URBS in > > > > > the completion handler. I also time the calls to the urb completion > > > > > handlers using do_gettimeofday(). Most of the time, the time between > > > > > interrupts is at most 1.01 ms, but occasionally there may be a 2 ms > > > > > time inbetween interrupts. By occasional I mean 1 or 2 times every 10 > > > > > seconds. Is this normal behaviour? And what kinds of things could > > > > > cause an additional 1 ms delay between calls to the completion > > > > > handler? > > > > > > > > What HC are you using? What kernel? > > > > > > linux 2.4.18 with 0(1) - preemptive and low-latency - > > > UHCI > > > > How many Isochronous buffers are you scheduling at one time? > > > > Which UHCI driver? > > the usb-uhci module v1.275 ... > I'd say 4 per device. 2 read and 2 write > I'm not quite sure if enqueuing all 4 at once is necessary to achieve sends > and recieves every ms. That's how the driver was before it was handed to > me... The urbs are re-submitted in the completion handler. > 3 devices are being used right now.
That's probably not enough. There is no guarantee that the callback will happen quickly enough that you can reschedule it for frame afterwards. You may want to try using multiple buffers (and thusly multiple frames) per URB, or use some more URB's. JE ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
