On Mon, 10 Dec 2012, Piergiorgio Sartor wrote:
> > Here's an idea. This just occurred to me. Maybe when the driver is
> > waiting for the async schedule to turn off, new QH's should not be
> > added to the schedule. The driver could wait and add them after the
> > schedule was off. I didn't do it that way because it would slow things
> > down and add complexity, but maybe that's what the nVidia hardware
> > needs.
>
> How difficult is it?
> Would it be possible to have as a patch I could try?
Instead of doing this, I wrote a simpler patch that removes the limit
on the number of polls. It also writes a debugging message whenever
more than 20 ms of polling is needed, so we can see what your
controller is actually doing.
Alan Stern
Index: usb-3.7/drivers/usb/host/ehci-timer.c
===================================================================
--- usb-3.7.orig/drivers/usb/host/ehci-timer.c
+++ usb-3.7/drivers/usb/host/ehci-timer.c
@@ -113,14 +113,15 @@ static void ehci_poll_ASS(struct ehci_hc
if (want != actual) {
- /* Poll again later, but give up after about 20 ms */
- if (ehci->ASS_poll_count++ < 20) {
- ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
- return;
- }
- ehci_dbg(ehci, "Waited too long for the async schedule status
(%x/%x), giving up\n",
- want, actual);
+ /* Poll again later */
+ ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
+ ++ehci->ASS_poll_count;
+ return;
}
+
+ if (ehci->ASS_poll_count > 20)
+ ehci_dbg(ehci, "ASS poll count reached %d\n",
+ ehci->ASS_poll_count);
ehci->ASS_poll_count = 0;
/* The status is up-to-date; restart or stop the schedule as needed */
@@ -159,14 +160,14 @@ static void ehci_poll_PSS(struct ehci_hc
if (want != actual) {
- /* Poll again later, but give up after about 20 ms */
- if (ehci->PSS_poll_count++ < 20) {
- ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
- return;
- }
- ehci_dbg(ehci, "Waited too long for the periodic schedule
status (%x/%x), giving up\n",
- want, actual);
+ /* Poll again later */
+ ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
+ return;
}
+
+ if (ehci->PSS_poll_count > 20)
+ ehci_dbg(ehci, "PSS poll count reached %d\n",
+ ehci->PSS_poll_count);
ehci->PSS_poll_count = 0;
/* The status is up-to-date; restart or stop the schedule as needed */
--
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