On Thu, 27 Aug 2009, Julie Zhu wrote:
> > What do you mean by "constantly"? scan_periodic should be called only
> > when an interrupt occurs, which should be only when one of those 2
> URBs
> > completes. Therefore scan_periodic should be called only twice.
> >
>
> Because the HS hub (FS hub also, although tests pass through FS hubs) is
> connected to the host controller, therefore, periodic schedule is
> enabled all the time. That is why scan_periodic is called constantly. I
> think it comes from ehci_work().
You can prevent this from happening so often by commenting out the line
in ehci_watchdog() where it calls ehci_work().
> I do see that scan_periodic() updates now_uframe, and my prints (which
> messed up all the timing therefore not much use) show that with HS hub,
> often now_uframe is incremented over clock, at the end of the procedure,
> inside else:
You left out some important code:
if (now_uframe == clock) {
...
> } else {
> now_uframe++; /* this one sometimes pass over
> clock without round up happening*/
> now_uframe %= mod;
> }
> } /* end of for(;;) */
> } /* end of scan_periodic() */
So I don't see how this can cause now_uframe to pass over clock.
> If that is true (which I will verify), then scan_periodic could scan
> ahead of frame index. The potential reason for this to happen could be
> the interrupt from HS hub transfers, which hardware trace showed that
> the submitted sitd's are interrupted by HS hub interrupt, and missing
I don't understand. Are you talking about the URB for the hub's
interrupt-IN endpoint? Do you mean that completion of this URB is
somehow interfering with scan_periodic()?
> sitd's happened afterwards. Although, at this point, we are not sure why
> it is so.
>
> > > I wonder whether the test setting is correct?
> >
> > What test setting?
> >
> The test setting of submitting 50 packets a time. I do not see anything
> is incorrect.
Since it works with a regular EHCI controller, it probably is correct.
Alan Stern
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