Re: [Qemu-devel] [PATCH 13/31] usb-ehci: drop EXECUTING checks.

[Gerd Hoffmann]

  Hi,

> > > -#if EHCI_DEBUG == 0
> > > -    if (qemu_get_clock_ns(vm_clock) / 1000>= ehci->frame_end_usec) {
> > > -        if (async) {
> > > -            DPRINTF("FETCHENTRY: FRAME timer elapsed, exit state machine\n");
> > > -            goto out;
> > > -        } else {
> > > -            DPRINTF("FETCHENTRY: WARNING "
> > > -                    "- frame timer elapsed during periodic\n");
> > > -        }
> > > -    }
> > > -#endif
>
> This check was added to per Section 4 of the EHCI spec -- the HC should
> not start transactions that will not be completed before the end of the
> micro-frame. If you remove this what causes the EHCI model to take a
> breather?

Look at patch #8.  That brings a number of state machine changes.  One 
of them is that the async schedule stops as soon as it notices it walks 
in circles (i.e. sees a QH the second time).

> > > -    case EST_FETCHENTRY:
> > > -        /* fall through */
> >
> > Why drop this case too? As I recall that is needed for proper execution.

The async schedule doesn't pause in fetchentry state any more (also done 
by patch #8).

cheers,
  Gerd