Alan Stern wrote: > On Fri, 6 Jul 2007, Mike Nuss wrote: > >>> Here's what I meant. Normally SOF interrupts are disabled, but when >>> the driver gets a completion interrupt for an URB it could turn on the >>> SOF interrupt for the next frame only. Then when the next interrupt >>> occurs the driver could compare the ED states with the donelist, >>> checking for inconsistencies. >> What do you mean by 'completion interrupt for an URB?' > > For the last TD in an URB, ohci-hcd generally sets DI (DelayInterrupt) > in the first dword to a value < 7 so the HC will generate an IRQ when > the TD completes or shortly thereafter. That's the completion > interrupt. > > Alan Stern > > On the hardware side though, DI relates to how many frames the HC will wait until HccaDoneHead will be updated, and the WDH IRQ isn't sent until that happens. But since the TD never gets properly retired by the HC when this bug occurs, we never get that interrupt. The last time the interrupt would have been sent would have been after the last successful completion, would could have been several frames beforehand. So if there's only one read endpoint, I don't think this would work, unless I'm still missing something.
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