On Tue, 2 Jul 2013, Ming Lei wrote:
> ehci-hcd currently unlinks an interrupt QH when it becomes empty, that
> is, after its last URB completes. This works well because in almost
> all cases, the completion handler for an interrupt URB resubmits the
> URB; therefore the QH doesn't become empty and doesn't get unlinked.
>
> When we start using tasklets for URB completion, this scheme won't work
> as well. The resubmission won't occur until the tasklet runs, which
> will be some time after the completion is queued with the tasklet.
> During that delay, the QH will be empty and so will be unlinked
> unnecessarily.
>
> To prevent this problem, this patch adds a 5-ms time delay before empty
> interrupt QHs are unlinked. Most often, during that time the interrupt
> URB will be resubmitted and thus we can avoid unlinking the QH.
One little thing...
> @@ -98,7 +99,6 @@ static void ehci_enable_event(struct ehci_hcd *ehci,
> unsigned event,
> }
> }
>
> -
> /* Poll the STS_ASS status bit; see when it agrees with CMD_ASE */
> static void ehci_poll_ASS(struct ehci_hcd *ehci)
> {
This blank line should remain intact. Apart from that, the patch is
okay.
Alan Stern
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