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USB: fix latency in uhci-hcd and ohci-hcd
Commitsc44b225077
(UHCI: implement new semantics for URB_ISO_ASAP) and6a41b4d3fe
(OHCI: implement new semantics for URB_ISO_ASAP) increased the latency for isochronous URBs in uhci-hcd and ohci-hcd respectively to 2 milliseconds, in an attempt to avoid underruns. It turns out that not only was this unnecessary -- 1-ms latency works okay -- it also causes problems with certain application loads such as real-time audio. This patch changes the latency for both drivers back to 1 ms. This should be applied to -stable kernels going back to 3.8. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: Joe Rayhawk <jrayhawk@fairlystable.org> CC: Clemens Ladisch <clemens@ladisch.de> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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2 changed files with 2 additions and 2 deletions
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@ -233,7 +233,7 @@ static int ohci_urb_enqueue (
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urb->start_frame = frame;
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}
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} else if (ed->type == PIPE_ISOCHRONOUS) {
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u16 next = ohci_frame_no(ohci) + 2;
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u16 next = ohci_frame_no(ohci) + 1;
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u16 frame = ed->last_iso + ed->interval;
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/* Behind the scheduling threshold? */
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@ -1287,7 +1287,7 @@ static int uhci_submit_isochronous(struct uhci_hcd *uhci, struct urb *urb,
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return -EINVAL; /* Can't change the period */
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} else {
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next = uhci->frame_number + 2;
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next = uhci->frame_number + 1;
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/* Find the next unused frame */
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if (list_empty(&qh->queue)) {
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