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Commit 6a41b4d3 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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OHCI: implement new semantics for URB_ISO_ASAP 



This patch (as1614) updates the isochronous scheduling in ohci-hcd to
match the new semantics for URB_ISO_ASAP.  Testing revealed a hardware
bug in the way my OHCI controller handles expired isochronous TDs;
consequently the patch tries hard to avoid creating them (unlike the
ehci-hcd and uhci-hcd drivers).

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c44b2250

drivers/usb/host/ohci-hcd.c

+32 −4
Original line number Diff line number Diff line
@@ -231,13 +231,41 @@ static int ohci_urb_enqueue ( 
			frame &= ~(ed->interval - 1);

			frame |= ed->branch;

			urb->start_frame = frame;

		}

	} else if (ed->type == PIPE_ISOCHRONOUS) {

		u16	next = ohci_frame_no(ohci) + 2;

		u16	frame = ed->last_iso + ed->interval;



		/* Behind the scheduling threshold? */

		if (unlikely(tick_before(frame, next))) {



			/* USB_ISO_ASAP: Round up to the first available slot */

			if (urb->transfer_flags & URB_ISO_ASAP)

				frame += (next - frame + ed->interval - 1) &

						-ed->interval;



			/*

			 * Not ASAP: Use the next slot in the stream.  If

			 * the entire URB falls before the threshold, fail.

			 */

			else if (tick_before(frame + ed->interval *

					(urb->number_of_packets - 1), next)) {

				retval = -EXDEV;

				usb_hcd_unlink_urb_from_ep(hcd, urb);

				goto fail;

			}



			/* yes, only URB_ISO_ASAP is supported, and

			 * urb->start_frame is never used as input.

			/*

			 * Some OHCI hardware doesn't handle late TDs

			 * correctly.  After retiring them it proceeds to

			 * the next ED instead of the next TD.  Therefore

			 * we have to omit the late TDs entirely.

			 */

			urb_priv->td_cnt = DIV_ROUND_UP(next - frame,

					ed->interval);

		}

		urb->start_frame = frame;

	}

	} else if (ed->type == PIPE_ISOCHRONOUS)

		urb->start_frame = ed->last_iso + ed->interval;



	/* fill the TDs and link them to the ed; and

	 * enable that part of the schedule, if needed

drivers/usb/host/ohci-q.c

+2 −2
Original line number Diff line number Diff line
@@ -596,7 +596,6 @@ static void td_submit_urb ( 
		urb_priv->ed->hwHeadP &= ~cpu_to_hc32 (ohci, ED_C);

	}



	urb_priv->td_cnt = 0;

	list_add (&urb_priv->pending, &ohci->pending);



	if (data_len)
@@ -672,7 +671,8 @@ static void td_submit_urb ( 
	 * we could often reduce the number of TDs here.

	 */

	case PIPE_ISOCHRONOUS:

		for (cnt = 0; cnt < urb->number_of_packets; cnt++) {

		for (cnt = urb_priv->td_cnt; cnt < urb->number_of_packets;

				cnt++) {

			int	frame = urb->start_frame;



			// FIXME scheduling should handle frame counter