USB: OHCI: accept very late isochronous URBs

Commit 24f531371de1 (USB: EHCI: accept very late isochronous URBs)
changed the isochronous API provided by ehci-hcd.  URBs submitted too
late, so that the time slots for all their packets have already
expired, are no longer rejected outright.  Instead the submission is
accepted, and the URB completes normally with a -EXDEV error for each
packet.  This is what client drivers expect.

This patch implements the same policy in ohci-hcd.  The change is more
complicated than it was in ehci-hcd, because ohci-hcd doesn't scan for
isochronous completions in the same way as ehci-hcd does.  Rather, it
depends on the hardware adding completed TDs to a "done queue".  Some
OHCI controller don't handle this properly when a TD's time slot has
already expired, so we have to avoid adding such TDs to the schedule
in the first place.  As a result, if the URB was submitted too late
then none of its TDs will get put on the schedule, so none of them
will end up on the done queue, so the driver will never realize that
the URB should be completed.

To solve this problem, the patch adds one to urb_priv->td_cnt for such
URBs, making it larger than urb_priv->length (td_cnt already gets set
to the number of TD's that had to be skipped because their slots have
expired).  Each time an URB is given back, the finish_urb() routine
looks to see if urb_priv->td_cnt for the next URB on the same endpoint
is marked in this way.  If so, it gives back the next URB right away.

This should be applied to all kernels containing commit 815fa7b91761
(USB: OHCI: fix logic for scheduling isochronous URBs).

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 10 deletions

diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 8f6b695af6a4..604cad1bcf9c 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/drivers/usb/host/ohci-hcd.c
@@ -216,31 +216,26 @@ static int ohci_urb_enqueue (
 			frame &= ~(ed->interval - 1);
 			frame |= ed->branch;
 			urb->start_frame = frame;
+			ed->last_iso = frame + ed->interval * (size - 1);
 		}
 	} else if (ed->type == PIPE_ISOCHRONOUS) {
 		u16	next = ohci_frame_no(ohci) + 1;
 		u16	frame = ed->last_iso + ed->interval;
+		u16	length = ed->interval * (size - 1);
 
 		/* Behind the scheduling threshold? */
 		if (unlikely(tick_before(frame, next))) {
 
-			/* USB_ISO_ASAP: Round up to the first available slot */
+			/* URB_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.
+			 * Not ASAP: Use the next slot in the stream,
+			 * no matter what.
 			 */
 			} 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;
-				}
-
 				/*
 				 * Some OHCI hardware doesn't handle late TDs
 				 * correctly.  After retiring them it proceeds
@@ -251,9 +246,16 @@ static int ohci_urb_enqueue (
 				urb_priv->td_cnt = DIV_ROUND_UP(
 						(u16) (next - frame),
 						ed->interval);
+				if (urb_priv->td_cnt >= urb_priv->length) {
+					++urb_priv->td_cnt;	/* Mark it */
+					ohci_dbg(ohci, "iso underrun %p (%u+%u < %u)\n",
+							urb, frame, length,
+							next);
+				}
 			}
 		}
 		urb->start_frame = frame;
+		ed->last_iso = frame + length;
 	}
 
 	/* fill the TDs and link them to the ed; and