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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 4a1d64d..cfc1da3 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/drivers/usb/host/ohci-hcd.c
@@ -231,13 +231,41 @@
frame &= ~(ed->interval - 1);
frame |= ed->branch;
urb->start_frame = frame;
-
- /* yes, only URB_ISO_ASAP is supported, and
- * urb->start_frame is never used as input.
- */
}
- } else if (ed->type == PIPE_ISOCHRONOUS)
- urb->start_frame = ed->last_iso + ed->interval;
+ } 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;
+ }
+
+ /*
+ * 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;
+ }
/* fill the TDs and link them to the ed; and
* enable that part of the schedule, if needed