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@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ohci-hcd.c | 36 ++++++++++++++++++++++++++++++++----
drivers/usb/host/ohci-q.c | 4 ++--
2 files changed, 34 insertions(+), 6 deletions(-)
Index: usb-3.6/drivers/usb/host/ohci-hcd.c
===================================================================
--- usb-3.6.orig/drivers/usb/host/ohci-hcd.c
+++ usb-3.6/drivers/usb/host/ohci-hcd.c
@@ -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);
}
- } else if (ed->type == PIPE_ISOCHRONOUS)
- urb->start_frame = ed->last_iso + ed->interval;
+ urb->start_frame = frame;
+ }
/* fill the TDs and link them to the ed; and
* enable that part of the schedule, if needed
Index: usb-3.6/drivers/usb/host/ohci-q.c
===================================================================
--- usb-3.6.orig/drivers/usb/host/ohci-q.c
+++ usb-3.6/drivers/usb/host/ohci-q.c
@@ -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
--
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