The current TT scheduling doesn't allow to play and then record on a
full-speed
device connected to a high speed hub.
The IN iso stream can only start on the first uframe (0-2 for a 165 us)
because
of CSPLIT transactions.
For the OUT iso stream there no such restriction. uframe 0-5 are possible.
The idea of this patch is that the first uframe are precious (for IN TT iso
stream) and we should allocate the last uframes first if possible.
For that we reverse the order of uframe allocation (last uframe first).
Here an example :
hid interrupt stream
----------------------------------------------------------------------
uframe | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
----------------------------------------------------------------------
max_tt_usecs | 125 | 125 | 125 | 125 | 125 | 125 | 30 | 0 |
----------------------------------------------------------------------
used usecs on a frame | 13 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
----------------------------------------------------------------------
iso OUT stream
----------------------------------------------------------------------
uframe | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
----------------------------------------------------------------------
max_tt_usecs | 125 | 125 | 125 | 125 | 125 | 125 | 30 | 0 |
----------------------------------------------------------------------
used usecs on a frame | 13 | 125 | 39 | 0 | 0 | 0 | 0 | 0 |
----------------------------------------------------------------------
There no place for iso IN stream (uframe 0-2 are used) and we got "cannot
submit datapipe for urb 0, error -28: not enough bandwidth" error.
With the patch this become.
iso OUT stream
----------------------------------------------------------------------
uframe | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
----------------------------------------------------------------------
max_tt_usecs | 125 | 125 | 125 | 125 | 125 | 125 | 30 | 0 |
----------------------------------------------------------------------
used usecs on a frame | 13 | 0 | 0 | 0 | 125 | 39 | 0 | 0 |
----------------------------------------------------------------------
iso IN stream
----------------------------------------------------------------------
uframe | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
----------------------------------------------------------------------
max_tt_usecs | 125 | 125 | 125 | 125 | 125 | 125 | 30 | 0 |
----------------------------------------------------------------------
used usecs on a frame | 13 | 0 | 125 | 40 | 125 | 39 | 0 | 0 |
----------------------------------------------------------------------
Signed-off-by: Matthieu Castet <matthieu.castet@xxxxxxxxxx>
Signed-off-by: Thomas Poussevin <thomas.poussevin@xxxxxxxxxx>
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 724ba71..6ca99b6 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1455,9 +1455,10 @@ iso_stream_schedule (
/* NOTE: assumes URB_ISO_ASAP, to limit complexity/bugs */
/* find a uframe slot with enough bandwidth */
- next = start + period;
- for (; start < next; start++) {
-
+ next = start;
+ start += period;
+ do {
+ start--;
/* check schedule: enough space? */
if (stream->highspeed) {
if (itd_slot_ok(ehci, mod, start,
@@ -1470,7 +1471,7 @@ iso_stream_schedule (
start, sched, period))
break;
}
- }
+ } while (start > next);
/* no room in the schedule */
if (start == next) {
