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authorThomas Poussevin <thomas.poussevin@parrot.com>2011-10-27 18:46:48 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-26 09:08:38 -0800
commitf0cc710a6dec5b808a6f13f1f8853c094fce5f12 (patch)
treee804b565016a5e398ef0acac109ebe6d001a6a72
parentce0e4cbdc4e962aefc25bde683c415e25ed45ee6 (diff)
USB: EHCI: fix HUB TT scheduling issue with iso transfer
commit 811c926c538f7e8d3c08b630dd5844efd7e000f6 upstream. 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@parrot.com> Signed-off-by: Thomas Poussevin <thomas.poussevin@parrot.com> Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/host/ehci-sched.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 29bec34973b9..afef3df9757d 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1480,10 +1480,15 @@ 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++) {
-
+ /* find a uframe slot with enough bandwidth.
+ * Early uframes are more precious because full-speed
+ * iso IN transfers can't use late uframes,
+ * and therefore they should be allocated last.
+ */
+ next = start;
+ start += period;
+ do {
+ start--;
/* check schedule: enough space? */
if (stream->highspeed) {
if (itd_slot_ok(ehci, mod, start,
@@ -1496,7 +1501,7 @@ iso_stream_schedule (
start, sched, period))
break;
}
- }
+ } while (start > next);
/* no room in the schedule */
if (start == next) {