EHCI : Fix a regression in the ISO scheduler

commit e3420901eba65b1c46bed86d360e3a8685d20734 upstream.

Fix a regression that was introduced by commit
811c926c538f7e8d3c08b630dd5844efd7e000f6 (USB: EHCI: fix HUB TT scheduling
issue with iso transfer).

We detect an error if next == start, but this means uframe 0 can't be allocated
anymore for iso transfer...

Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 063c630d246731383e2c097cb63f2a107f36bd76..8949b239deccac8ab31f7a0a2c1560abef8f3575 100644 (file)
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1479,30 +1479,36 @@ iso_stream_schedule (
         * jump until after the queue is primed.
         */
        else {
+               int done = 0;
                start = SCHEDULE_SLOP + (now & ~0x07);
 
                /* 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,
                                                stream->usecs, period))
-                                       break;
+                                       done = 1;
                        } else {
                                if ((start % 8) >= 6)
                                        continue;
                                if (sitd_slot_ok(ehci, mod, stream,
                                                start, sched, period))
-                                       break;
+                                       done = 1;
                        }
-               }
+               } while (start > next && !done);
 
                /* no room in the schedule */
-               if (start == next) {
+               if (!done) {
                        ehci_dbg(ehci, "iso resched full %p (now %d max %d)\n",
                                urb, now, now + mod);
                        status = -ENOSPC;