1 files changed, 57 insertions, 53 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index dd37350170bb..3381319a2b3f 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1413,13 +1413,6 @@ iso_stream_schedule (
                 goto fail;
         }
 
-        if (stream->depth + span > mod) {
-                ehci_dbg (ehci, "request %p would overflow (%d+%d>%d)\n",
-                        urb, stream->depth, span, mod);
-                status = -EFBIG;
-                goto fail;
-        }
-
         now = ehci_readl(ehci, &ehci->regs->frame_index) & (mod - 1);
 
         /* Typical case: reuse current schedule, stream is still active.
@@ -1428,7 +1421,7 @@ iso_stream_schedule (
          * slot in the schedule, implicitly assuming URB_ISO_ASAP.
          */
         if (likely (!list_empty (&stream->td_list))) {
-                start = stream->next_uframe;
+                u32     excess;
 
                 /* For high speed devices, allow scheduling within the
                  * isochronous scheduling threshold.  For full speed devices
@@ -1440,21 +1433,23 @@ iso_stream_schedule (
                 else
                         next = now;
 
-                /* Fell behind (by up to twice the slop amount)? */
-                if (((start - next) & (mod - 1)) >=
-                                mod - 2 * SCHEDULE_SLOP)
-                        start += period * DIV_ROUND_UP(
-                                        (next - start) & (mod - 1),
-                                        period);
-
-                /* Tried to schedule too far into the future? */
-                if (unlikely(((start - now) & (mod - 1)) + span
-                                        >= mod - 2 * SCHEDULE_SLOP)) {
+                /* Fell behind (by up to twice the slop amount)?
+                 * We decide based on the time of the last currently-scheduled
+                 * slot, not the time of the next available slot.
+                 */
+                excess = (stream->next_uframe - period - next) & (mod - 1);
+                if (excess >= mod - 2 * SCHEDULE_SLOP)
+                        start = next + excess - mod + period *
+                                        DIV_ROUND_UP(mod - excess, period);
+                else
+                        start = next + excess + period;
+                if (start - now >= mod) {
+                        ehci_dbg(ehci, "request %p would overflow (%d+%d >= %d)\n",
+                                        urb, start - now - period, period,
+                                        mod);
                         status = -EFBIG;
                         goto fail;
                 }
-                stream->next_uframe = start;
-                goto ready;
         }
 
         /* need to schedule; when's the next (u)frame we could start?
@@ -1463,51 +1458,60 @@ iso_stream_schedule (
          * can also help high bandwidth if the dma and irq loads don't
          * jump until after the queue is primed.
          */
-        start = SCHEDULE_SLOP + (now & ~0x07);
-        start &= mod - 1;
-        stream->next_uframe = start;
-
-        /* NOTE:  assumes URB_ISO_ASAP, to limit complexity/bugs */
-
-        /* find a uframe slot with enough bandwidth */
-        for (; start < (stream->next_uframe + period); start++) {
-                int             enough_space;
-
-                /* check schedule: enough space? */
-                if (stream->highspeed)
-                        enough_space = itd_slot_ok (ehci, mod, start,
-                                        stream->usecs, period);
-                else {
-                        if ((start % 8) >= 6)
-                                continue;
-                        enough_space = sitd_slot_ok (ehci, mod, stream,
-                                        start, sched, period);
+        else {
+                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++) {
+
+                        /* check schedule: enough space? */
+                        if (stream->highspeed) {
+                                if (itd_slot_ok(ehci, mod, start,
+                                                stream->usecs, period))
+                                        break;
+                        } else {
+                                if ((start % 8) >= 6)
+                                        continue;
+                                if (sitd_slot_ok(ehci, mod, stream,
+                                                start, sched, period))
+                                        break;
+                        }
                 }
 
-                /* schedule it here if there's enough bandwidth */
-                if (enough_space) {
-                        stream->next_uframe = start & (mod - 1);
-                        goto ready;
+                /* no room in the schedule */
+                if (start == next) {
+                        ehci_dbg(ehci, "iso resched full %p (now %d max %d)\n",
+                                urb, now, now + mod);
+                        status = -ENOSPC;
+                        goto fail;
                 }
         }
 
-        /* no room in the schedule */
-        ehci_dbg (ehci, "iso %ssched full %p (now %d max %d)\n",
-                list_empty (&stream->td_list) ? "" : "re",
-                urb, now, now + mod);
-        status = -ENOSPC;
+        /* Tried to schedule too far into the future? */
+        if (unlikely(start - now + span - period
+                                >= mod - 2 * SCHEDULE_SLOP)) {
+                ehci_dbg(ehci, "request %p would overflow (%d+%d >= %d)\n",
+                                urb, start - now, span - period,
+                                mod - 2 * SCHEDULE_SLOP);
+                status = -EFBIG;
+                goto fail;
+        }
 
-fail:
-        iso_sched_free (stream, sched);
-        urb->hcpriv = NULL;
-        return status;
+        stream->next_uframe = start & (mod - 1);
 
-ready:
         /* report high speed start in uframes; full speed, in frames */
         urb->start_frame = stream->next_uframe;
         if (!stream->highspeed)
                 urb->start_frame >>= 3;
         return 0;
+
+ fail:
+        iso_sched_free(stream, sched);
+        urb->hcpriv = NULL;
+        return status;
 }
 
 /*-------------------------------------------------------------------------*/