USB: ehci completes high speed ISO URBs sooner

This has some bugfixes for the EHCI driver's ISO transfer scanning
logic.  It was leaving ITDs and SITDs on the schedule too long, for
a few different reasons, which caused trouble.

  (a)	Look at all microframes for high speed transfers, not just
	the ones we expect to have finished.  This way transfers
	ending mid-frame will complete without needing another IRQ.
	This also minimizes bogus scheduling underruns (e.g. EL2NSYNC).

  (b)	When we encounter an ISO transfer (either speed, but this
	hits mostly at full speed) that's not yet been completed,
	immediately stop scanning; we've caught up to the hardware,
	no matter what other indications might say.

  (c)	Always clean up ITDs (for high speed transfers) when the HC
	is no longer running.

I'm not sure whether the last one has been observed before, but both
the others have been reported with "real world" audio and video code.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-sched.c

@@ -2123,17 +2123,9 @@ scan_periodic (struct ehci_hcd *ehci)
 	for (;;) {
 		union ehci_shadow	q, *q_p;
 		__hc32			type, *hw_p;
-		unsigned		uframes;
+		unsigned		incomplete = false;
 
-		/* don't scan past the live uframe */
 		frame = now_uframe >> 3;
-		if (frame == (clock >> 3))
-			uframes = now_uframe & 0x07;
-		else {
-			/* safe to scan the whole frame at once */
-			now_uframe |= 0x07;
-			uframes = 8;
-		}
 
 restart:
 		/* scan each element in frame's queue for completions */
@@ -2171,12 +2163,15 @@ restart:
 				q = q.fstn->fstn_next;
 				break;
 			case Q_TYPE_ITD:
-				/* skip itds for later in the frame */
+				/* If this ITD is still active, leave it for
+				 * later processing ... check the next entry.
+				 */
 				rmb ();
-				for (uf = live ? uframes : 8; uf < 8; uf++) {
+				for (uf = 0; uf < 8 && live; uf++) {
 					if (0 == (q.itd->hw_transaction [uf]
 							& ITD_ACTIVE(ehci)))
 						continue;
+					incomplete = true;
 					q_p = &q.itd->itd_next;
 					hw_p = &q.itd->hw_next;
 					type = Q_NEXT_TYPE(ehci,
@@ -2184,10 +2179,12 @@ restart:
 					q = *q_p;
 					break;
 				}
-				if (uf != 8)
+				if (uf < 8 && live)
 					break;
 
-				/* this one's ready ... HC won't cache the
+				/* Take finished ITDs out of the schedule
+				 * and process them:  recycle, maybe report
+				 * URB completion.  HC won't cache the
 				 * pointer for much longer, if at all.
 				 */
 				*q_p = q.itd->itd_next;
@@ -2198,8 +2195,12 @@ restart:
 				q = *q_p;
 				break;
 			case Q_TYPE_SITD:
+				/* If this SITD is still active, leave it for
+				 * later processing ... check the next entry.
+				 */
 				if ((q.sitd->hw_results & SITD_ACTIVE(ehci))
 						&& live) {
+					incomplete = true;
 					q_p = &q.sitd->sitd_next;
 					hw_p = &q.sitd->hw_next;
 					type = Q_NEXT_TYPE(ehci,
@@ -2207,6 +2208,11 @@ restart:
 					q = *q_p;
 					break;
 				}
+
+				/* Take finished SITDs out of the schedule
+				 * and process them:  recycle, maybe report
+				 * URB completion.
+				 */
 				*q_p = q.sitd->sitd_next;
 				*hw_p = q.sitd->hw_next;
 				type = Q_NEXT_TYPE(ehci, q.sitd->hw_next);
@@ -2232,7 +2238,14 @@ restart:
 			}
 		}
 
-		/* stop when we catch up to the HC */
+		/* If we can tell we caught up to the hardware, stop now.
+		 * We can't advance our scan without collecting the ISO
+		 * transfers that are still pending in this frame.
+		 */
+		if (incomplete && HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
+			ehci->next_uframe = now_uframe;
+			break;
+		}
 
 		// FIXME:  this assumes we won't get lapped when
 		// latencies climb; that should be rare, but...