USB: ehci: minor ISO updates, always support split ISO

Small updates to the EHCI driver's ISO support:

 - Get rid of the Kconfig option for full speed ISO.  It may
   not be perfect yet, but it hasn't appeared to be dangerous
   and pretty much every configuration wants it.

 - Instead of two places to disable an empty periodic schedule
   after an ISO transfer completes, just have one.

 - After the periodic schedule is disabled, we can short-circuit
   the schedule scan ... it can't possibly have more work to do.

Assuming a typical config with split iso enabled, the only change
in behavior should be almost unobservable:  quicker termination
of periodic scans when the schedule gets emptied.

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

drivers/usb/host/Kconfig

@@ -29,15 +29,6 @@ config USB_EHCI_HCD
 	  To compile this driver as a module, choose M here: the
 	  module will be called ehci-hcd.
 
-config USB_EHCI_SPLIT_ISO
-	bool "Full speed ISO transactions (EXPERIMENTAL)"
-	depends on USB_EHCI_HCD && EXPERIMENTAL
-	default n
-	---help---
-	  This code is new and hasn't been used with many different
-	  EHCI or USB 2.0 transaction translator implementations.
-	  It should work for ISO-OUT transfers, like audio.
-
 config USB_EHCI_ROOT_HUB_TT
 	bool "Root Hub Transaction Translators (EXPERIMENTAL)"
 	depends on USB_EHCI_HCD && EXPERIMENTAL

drivers/usb/host/ehci-sched.c

@@ -1630,16 +1630,12 @@ itd_complete (
 		BUG_ON (itd->urb == urb);
 	 */
 
-	/* give urb back to the driver ... can be out-of-order */
+	/* give urb back to the driver; completion often (re)submits */
 	dev = urb->dev;
 	ehci_urb_done(ehci, urb, 0);
 	retval = true;
 	urb = NULL;
-
-	/* defer stopping schedule; completion can submit */
 	ehci->periodic_sched--;
-	if (unlikely (!ehci->periodic_sched))
-		(void) disable_periodic (ehci);
 	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
 
 	if (unlikely (list_empty (&stream->td_list))) {
@@ -1725,8 +1721,6 @@ static int itd_submit (struct ehci_hcd *ehci, struct urb *urb,
 	return status;
 }
 
-#ifdef CONFIG_USB_EHCI_SPLIT_ISO
-
 /*-------------------------------------------------------------------------*/
 
 /*
@@ -2016,16 +2010,12 @@ sitd_complete (
 		BUG_ON (sitd->urb == urb);
 	 */
 
-	/* give urb back to the driver */
+	/* give urb back to the driver; completion often (re)submits */
 	dev = urb->dev;
 	ehci_urb_done(ehci, urb, 0);
 	retval = true;
 	urb = NULL;
-
-	/* defer stopping schedule; completion can submit */
 	ehci->periodic_sched--;
-	if (!ehci->periodic_sched)
-		(void) disable_periodic (ehci);
 	ehci_to_hcd(ehci)->self.bandwidth_isoc_reqs--;
 
 	if (list_empty (&stream->td_list)) {
@@ -2108,26 +2098,6 @@ static int sitd_submit (struct ehci_hcd *ehci, struct urb *urb,
 	return status;
 }
 
-#else
-
-static inline int
-sitd_submit (struct ehci_hcd *ehci, struct urb *urb, gfp_t mem_flags)
-{
-	ehci_dbg (ehci, "split iso support is disabled\n");
-	return -ENOSYS;
-}
-
-static inline unsigned
-sitd_complete (
-	struct ehci_hcd		*ehci,
-	struct ehci_sitd	*sitd
-) {
-	ehci_err (ehci, "sitd_complete %p?\n", sitd);
-	return 0;
-}
-
-#endif /* USB_EHCI_SPLIT_ISO */
-
 /*-------------------------------------------------------------------------*/
 
 static void
@@ -2252,8 +2222,14 @@ scan_periodic (struct ehci_hcd *ehci)
 			}
 
 			/* assume completion callbacks modify the queue */
-			if (unlikely (modified))
-				goto restart;
+			if (unlikely (modified)) {
+				if (likely(ehci->periodic_sched > 0))
+					goto restart;
+				/* maybe we can short-circuit this scan! */
+				disable_periodic(ehci);
+				now_uframe = clock;
+				break;
+			}
 		}
 
 		/* stop when we catch up to the HC */
@@ -2269,7 +2245,8 @@ scan_periodic (struct ehci_hcd *ehci)
 		if (now_uframe == clock) {
 			unsigned	now;
 
-			if (!HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
+			if (!HC_IS_RUNNING (ehci_to_hcd(ehci)->state)
+					|| ehci->periodic_sched == 0)
 				break;
 			ehci->next_uframe = now_uframe;
 			now = ehci_readl(ehci, &ehci->regs->frame_index) % mod;