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>

2 files changed, 12 insertions, 44 deletions

diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index 3a42bcd27d3..d97b16b52ef 100644
--- a/drivers/usb/host/Kconfig
+++ b/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
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 1a94e6cec41..001b2c389be 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/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 @@ done:
         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 @@ done:
         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 @@ restart:
                         }
 
                         /* 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 @@ restart:
                 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;