1 files changed, 34 insertions, 32 deletions

diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
index fba99b120588..c8ae199cfbb8 100644
--- a/drivers/usb/host/uhci-hcd.c
+++ b/drivers/usb/host/uhci-hcd.c
@@ -294,50 +294,50 @@ __acquires(uhci->lock)
          * and that remote wakeups should be enabled.
          */
         egsm_enable = USBCMD_EGSM;
-        uhci->RD_enable = 1;
         int_enable = USBINTR_RESUME;
         wakeup_enable = 1;
 
-        /* In auto-stop mode wakeups must always be detected, but
-         * Resume-Detect interrupts may be prohibited.  (In the absence
-         * of CONFIG_PM, they are always disallowed.)
+        /*
+         * In auto-stop mode, we must be able to detect new connections.
+         * The user can force us to poll by disabling remote wakeup;
+         * otherwise we will use the EGSM/RD mechanism.
          */
         if (auto_stop) {
                 if (!device_may_wakeup(&rhdev->dev))
-                        int_enable = 0;
+                        egsm_enable = int_enable = 0;
+        }
 
-        /* In bus-suspend mode wakeups may be disabled, but if they are
-         * allowed then so are Resume-Detect interrupts.
-         */
-        } else {
 #ifdef CONFIG_PM
+        /*
+         * In bus-suspend mode, we use the wakeup setting specified
+         * for the root hub.
+         */
+        else {
                 if (!rhdev->do_remote_wakeup)
                         wakeup_enable = 0;
-#endif
         }
+#endif
 
-        /* EGSM causes the root hub to echo a 'K' signal (resume) out any
-         * port which requests a remote wakeup.  According to the USB spec,
-         * every hub is supposed to do this.  But if we are ignoring
-         * remote-wakeup requests anyway then there's no point to it.
-         * We also shouldn't enable EGSM if it's broken.
-         */
-        if (!wakeup_enable || global_suspend_mode_is_broken(uhci))
-                egsm_enable = 0;
-
-        /* If we're ignoring wakeup events then there's no reason to
-         * enable Resume-Detect interrupts.  We also shouldn't enable
-         * them if they are broken or disallowed.
+        /*
+         * UHCI doesn't distinguish between wakeup requests from downstream
+         * devices and local connect/disconnect events.  There's no way to
+         * enable one without the other; both are controlled by EGSM.  Thus
+         * if wakeups are disallowed then EGSM must be turned off -- in which
+         * case remote wakeup requests from downstream during system sleep
+         * will be lost.
+         *
+         * In addition, if EGSM is broken then we can't use it.  Likewise,
+         * if Resume-Detect interrupts are broken then we can't use them.
          *
-         * This logic may lead us to enabling RD but not EGSM.  The UHCI
-         * spec foolishly says that RD works only when EGSM is on, but
-         * there's no harm in enabling it anyway -- perhaps some chips
-         * will implement it!
+         * Finally, neither EGSM nor RD is useful by itself.  Without EGSM,
+         * the RD status bit will never get set.  Without RD, the controller
+         * won't generate interrupts to tell the system about wakeup events.
          */
-        if (!wakeup_enable || resume_detect_interrupts_are_broken(uhci) ||
-                        !int_enable)
-                uhci->RD_enable = int_enable = 0;
+        if (!wakeup_enable || global_suspend_mode_is_broken(uhci) ||
+                        resume_detect_interrupts_are_broken(uhci))
+                egsm_enable = int_enable = 0;
 
+        uhci->RD_enable = !!int_enable;
         uhci_writew(uhci, int_enable, USBINTR);
         uhci_writew(uhci, egsm_enable | USBCMD_CF, USBCMD);
         mb();
@@ -364,10 +364,12 @@ __acquires(uhci->lock)
         uhci->rh_state = new_state;
         uhci->is_stopped = UHCI_IS_STOPPED;
 
-        /* If interrupts don't work and remote wakeup is enabled then
-         * the suspended root hub needs to be polled.
+        /*
+         * If remote wakeup is enabled but either EGSM or RD interrupts
+         * doesn't work, then we won't get an interrupt when a wakeup event
+         * occurs.  Thus the suspended root hub needs to be polled.
          */
-        if (!int_enable && wakeup_enable)
+        if (wakeup_enable && (!int_enable || !egsm_enable))
                 set_bit(HCD_FLAG_POLL_RH, &uhci_to_hcd(uhci)->flags);
         else
                 clear_bit(HCD_FLAG_POLL_RH, &uhci_to_hcd(uhci)->flags);