OHCI: Allow broken controllers to auto-stop

This patch (as1134) attempts to improve the way we handle OHCI
controllers with broken Root Hub Status Change interrupt support. In
these controllers the RHSC interrupt bit essentially never turns off,
making RHSC interrupts useless -- they have to remain permanently
disabled.

Such controllers should still be allowed to turn off their root hubs
when no devices are attached. Polling for new connections can
continue while the root hub is suspended. The patch implements this
feature. (It won't have much effect unless CONFIG_PM is enabled and
CONFIG_USB_SUSPEND is disabled, but since the overhead is very small
we may as well do it.)

Signed-off-by: Alan Stern <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/ohci-hub.c

···
 		int any_connected)
 {
 	int	poll_rh = 1;
-	int	rhsc;
+	int	rhsc_status, rhsc_enable;
 
-	rhsc = ohci_readl(ohci, &ohci->regs->intrenable) & OHCI_INTR_RHSC;
+	/* Some broken controllers never turn off RHCS in the interrupt
+	 * status register.  For their sake we won't re-enable RHSC
+	 * interrupts if the interrupt bit is already active.
+	 */
+	rhsc_status = ohci_readl(ohci, &ohci->regs->intrstatus) &
+			OHCI_INTR_RHSC;
+	rhsc_enable = ohci_readl(ohci, &ohci->regs->intrenable) &
+			OHCI_INTR_RHSC;
+
 	switch (ohci->hc_control & OHCI_CTRL_HCFS) {
-
 	case OHCI_USB_OPER:
-		/* If no status changes are pending, enable status-change
-		 * interrupts.
-		 */
-		if (!rhsc && !changed) {
-			rhsc = OHCI_INTR_RHSC;
-			ohci_writel(ohci, rhsc, &ohci->regs->intrenable);
+		/* If no status changes are pending, enable RHSC interrupts. */
+		if (!rhsc_enable && !rhsc_status && !changed) {
+			rhsc_enable = OHCI_INTR_RHSC;
+			ohci_writel(ohci, rhsc_enable, &ohci->regs->intrenable);
 		}
 
 		/* Keep on polling until we know a device is connected
···
 			if (any_connected ||
 					!device_may_wakeup(&ohci_to_hcd(ohci)
 						->self.root_hub->dev)) {
-				if (rhsc)
+				if (rhsc_enable)
 					poll_rh = 0;
 			} else {
 				ohci->autostop = 1;
···
 				ohci->autostop = 0;
 				ohci->next_statechange = jiffies +
 						STATECHANGE_DELAY;
-			} else if (rhsc && time_after_eq(jiffies,
+			} else if (time_after_eq(jiffies,
 						ohci->next_statechange)
 					&& !ohci->ed_rm_list
 					&& !(ohci->hc_control &
 						OHCI_SCHED_ENABLES)) {
 				ohci_rh_suspend(ohci, 1);
-				poll_rh = 0;
+				if (rhsc_enable)
+					poll_rh = 0;
 			}
 		}
 		break;
 
-	/* if there is a port change, autostart or ask to be resumed */
 	case OHCI_USB_SUSPEND:
 	case OHCI_USB_RESUME:
+		/* if there is a port change, autostart or ask to be resumed */
 		if (changed) {
 			if (ohci->autostop)
 				ohci_rh_resume(ohci);
 			else
 				usb_hcd_resume_root_hub(ohci_to_hcd(ohci));
 		} else {
-			if (!rhsc && (ohci->autostop ||
+			if (!rhsc_enable && !rhsc_status && (ohci->autostop ||
 					ohci_to_hcd(ohci)->self.root_hub->
-						do_remote_wakeup))
-				ohci_writel(ohci, OHCI_INTR_RHSC,
+						do_remote_wakeup)) {
+				rhsc_enable = OHCI_INTR_RHSC;
+				ohci_writel(ohci, rhsc_enable,
 						&ohci->regs->intrenable);
-
-			/* everything is idle, no need for polling */
-			poll_rh = 0;
+			}
+			if (rhsc_enable)
+				poll_rh = 0;
 		}
 		break;
 	}
···
 static int ohci_root_hub_state_changes(struct ohci_hcd *ohci, int changed,
 		int any_connected)
 {
+	int	rhsc_status;
+
 	/* If RHSC is enabled, don't poll */
 	if (ohci_readl(ohci, &ohci->regs->intrenable) & OHCI_INTR_RHSC)
 		return 0;
 
-	/* If no status changes are pending, enable status-change interrupts */
-	if (!changed) {
+	/* If no status changes are pending, enable RHSC interrupts */
+	rhsc_status = ohci_readl(ohci, &ohci->regs->intrstatus) &
+			OHCI_INTR_RHSC;
+	if (!changed && !rhsc_status) {
 		ohci_writel(ohci, OHCI_INTR_RHSC, &ohci->regs->intrenable);
 		return 0;
 	}
···
 		buf [1] = 0;
 		length++;
 	}
-
-	/* Some broken controllers never turn off RHCS in the interrupt
-	 * status register.  For their sake we won't re-enable RHSC
-	 * interrupts if the flag is already set.
-	 */
-	if (ohci_readl(ohci, &ohci->regs->intrstatus) & OHCI_INTR_RHSC)
-		changed = 1;
 
 	/* look at each port */
 	for (i = 0; i < ohci->num_ports; i++) {