USB: OHCI avoids root hub timer polling

This teaches OHCI to use the root hub status change (RHSC) IRQ, bypassing
root hub timers most of the time and switching over to the "new" root hub
polling scheme.  It's complicated by the fact that implementations of OHCI
trigger and ack that IRQ differently (the spec is vague there).

Avoiding root hub timers helps mechanisms like "dynamic tick" leave the
CPU in lowpower modes for longer intervals.

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

1 files changed, 46 insertions, 21 deletions

diff --git a/drivers/usb/host/ohci-hub.c b/drivers/usb/host/ohci-hub.c
index 5b0a23fd798b..f1b1ed086bde 100644
--- a/drivers/usb/host/ohci-hub.c
+++ b/drivers/usb/host/ohci-hub.c
@@ -36,6 +36,14 @@
 
 /*-------------------------------------------------------------------------*/
 
+/* hcd->hub_irq_enable() */
+static void ohci_rhsc_enable (struct usb_hcd *hcd)
+{
+	struct ohci_hcd		*ohci = hcd_to_ohci (hcd);
+
+	ohci_writel (ohci, OHCI_INTR_RHSC, &ohci->regs->intrenable);
+}
+
 #ifdef	CONFIG_PM
 
 #define OHCI_SCHED_ENABLES \
@@ -123,6 +131,9 @@ static int ohci_bus_suspend (struct usb_hcd *hcd)
 	/* no resumes until devices finish suspending */
 	ohci->next_statechange = jiffies + msecs_to_jiffies (5);
 
+	/* no timer polling */
+	hcd->poll_rh = 0;
+
 done:
 	/* external suspend vs self autosuspend ... same effect */
 	if (status == 0)
@@ -256,8 +267,8 @@ static int ohci_bus_resume (struct usb_hcd *hcd)
 	/* TRSMRCY */
 	msleep (10);
 
-	/* keep it alive for ~5x suspend + resume costs */
-	ohci->next_statechange = jiffies + msecs_to_jiffies (250);
+	/* keep it alive for more than ~5x suspend + resume costs */
+	ohci->next_statechange = jiffies + STATECHANGE_DELAY;
 
 	/* maybe turn schedules back on */
 	enables = 0;
@@ -302,9 +313,10 @@ ohci_hub_status_data (struct usb_hcd *hcd, char *buf)
 {
 	struct ohci_hcd	*ohci = hcd_to_ohci (hcd);
 	int		i, changed = 0, length = 1;
-	int		can_suspend = device_may_wakeup(&hcd->self.root_hub->dev);
+	int		can_suspend;
 	unsigned long	flags;
 
+	can_suspend = device_may_wakeup(&hcd->self.root_hub->dev);
 	spin_lock_irqsave (&ohci->lock, flags);
 
 	/* handle autosuspended root:  finish resuming before
@@ -339,6 +351,10 @@ ohci_hub_status_data (struct usb_hcd *hcd, char *buf)
 	for (i = 0; i < ohci->num_ports; i++) {
 		u32	status = roothub_portstatus (ohci, i);
 
+		/* can't autosuspend with active ports */
+		if ((status & RH_PS_PES) && !(status & RH_PS_PSS))
+			can_suspend = 0;
+
 		if (status & (RH_PS_CSC | RH_PS_PESC | RH_PS_PSSC
 				| RH_PS_OCIC | RH_PS_PRSC)) {
 			changed = 1;
@@ -348,32 +364,41 @@ ohci_hub_status_data (struct usb_hcd *hcd, char *buf)
 			    buf [1] |= 1 << (i - 7);
 			continue;
 		}
+	}
 
-		/* can suspend if no ports are enabled; or if all all
-		 * enabled ports are suspended AND remote wakeup is on.
-		 */
-		if (!(status & RH_PS_CCS))
-			continue;
-		if ((status & RH_PS_PSS) && can_suspend)
-			continue;
+	/* after root hub changes, stop polling after debouncing
+	 * for a while and maybe kicking in autosuspend
+	 */
+	if (changed) {
+		ohci->next_statechange = jiffies + STATECHANGE_DELAY;
 		can_suspend = 0;
+	} else if (time_before (jiffies, ohci->next_statechange)) {
+		can_suspend = 0;
+	} else {
+#ifdef	CONFIG_PM
+		can_suspend = can_suspend
+			&& !ohci->ed_rm_list
+			&& ((OHCI_CTRL_HCFS | OHCI_SCHED_ENABLES)
+					& ohci->hc_control)
+				== OHCI_USB_OPER;
+#endif
+		if (hcd->uses_new_polling) {
+			hcd->poll_rh = 0;
+			/* use INTR_RHSC iff INTR_RD won't apply */
+			if (!can_suspend)
+				ohci_writel (ohci, OHCI_INTR_RHSC,
+						&ohci->regs->intrenable);
+		}
 	}
+
 done:
 	spin_unlock_irqrestore (&ohci->lock, flags);
 
-#ifdef CONFIG_PM
-	/* save power by suspending idle root hubs;
+#ifdef	CONFIG_PM
+	/* save power by autosuspending idle root hubs;
 	 * INTR_RD wakes us when there's work
 	 */
-	if (can_suspend
-			&& !changed
-			&& !ohci->ed_rm_list
-			&& ((OHCI_CTRL_HCFS | OHCI_SCHED_ENABLES)
-					& ohci->hc_control)
-				== OHCI_USB_OPER
-			&& time_after (jiffies, ohci->next_statechange)
-			&& usb_trylock_device (hcd->self.root_hub) == 0
-			) {
+	if (can_suspend && usb_trylock_device (hcd->self.root_hub) == 0) {
 		ohci_vdbg (ohci, "autosuspend\n");
 		(void) ohci_bus_suspend (hcd);
 		usb_unlock_device (hcd->self.root_hub);