[PATCH] usbcore support for root-hub IRQ instead of polling

This is a revised version of an earlier patch to add support to usbcore
for driving root hubs by interrupts rather than polling.

There's a temporary flag added to struct usb_hcd, marking devices whose
drivers are aware of the new mechanism. By default that flag doesn't get
set so drivers will continue to see the same polling behavior as before.
This way we can convert the HCDs one by one to use interrupt-based event
reporting, and the temporary flag can be removed when they're all done.

Also included is a small change to the hcd_disable_endpoint routine.
Although endpoints normally shouldn't be disabled while a controller is
suspended, it's legal to do so when the controller's driver is being
rmmod'ed.

Lastly the patch adds a new callback, .hub_irq_enable, for use by HCDs
where the root hub's port-change interrupts are level-triggered rather
than edge-triggered. The callback is invoked each time khubd has finished
processing a root hub, to let the HCD know that the interrupt can safely
be re-enabled.

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

drivers/usb/core/hcd.c

···
 /*-------------------------------------------------------------------------*/
 
 /*
- * Root Hub interrupt transfers are synthesized with a timer.
- * Completions are called in_interrupt() but not in_irq().
+ * Root Hub interrupt transfers are polled using a timer if the
+ * driver requests it; otherwise the driver is responsible for
+ * calling usb_hcd_poll_rh_status() when an event occurs.
  *
- * Note: some root hubs (including common UHCI based designs) can't
- * correctly issue port change IRQs.  They're the ones that _need_ a
- * timer; most other root hubs don't.  Some systems could save a
- * lot of battery power by eliminating these root hub timer IRQs.
+ * Completions are called in_interrupt(), but they may or may not
+ * be in_irq().
  */
-
-static void rh_report_status (unsigned long ptr);
-
-static int rh_status_urb (struct usb_hcd *hcd, struct urb *urb) 
-{
-	int	len = 1 + (urb->dev->maxchild / 8);
-
-	/* rh_timer protected by hcd_data_lock */
-	if (hcd->rh_timer.data || urb->transfer_buffer_length < len) {
-		dev_dbg (hcd->self.controller,
-				"not queuing rh status urb, stat %d\n",
-				urb->status);
-		return -EINVAL;
-	}
-
-	init_timer (&hcd->rh_timer);
-	hcd->rh_timer.function = rh_report_status;
-	hcd->rh_timer.data = (unsigned long) urb;
-	/* USB 2.0 spec says 256msec; this is close enough */
-	hcd->rh_timer.expires = jiffies + HZ/4;
-	add_timer (&hcd->rh_timer);
-	urb->hcpriv = hcd;	/* nonzero to indicate it's queued */
-	return 0;
-}
-
-/* timer callback */
-
-static void rh_report_status (unsigned long ptr)
+void usb_hcd_poll_rh_status(struct usb_hcd *hcd)
 {
 	struct urb	*urb;
-	struct usb_hcd	*hcd;
-	int		length = 0;
+	int		length;
 	unsigned long	flags;
+	char		buffer[4];	/* Any root hubs with > 31 ports? */
 
-	urb = (struct urb *) ptr;
-	local_irq_save (flags);
-	spin_lock (&urb->lock);
-
-	/* do nothing if the urb's been unlinked */
-	if (!urb->dev
-			|| urb->status != -EINPROGRESS
-			|| (hcd = urb->dev->bus->hcpriv) == NULL) {
-		spin_unlock (&urb->lock);
-		local_irq_restore (flags);
+	if (!hcd->uses_new_polling && !hcd->status_urb)
 		return;
-	}
 
-	/* complete the status urb, or retrigger the timer */
-	spin_lock (&hcd_data_lock);
-	if (urb->dev->state == USB_STATE_CONFIGURED) {
-		length = hcd->driver->hub_status_data (
-					hcd, urb->transfer_buffer);
-		if (length > 0) {
-			hcd->rh_timer.data = 0;
-			urb->actual_length = length;
-			urb->status = 0;
-			urb->hcpriv = NULL;
+	length = hcd->driver->hub_status_data(hcd, buffer);
+	if (length > 0) {
+
+		/* try to complete the status urb */
+		local_irq_save (flags);
+		spin_lock(&hcd_root_hub_lock);
+		urb = hcd->status_urb;
+		if (urb) {
+			spin_lock(&urb->lock);
+			if (urb->status == -EINPROGRESS) {
+				hcd->poll_pending = 0;
+				hcd->status_urb = NULL;
+				urb->status = 0;
+				urb->hcpriv = NULL;
+				urb->actual_length = length;
+				memcpy(urb->transfer_buffer, buffer, length);
+			} else		/* urb has been unlinked */
+				length = 0;
+			spin_unlock(&urb->lock);
 		} else
-			mod_timer (&hcd->rh_timer, jiffies + HZ/4);
-	}
-	spin_unlock (&hcd_data_lock);
-	spin_unlock (&urb->lock);
+			length = 0;
+		spin_unlock(&hcd_root_hub_lock);
 
-	/* local irqs are always blocked in completions */
-	if (length > 0)
-		usb_hcd_giveback_urb (hcd, urb, NULL);
-	local_irq_restore (flags);
+		/* local irqs are always blocked in completions */
+		if (length > 0)
+			usb_hcd_giveback_urb (hcd, urb, NULL);
+		else
+			hcd->poll_pending = 1;
+		local_irq_restore (flags);
+	}
+
+	/* The USB 2.0 spec says 256 ms.  This is close enough and won't
+	 * exceed that limit if HZ is 100. */
+	if (hcd->uses_new_polling ? hcd->poll_rh :
+			(length == 0 && hcd->status_urb != NULL))
+		mod_timer (&hcd->rh_timer, jiffies + msecs_to_jiffies(250));
+}
+EXPORT_SYMBOL_GPL(usb_hcd_poll_rh_status);
+
+/* timer callback */
+static void rh_timer_func (unsigned long _hcd)
+{
+	usb_hcd_poll_rh_status((struct usb_hcd *) _hcd);
 }
 
 /*-------------------------------------------------------------------------*/
+
+static int rh_queue_status (struct usb_hcd *hcd, struct urb *urb)
+{
+	int		retval;
+	unsigned long	flags;
+	int		len = 1 + (urb->dev->maxchild / 8);
+
+	spin_lock_irqsave (&hcd_root_hub_lock, flags);
+	if (urb->status != -EINPROGRESS)	/* already unlinked */
+		retval = urb->status;
+	else if (hcd->status_urb || urb->transfer_buffer_length < len) {
+		dev_dbg (hcd->self.controller, "not queuing rh status urb\n");
+		retval = -EINVAL;
+	} else {
+		hcd->status_urb = urb;
+		urb->hcpriv = hcd;	/* indicate it's queued */
+
+		if (!hcd->uses_new_polling)
+			mod_timer (&hcd->rh_timer, jiffies +
+					msecs_to_jiffies(250));
+
+		/* If a status change has already occurred, report it ASAP */
+		else if (hcd->poll_pending)
+			mod_timer (&hcd->rh_timer, jiffies);
+		retval = 0;
+	}
+	spin_unlock_irqrestore (&hcd_root_hub_lock, flags);
+	return retval;
+}
 
 static int rh_urb_enqueue (struct usb_hcd *hcd, struct urb *urb)
 {
-	if (usb_pipeint (urb->pipe)) {
-		int		retval;
-		unsigned long	flags;
-
-		spin_lock_irqsave (&hcd_data_lock, flags);
-		retval = rh_status_urb (hcd, urb);
-		spin_unlock_irqrestore (&hcd_data_lock, flags);
-		return retval;
-	}
+	if (usb_pipeint (urb->pipe))
+		return rh_queue_status (hcd, urb);
 	if (usb_pipecontrol (urb->pipe))
 		return rh_call_control (hcd, urb);
-	else
-		return -EINVAL;
+	return -EINVAL;
 }
 
 /*-------------------------------------------------------------------------*/
 
+/* Asynchronous unlinks of root-hub control URBs are legal, but they
+ * don't do anything.  Status URB unlinks must be made in process context
+ * with interrupts enabled.
+ */
 static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
 {
-	unsigned long	flags;
+	if (usb_pipeendpoint(urb->pipe) == 0) {	/* Control URB */
+		if (in_interrupt())
+			return 0;		/* nothing to do */
 
-	/* note:  always a synchronous unlink */
-	if ((unsigned long) urb == hcd->rh_timer.data) {
-		del_timer_sync (&hcd->rh_timer);
-		hcd->rh_timer.data = 0;
-
-		local_irq_save (flags);
-		urb->hcpriv = NULL;
-		usb_hcd_giveback_urb (hcd, urb, NULL);
-		local_irq_restore (flags);
-
-	} else if (usb_pipeendpoint(urb->pipe) == 0) {
 		spin_lock_irq(&urb->lock);	/* from usb_kill_urb */
 		++urb->reject;
 		spin_unlock_irq(&urb->lock);
···
 		spin_lock_irq(&urb->lock);
 		--urb->reject;
 		spin_unlock_irq(&urb->lock);
-	} else
-		return -EINVAL;
+
+	} else {				/* Status URB */
+		if (!hcd->uses_new_polling)
+			del_timer_sync (&hcd->rh_timer);
+		local_irq_disable ();
+		spin_lock (&hcd_root_hub_lock);
+		if (urb == hcd->status_urb) {
+			hcd->status_urb = NULL;
+			urb->hcpriv = NULL;
+		} else
+			urb = NULL;		/* wasn't fully queued */
+		spin_unlock (&hcd_root_hub_lock);
+		if (urb)
+			usb_hcd_giveback_urb (hcd, urb, NULL);
+		local_irq_enable ();
+	}
 
 	return 0;
 }
···
 	return retval;
 }
 EXPORT_SYMBOL_GPL(usb_hcd_register_root_hub);
+
+void usb_enable_root_hub_irq (struct usb_bus *bus)
+{
+	struct usb_hcd *hcd;
+
+	hcd = container_of (bus, struct usb_hcd, self);
+	if (hcd->driver->hub_irq_enable && !hcd->poll_rh &&
+			hcd->state != HC_STATE_HALT)
+		hcd->driver->hub_irq_enable (hcd);
+}
 
 
 /*-------------------------------------------------------------------------*/
···
 
 	hcd = udev->bus->hcpriv;
 
-	WARN_ON (!HC_IS_RUNNING (hcd->state) && hcd->state != HC_STATE_HALT);
+	WARN_ON (!HC_IS_RUNNING (hcd->state) && hcd->state != HC_STATE_HALT &&
+			udev->state != USB_STATE_NOTATTACHED);
 
 	local_irq_disable ();
 
···
 
 	spin_lock_irqsave (&hcd_root_hub_lock, flags);
 	if (hcd->rh_registered) {
+		hcd->poll_rh = 0;
+		del_timer(&hcd->rh_timer);
 
 		/* make khubd clean up old urbs and devices */
 		usb_set_device_state (hcd->self.root_hub,
···
 	hcd->self.bus_name = bus_name;
 
 	init_timer(&hcd->rh_timer);
+	hcd->rh_timer.function = rh_timer_func;
+	hcd->rh_timer.data = (unsigned long) hcd;
 
 	hcd->driver = driver;
 	hcd->product_desc = (driver->product_desc) ? driver->product_desc :
···
 		goto err3;
 	}
 
+	if (hcd->uses_new_polling && hcd->poll_rh)
+		usb_hcd_poll_rh_status(hcd);
 	return retval;
 
  err3:
···
 	hcd->rh_registered = 0;
 	spin_unlock_irq (&hcd_root_hub_lock);
 	usb_disconnect(&hcd->self.root_hub);
+
+	hcd->poll_rh = 0;
+	del_timer_sync(&hcd->rh_timer);
 
 	hcd->driver->stop(hcd);
 	hcd->state = HC_STATE_HALT;

drivers/usb/core/hcd.h

···
 	const char		*product_desc;	/* product/vendor string */
 	char			irq_descr[24];	/* driver + bus # */
 
-	struct timer_list	rh_timer;	/* drives root hub */
+	struct timer_list	rh_timer;	/* drives root-hub polling */
+	struct urb		*status_urb;	/* the current status urb */
 
 	/*
 	 * hardware info/state
···
 	unsigned		can_wakeup:1;	/* hw supports wakeup? */
 	unsigned		remote_wakeup:1;/* sw should use wakeup? */
 	unsigned		rh_registered:1;/* is root hub registered? */
+
+	/* The next flag is a stopgap, to be removed when all the HCDs
+	 * support the new root-hub polling mechanism. */
+	unsigned		uses_new_polling:1;
+	unsigned		poll_rh:1;	/* poll for rh status? */
+	unsigned		poll_pending:1;	/* status has changed? */
 
 	int			irq;		/* irq allocated */
 	void __iomem		*regs;		/* device memory/io */
···
 	int		(*hub_suspend)(struct usb_hcd *);
 	int		(*hub_resume)(struct usb_hcd *);
 	int		(*start_port_reset)(struct usb_hcd *, unsigned port_num);
+	void		(*hub_irq_enable)(struct usb_hcd *);
+		/* Needed only if port-change IRQs are level-triggered */
 };
 
 extern void usb_hcd_giveback_urb (struct usb_hcd *hcd, struct urb *urb, struct pt_regs *regs);
···
 
 /* generic bus glue, needed for host controllers that don't use PCI */
 extern irqreturn_t usb_hcd_irq (int irq, void *__hcd, struct pt_regs *r);
+
 extern void usb_hc_died (struct usb_hcd *hcd);
+extern void usb_hcd_poll_rh_status(struct usb_hcd *hcd);
 
 /* -------------------------------------------------------------------------- */
 
···
 
 extern struct usb_bus *usb_bus_get (struct usb_bus *bus);
 extern void usb_bus_put (struct usb_bus *bus);
+
+extern void usb_enable_root_hub_irq (struct usb_bus *bus);
 
 extern int usb_find_interface_driver (struct usb_device *dev,
 	struct usb_interface *interface);

drivers/usb/core/hub.c

···
 
 		hub->activating = 0;
 
+		/* If this is a root hub, tell the HCD it's okay to
+		 * re-enable port-change interrupts now. */
+		if (!hdev->parent)
+			usb_enable_root_hub_irq(hdev->bus);
+
 loop:
 		usb_unlock_device(hdev);
 		usb_put_intf(intf);