[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 <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 121 insertions, 86 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 0da2373..1180c15 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -519,119 +519,120 @@ error:
 /*-------------------------------------------------------------------------*/
 
 /*
- * 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().
  */
+void usb_hcd_poll_rh_status(struct usb_hcd *hcd)
+{
+	struct urb	*urb;
+	int		length;
+	unsigned long	flags;
+	char		buffer[4];	/* Any root hubs with > 31 ports? */
 
-static void rh_report_status (unsigned long ptr);
+	if (!hcd->uses_new_polling && !hcd->status_urb)
+		return;
 
-static int rh_status_urb (struct usb_hcd *hcd, struct urb *urb) 
-{
-	int	len = 1 + (urb->dev->maxchild / 8);
+	length = hcd->driver->hub_status_data(hcd, buffer);
+	if (length > 0) {
 
-	/* 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;
+		/* 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
+			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);
+		else
+			hcd->poll_pending = 1;
+		local_irq_restore (flags);
 	}
 
-	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;
+	/* 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 void rh_report_status (unsigned long ptr)
+static int rh_queue_status (struct usb_hcd *hcd, struct urb *urb)
 {
-	struct urb	*urb;
-	struct usb_hcd	*hcd;
-	int		length = 0;
+	int		retval;
 	unsigned long	flags;
+	int		len = 1 + (urb->dev->maxchild / 8);
 
-	urb = (struct urb *) ptr;
-	local_irq_save (flags);
-	spin_lock (&urb->lock);
+	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 */
 
-	/* 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);
-		return;
-	}
+		if (!hcd->uses_new_polling)
+			mod_timer (&hcd->rh_timer, jiffies +
+					msecs_to_jiffies(250));
 
-	/* 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;
-		} else
-			mod_timer (&hcd->rh_timer, jiffies + HZ/4);
+		/* 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 (&hcd_data_lock);
-	spin_unlock (&urb->lock);
-
-	/* local irqs are always blocked in completions */
-	if (length > 0)
-		usb_hcd_giveback_urb (hcd, urb, NULL);
-	local_irq_restore (flags);
+	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;
-
-	/* 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);
+	if (usb_pipeendpoint(urb->pipe) == 0) {	/* Control URB */
+		if (in_interrupt())
+			return 0;		/* nothing to do */
 
-	} else if (usb_pipeendpoint(urb->pipe) == 0) {
 		spin_lock_irq(&urb->lock);	/* from usb_kill_urb */
 		++urb->reject;
 		spin_unlock_irq(&urb->lock);
@@ -642,8 +643,22 @@ static int usb_rh_urb_dequeue (struct usb_hcd *hcd, struct urb *urb)
 		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;
 }
@@ -885,6 +900,16 @@ int usb_hcd_register_root_hub (struct usb_device *usb_dev, struct usb_hcd *hcd)
 }
 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);
+}
+
 
 /*-------------------------------------------------------------------------*/
 
@@ -1348,7 +1373,8 @@ hcd_endpoint_disable (struct usb_device *udev, struct usb_host_endpoint *ep)
 
 	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 ();
 
@@ -1612,6 +1638,8 @@ void usb_hc_died (struct usb_hcd *hcd)
 
 	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,
@@ -1665,6 +1693,8 @@ struct usb_hcd *usb_create_hcd (const struct hc_driver *driver,
 	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 :
@@ -1748,6 +1778,8 @@ int usb_add_hcd(struct usb_hcd *hcd,
 		goto err3;
 	}
 
+	if (hcd->uses_new_polling && hcd->poll_rh)
+		usb_hcd_poll_rh_status(hcd);
 	return retval;
 
  err3:
@@ -1782,6 +1814,9 @@ void usb_remove_hcd(struct usb_hcd *hcd)
 	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;