USB: improve port transitions when EHCI starts up

It seems to be getting more common recently for EHCI host controllers
to be probed after their companion UHCI or OHCI controllers. This may
be caused partly by splitting the ehci-pci driver out from ehci-hcd,
or it may be caused by changes in the way the kernel does driver
probing.

Regardless, it has a tendency to cause problems. When an EHCI
controller is initialized, it takes ownership of all the ports away
from the companions. In effect, it forcefully disconnects all the USB
devices that may already be using a companion controller.

This patch (as1672b) tries to make the transition more orderly by
deconfiguring the root hubs for all the companion controllers before
initializing the EHCI controller, and reconfiguring them afterward.
The result is a soft disconnect rather than a hard one.

Internally, the patch refactors the code involved in associating EHCI
controllers with their companions. The old approach, in which a
single function is called with an argument telling it what to do (the
companion_action enum), has been replaced with a scheme using multiple
callback functions, each performing a single task.

This patch won't solve all the problems people encounter when their
EHCI controllers start up, but it will at least reduce the number of
error messages generated by the unexpected disconnections.

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

drivers/usb/core/hcd-pci.c

···
 
 /* PCI-based HCs are common, but plenty of non-PCI HCs are used too */
 
-#ifdef CONFIG_PM_SLEEP
-
-/* Coordinate handoffs between EHCI and companion controllers
- * during system resume
+/*
+ * Coordinate handoffs between EHCI and companion controllers
+ * during EHCI probing and system resume.
  */
 
-static DEFINE_MUTEX(companions_mutex);
+static DECLARE_RWSEM(companions_rwsem);
 
 #define CL_UHCI		PCI_CLASS_SERIAL_USB_UHCI
 #define CL_OHCI		PCI_CLASS_SERIAL_USB_OHCI
 #define CL_EHCI		PCI_CLASS_SERIAL_USB_EHCI
 
-enum companion_action {
-	SET_HS_COMPANION, CLEAR_HS_COMPANION, WAIT_FOR_COMPANIONS
-};
+static inline int is_ohci_or_uhci(struct pci_dev *pdev)
+{
+	return pdev->class == CL_OHCI || pdev->class == CL_UHCI;
+}
 
-static void companion_common(struct pci_dev *pdev, struct usb_hcd *hcd,
-		enum companion_action action)
+typedef void (*companion_fn)(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd);
+
+/* Iterate over PCI devices in the same slot as pdev and call fn for each */
+static void for_each_companion(struct pci_dev *pdev, struct usb_hcd *hcd,
+		companion_fn fn)
 {
 	struct pci_dev		*companion;
 	struct usb_hcd		*companion_hcd;
 	unsigned int		slot = PCI_SLOT(pdev->devfn);
 
-	/* Iterate through other PCI functions in the same slot.
-	 * If pdev is OHCI or UHCI then we are looking for EHCI, and
-	 * vice versa.
+	/*
+	 * Iterate through other PCI functions in the same slot.
+	 * If the function's drvdata isn't set then it isn't bound to
+	 * a USB host controller driver, so skip it.
 	 */
 	companion = NULL;
 	for_each_pci_dev(companion) {
 		if (companion->bus != pdev->bus ||
 				PCI_SLOT(companion->devfn) != slot)
 			continue;
-
 		companion_hcd = pci_get_drvdata(companion);
 		if (!companion_hcd)
 			continue;
-
-		/* For SET_HS_COMPANION, store a pointer to the EHCI bus in
-		 * the OHCI/UHCI companion bus structure.
-		 * For CLEAR_HS_COMPANION, clear the pointer to the EHCI bus
-		 * in the OHCI/UHCI companion bus structure.
-		 * For WAIT_FOR_COMPANIONS, wait until the OHCI/UHCI
-		 * companion controllers have fully resumed.
-		 */
-
-		if ((pdev->class == CL_OHCI || pdev->class == CL_UHCI) &&
-				companion->class == CL_EHCI) {
-			/* action must be SET_HS_COMPANION */
-			dev_dbg(&companion->dev, "HS companion for %s\n",
-					dev_name(&pdev->dev));
-			hcd->self.hs_companion = &companion_hcd->self;
-
-		} else if (pdev->class == CL_EHCI &&
-				(companion->class == CL_OHCI ||
-				companion->class == CL_UHCI)) {
-			switch (action) {
-			case SET_HS_COMPANION:
-				dev_dbg(&pdev->dev, "HS companion for %s\n",
-						dev_name(&companion->dev));
-				companion_hcd->self.hs_companion = &hcd->self;
-				break;
-			case CLEAR_HS_COMPANION:
-				companion_hcd->self.hs_companion = NULL;
-				break;
-			case WAIT_FOR_COMPANIONS:
-				device_pm_wait_for_dev(&pdev->dev,
-						&companion->dev);
-				break;
-			}
-		}
+		fn(pdev, hcd, companion, companion_hcd);
 	}
 }
 
-static void set_hs_companion(struct pci_dev *pdev, struct usb_hcd *hcd)
+/*
+ * We're about to add an EHCI controller, which will unceremoniously grab
+ * all the port connections away from its companions.  To prevent annoying
+ * error messages, lock the companion's root hub and gracefully unconfigure
+ * it beforehand.  Leave it locked until the EHCI controller is all set.
+ */
+static void ehci_pre_add(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd)
 {
-	mutex_lock(&companions_mutex);
-	dev_set_drvdata(&pdev->dev, hcd);
-	companion_common(pdev, hcd, SET_HS_COMPANION);
-	mutex_unlock(&companions_mutex);
+	struct usb_device *udev;
+
+	if (is_ohci_or_uhci(companion)) {
+		udev = companion_hcd->self.root_hub;
+		usb_lock_device(udev);
+		usb_set_configuration(udev, 0);
+	}
 }
 
-static void clear_hs_companion(struct pci_dev *pdev, struct usb_hcd *hcd)
+/*
+ * Adding the EHCI controller has either succeeded or failed.  Set the
+ * companion pointer accordingly, and in either case, reconfigure and
+ * unlock the root hub.
+ */
+static void ehci_post_add(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd)
 {
-	mutex_lock(&companions_mutex);
-	dev_set_drvdata(&pdev->dev, NULL);
+	struct usb_device *udev;
 
-	/* If pdev is OHCI or UHCI, just clear its hs_companion pointer */
-	if (pdev->class == CL_OHCI || pdev->class == CL_UHCI)
-		hcd->self.hs_companion = NULL;
-
-	/* Otherwise search for companion buses and clear their pointers */
-	else
-		companion_common(pdev, hcd, CLEAR_HS_COMPANION);
-	mutex_unlock(&companions_mutex);
+	if (is_ohci_or_uhci(companion)) {
+		if (dev_get_drvdata(&pdev->dev)) {	/* Succeeded */
+			dev_dbg(&pdev->dev, "HS companion for %s\n",
+					dev_name(&companion->dev));
+			companion_hcd->self.hs_companion = &hcd->self;
+		}
+		udev = companion_hcd->self.root_hub;
+		usb_set_configuration(udev, 1);
+		usb_unlock_device(udev);
+	}
 }
 
-static void wait_for_companions(struct pci_dev *pdev, struct usb_hcd *hcd)
+/*
+ * We just added a non-EHCI controller.  Find the EHCI controller to
+ * which it is a companion, and store a pointer to the bus structure.
+ */
+static void non_ehci_add(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd)
 {
-	/* Only EHCI controllers need to wait.
-	 * No locking is needed because a controller cannot be resumed
-	 * while one of its companions is getting unbound.
-	 */
-	if (pdev->class == CL_EHCI)
-		companion_common(pdev, hcd, WAIT_FOR_COMPANIONS);
+	if (is_ohci_or_uhci(pdev) && companion->class == CL_EHCI) {
+		dev_dbg(&pdev->dev, "FS/LS companion for %s\n",
+				dev_name(&companion->dev));
+		hcd->self.hs_companion = &companion_hcd->self;
+	}
 }
 
-#else /* !CONFIG_PM_SLEEP */
+/* We are removing an EHCI controller.  Clear the companions' pointers. */
+static void ehci_remove(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd)
+{
+	if (is_ohci_or_uhci(companion))
+		companion_hcd->self.hs_companion = NULL;
+}
 
-static inline void set_hs_companion(struct pci_dev *d, struct usb_hcd *h) {}
-static inline void clear_hs_companion(struct pci_dev *d, struct usb_hcd *h) {}
-static inline void wait_for_companions(struct pci_dev *d, struct usb_hcd *h) {}
+#ifdef	CONFIG_PM
 
-#endif /* !CONFIG_PM_SLEEP */
+/* An EHCI controller must wait for its companions before resuming. */
+static void ehci_wait_for_companions(struct pci_dev *pdev, struct usb_hcd *hcd,
+		struct pci_dev *companion, struct usb_hcd *companion_hcd)
+{
+	if (is_ohci_or_uhci(companion))
+		device_pm_wait_for_dev(&pdev->dev, &companion->dev);
+}
+
+#endif	/* CONFIG_PM */
 
 /*-------------------------------------------------------------------------*/
 
···
 				driver->description)) {
 			dev_dbg(&dev->dev, "controller already in use\n");
 			retval = -EBUSY;
-			goto clear_companion;
+			goto put_hcd;
 		}
 		hcd->regs = ioremap_nocache(hcd->rsrc_start, hcd->rsrc_len);
 		if (hcd->regs == NULL) {
···
 		if (region == PCI_ROM_RESOURCE) {
 			dev_dbg(&dev->dev, "no i/o regions available\n");
 			retval = -EBUSY;
-			goto clear_companion;
+			goto put_hcd;
 		}
 	}
 
 	pci_set_master(dev);
 
-	retval = usb_add_hcd(hcd, hcd_irq, IRQF_SHARED);
+	/* Note: dev_set_drvdata must be called while holding the rwsem */
+	if (dev->class == CL_EHCI) {
+		down_write(&companions_rwsem);
+		dev_set_drvdata(&dev->dev, hcd);
+		for_each_companion(dev, hcd, ehci_pre_add);
+		retval = usb_add_hcd(hcd, hcd_irq, IRQF_SHARED);
+		if (retval != 0)
+			dev_set_drvdata(&dev->dev, NULL);
+		for_each_companion(dev, hcd, ehci_post_add);
+		up_write(&companions_rwsem);
+	} else {
+		down_read(&companions_rwsem);
+		dev_set_drvdata(&dev->dev, hcd);
+		retval = usb_add_hcd(hcd, hcd_irq, IRQF_SHARED);
+		if (retval != 0)
+			dev_set_drvdata(&dev->dev, NULL);
+		else
+			for_each_companion(dev, hcd, non_ehci_add);
+		up_read(&companions_rwsem);
+	}
+
 	if (retval != 0)
 		goto unmap_registers;
-	set_hs_companion(dev, hcd);
 
 	if (pci_dev_run_wake(dev))
 		pm_runtime_put_noidle(&dev->dev);
···
 		release_mem_region(hcd->rsrc_start, hcd->rsrc_len);
 	} else
 		release_region(hcd->rsrc_start, hcd->rsrc_len);
-clear_companion:
-	clear_hs_companion(dev, hcd);
+put_hcd:
 	usb_put_hcd(hcd);
 disable_pci:
 	pci_disable_device(dev);
···
 	usb_hcd_irq(0, hcd);
 	local_irq_enable();
 
-	usb_remove_hcd(hcd);
+	/* Note: dev_set_drvdata must be called while holding the rwsem */
+	if (dev->class == CL_EHCI) {
+		down_write(&companions_rwsem);
+		for_each_companion(dev, hcd, ehci_remove);
+		usb_remove_hcd(hcd);
+		dev_set_drvdata(&dev->dev, NULL);
+		up_write(&companions_rwsem);
+	} else {
+		/* Not EHCI; just clear the companion pointer */
+		down_read(&companions_rwsem);
+		hcd->self.hs_companion = NULL;
+		usb_remove_hcd(hcd);
+		dev_set_drvdata(&dev->dev, NULL);
+		up_read(&companions_rwsem);
+	}
+
 	if (hcd->driver->flags & HCD_MEMORY) {
 		iounmap(hcd->regs);
 		release_mem_region(hcd->rsrc_start, hcd->rsrc_len);
 	} else {
 		release_region(hcd->rsrc_start, hcd->rsrc_len);
 	}
-	clear_hs_companion(dev, hcd);
+
 	usb_put_hcd(hcd);
 	pci_disable_device(dev);
 }
···
 	pci_set_master(pci_dev);
 
 	if (hcd->driver->pci_resume && !HCD_DEAD(hcd)) {
-		if (event != PM_EVENT_AUTO_RESUME)
-			wait_for_companions(pci_dev, hcd);
+
+		/*
+		 * Only EHCI controllers have to wait for their companions.
+		 * No locking is needed because PCI controller drivers do not
+		 * get unbound during system resume.
+		 */
+		if (pci_dev->class == CL_EHCI && event != PM_EVENT_AUTO_RESUME)
+			for_each_companion(pci_dev, hcd,
+					ehci_wait_for_companions);
 
 		retval = hcd->driver->pci_resume(hcd,
 				event == PM_EVENT_RESTORE);