USB: unify reset_resume and normal resume

This patch (as919) unifies the code paths used for normal resume and
for reset-resume.  Earlier I had failed to note a section in the USB
spec which requires the host to resume a suspended port before
resetting it if the attached device is enabled for remote wakeup.
Since the port has to be resumed anyway, we might as well reuse the
existing code.

The main changes are:

	usb_reset_suspended_device() is eliminated.

	usb_root_hub_lost_power() is moved down next to the
	hub_reset_resume() routine, to which it is logically
	related.

	finish_port_resume() does a port reset() if the device's
	reset_resume flag is set.

	usb_port_resume() doesn't check whether the port is initially
	enabled if this is a USB-Persist sort of resume.

	Code to perform the port reset is added to the resume pathway
	for the non-CONFIG_USB_SUSPEND case.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/generic.c

@@ -219,8 +219,6 @@ static int generic_resume(struct usb_device *udev)
 	 */
 	if (!udev->parent)
 		rc = hcd_bus_resume(udev);
-	else if (udev->reset_resume)
-		rc = usb_reset_suspended_device(udev);
 	else
 		rc = usb_port_resume(udev);
 	return rc;

drivers/usb/core/hub.c

@@ -31,6 +31,12 @@
 #include "hcd.h"
 #include "hub.h"
 
+#ifdef	CONFIG_USB_PERSIST
+#define	USB_PERSIST	1
+#else
+#define	USB_PERSIST	0
+#endif
+
 struct usb_hub {
 	struct device		*intfdev;	/* the "interface" device */
 	struct usb_device	*hdev;
@@ -1080,72 +1086,6 @@ void usb_set_device_state(struct usb_device *udev,
 	spin_unlock_irqrestore(&device_state_lock, flags);
 }
 
-
-#ifdef	CONFIG_PM
-
-/**
- * usb_reset_suspended_device - reset a suspended device instead of resuming it
- * @udev: device to be reset instead of resumed
- *
- * If a host controller doesn't maintain VBUS suspend current during a
- * system sleep or is reset when the system wakes up, all the USB
- * power sessions below it will be broken.  This is especially troublesome
- * for mass-storage devices containing mounted filesystems, since the
- * device will appear to have disconnected and all the memory mappings
- * to it will be lost.
- *
- * As an alternative, this routine attempts to recover power sessions for
- * devices that are still present by resetting them instead of resuming
- * them.  If all goes well, the devices will appear to persist across the
- * the interruption of the power sessions.
- *
- * This facility is inherently dangerous.  Although usb_reset_device()
- * makes every effort to insure that the same device is present after the
- * reset as before, it cannot provide a 100% guarantee.  Furthermore it's
- * quite possible for a device to remain unaltered but its media to be
- * changed.  If the user replaces a flash memory card while the system is
- * asleep, he will have only himself to blame when the filesystem on the
- * new card is corrupted and the system crashes.
- */
-int usb_reset_suspended_device(struct usb_device *udev)
-{
-	int rc = 0;
-
-	dev_dbg(&udev->dev, "usb %sresume\n", "reset-");
-
-	/* After we're done the device won't be suspended any more.
-	 * In addition, the reset won't work if udev->state is SUSPENDED.
-	 */
-	usb_set_device_state(udev, udev->actconfig
-			? USB_STATE_CONFIGURED
-			: USB_STATE_ADDRESS);
-
-	/* Root hubs don't need to be (and can't be) reset */
-	if (udev->parent)
-		rc = usb_reset_device(udev);
-	return rc;
-}
-
-/**
- * usb_root_hub_lost_power - called by HCD if the root hub lost Vbus power
- * @rhdev: struct usb_device for the root hub
- *
- * The USB host controller driver calls this function when its root hub
- * is resumed and Vbus power has been interrupted or the controller
- * has been reset.  The routine marks @rhdev as having lost power.  When
- * the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST
- * is enabled then it will carry out power-session recovery, otherwise
- * it will disconnect all the child devices.
- */
-void usb_root_hub_lost_power(struct usb_device *rhdev)
-{
-	dev_warn(&rhdev->dev, "root hub lost power or was reset\n");
-	rhdev->reset_resume = 1;
-}
-EXPORT_SYMBOL_GPL(usb_root_hub_lost_power);
-
-#endif	/* CONFIG_PM */
-
 static void choose_address(struct usb_device *udev)
 {
 	int		devnum;
@@ -1672,18 +1612,22 @@ int usb_port_suspend(struct usb_device *udev)
 /*
  * If the USB "suspend" state is in use (rather than "global suspend"),
  * many devices will be individually taken out of suspend state using
- * special" resume" signaling.  These routines kick in shortly after
+ * special "resume" signaling.  This routine kicks in shortly after
  * hardware resume signaling is finished, either because of selective
  * resume (by host) or remote wakeup (by device) ... now see what changed
  * in the tree that's rooted at this device.
+ *
+ * If @udev->reset_resume is set then the device is reset before the
+ * status check is done.
  */
 static int finish_port_resume(struct usb_device *udev)
 {
-	int	status;
+	int	status = 0;
 	u16	devstatus;
 
 	/* caller owns the udev device lock */
-	dev_dbg(&udev->dev, "finish resume\n");
+	dev_dbg(&udev->dev, "finish %sresume\n",
+			udev->reset_resume ? "reset-" : "");
 
 	/* usb ch9 identifies four variants of SUSPENDED, based on what
 	 * state the device resumes to.  Linux currently won't see the
@@ -1694,13 +1638,23 @@ static int finish_port_resume(struct usb_device *udev)
 			? USB_STATE_CONFIGURED
 			: USB_STATE_ADDRESS);
 
+	/* 10.5.4.5 says not to reset a suspended port if the attached
+	 * device is enabled for remote wakeup.  Hence the reset
+	 * operation is carried out here, after the port has been
+	 * resumed.
+	 */
+	if (udev->reset_resume)
+		status = usb_reset_device(udev);
+
  	/* 10.5.4.5 says be sure devices in the tree are still there.
  	 * For now let's assume the device didn't go crazy on resume,
 	 * and device drivers will know about any resume quirks.
 	 */
+	if (status == 0) {
 		status = usb_get_status(udev, USB_RECIP_DEVICE, 0, &devstatus);
 		if (status >= 0)
 			status = (status == 2 ? 0 : -ENODEV);
+	}
 
 	if (status) {
 		dev_dbg(&udev->dev, "gone after usb resume? status %d\n",
@@ -1735,6 +1689,28 @@ static int finish_port_resume(struct usb_device *udev)
  * the host and the device is the same as it was when the device
  * suspended.
  *
+ * If CONFIG_USB_PERSIST and @udev->reset_resume are both set then this
+ * routine won't check that the port is still enabled.  Furthermore,
+ * if @udev->reset_resume is set then finish_port_resume() above will
+ * reset @udev.  The end result is that a broken power session can be
+ * recovered and @udev will appear to persist across a loss of VBUS power.
+ *
+ * For example, if a host controller doesn't maintain VBUS suspend current
+ * during a system sleep or is reset when the system wakes up, all the USB
+ * power sessions below it will be broken.  This is especially troublesome
+ * for mass-storage devices containing mounted filesystems, since the
+ * device will appear to have disconnected and all the memory mappings
+ * to it will be lost.  Using the USB_PERSIST facility, the device can be
+ * made to appear as if it had not disconnected.
+ *
+ * This facility is inherently dangerous.  Although usb_reset_device()
+ * makes every effort to insure that the same device is present after the
+ * reset as before, it cannot provide a 100% guarantee.  Furthermore it's
+ * quite possible for a device to remain unaltered but its media to be
+ * changed.  If the user replaces a flash memory card while the system is
+ * asleep, he will have only himself to blame when the filesystem on the
+ * new card is corrupted and the system crashes.
+ *
  * Returns 0 on success, else negative errno.
  */
 int usb_port_resume(struct usb_device *udev)
@@ -1743,6 +1719,7 @@ int usb_port_resume(struct usb_device *udev)
 	int		port1 = udev->portnum;
 	int		status;
 	u16		portchange, portstatus;
+	unsigned	mask_flags, want_flags;
 
 	/* Skip the initial Clear-Suspend step for a remote wakeup */
 	status = hub_port_status(hub, port1, &portstatus, &portchange);
@@ -1765,20 +1742,23 @@ int usb_port_resume(struct usb_device *udev)
 				udev->auto_pm ? "auto-" : "");
 		msleep(25);
 
-#define LIVE_FLAGS	( USB_PORT_STAT_POWER \
-			| USB_PORT_STAT_ENABLE \
-			| USB_PORT_STAT_CONNECTION)
-
 		/* Virtual root hubs can trigger on GET_PORT_STATUS to
 		 * stop resume signaling.  Then finish the resume
 		 * sequence.
 		 */
 		status = hub_port_status(hub, port1, &portstatus, &portchange);
-SuspendCleared:
-		if (status < 0
-				|| (portstatus & LIVE_FLAGS) != LIVE_FLAGS
-				|| (portstatus & USB_PORT_STAT_SUSPEND) != 0
-				) {
+
+ SuspendCleared:
+		if (USB_PERSIST && udev->reset_resume)
+			want_flags = USB_PORT_STAT_POWER
+					| USB_PORT_STAT_CONNECTION;
+		else
+			want_flags = USB_PORT_STAT_POWER
+					| USB_PORT_STAT_CONNECTION
+					| USB_PORT_STAT_ENABLE;
+		mask_flags = want_flags | USB_PORT_STAT_SUSPEND;
+
+		if (status < 0 || (portstatus & mask_flags) != want_flags) {
 			dev_dbg(hub->intfdev,
 				"port %d status %04x.%04x after resume, %d\n",
 				port1, portchange, portstatus, status);
@@ -1790,18 +1770,19 @@ int usb_port_resume(struct usb_device *udev)
 						USB_PORT_FEAT_C_SUSPEND);
 			/* TRSMRCY = 10 msec */
 			msleep(10);
-			status = finish_port_resume(udev);
-		}
 		}
-	if (status < 0) {
-		dev_dbg(&udev->dev, "can't resume, status %d\n", status);
-		hub_port_logical_disconnect(hub, port1);
 	}
 
 	clear_bit(port1, hub->busy_bits);
 	if (!hub->hdev->parent && !hub->busy_bits[0])
 		usb_enable_root_hub_irq(hub->hdev->bus);
 
+	if (status == 0)
+		status = finish_port_resume(udev);
+	if (status < 0) {
+		dev_dbg(&udev->dev, "can't resume, status %d\n", status);
+		hub_port_logical_disconnect(hub, port1);
+	}
 	return status;
 }
 
@@ -1830,7 +1811,14 @@ int usb_port_suspend(struct usb_device *udev)
 
 int usb_port_resume(struct usb_device *udev)
 {
-	return 0;
+	int status = 0;
+
+	/* However we may need to do a reset-resume */
+	if (udev->reset_resume) {
+		dev_dbg(&udev->dev, "reset-resume\n");
+		status = usb_reset_device(udev);
+	}
+	return status;
 }
 
 static inline int remote_wakeup(struct usb_device *udev)
@@ -1886,8 +1874,6 @@ static int hub_resume(struct usb_interface *intf)
 
 #ifdef	CONFIG_USB_PERSIST
 
-#define USB_PERSIST	1
-
 /* For "persistent-device" resets we must mark the child devices for reset
  * and turn off a possible connect-change status (so khubd won't disconnect
  * them later).
@@ -1910,8 +1896,6 @@ static void mark_children_for_reset_resume(struct usb_hub *hub)
 
 #else
 
-#define USB_PERSIST	0
-
 static inline void mark_children_for_reset_resume(struct usb_hub *hub)
 { }
 
@@ -1936,6 +1920,24 @@ static int hub_reset_resume(struct usb_interface *intf)
 	return 0;
 }
 
+/**
+ * usb_root_hub_lost_power - called by HCD if the root hub lost Vbus power
+ * @rhdev: struct usb_device for the root hub
+ *
+ * The USB host controller driver calls this function when its root hub
+ * is resumed and Vbus power has been interrupted or the controller
+ * has been reset.  The routine marks @rhdev as having lost power.  When
+ * the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST
+ * is enabled then it will carry out power-session recovery, otherwise
+ * it will disconnect all the child devices.
+ */
+void usb_root_hub_lost_power(struct usb_device *rhdev)
+{
+	dev_warn(&rhdev->dev, "root hub lost power or was reset\n");
+	rhdev->reset_resume = 1;
+}
+EXPORT_SYMBOL_GPL(usb_root_hub_lost_power);
+
 #else	/* CONFIG_PM */
 
 static inline int remote_wakeup(struct usb_device *udev)

drivers/usb/core/usb.h

@@ -36,7 +36,6 @@ extern void usb_host_cleanup(void);
 extern void usb_autosuspend_work(struct work_struct *work);
 extern int usb_port_suspend(struct usb_device *dev);
 extern int usb_port_resume(struct usb_device *dev);
-extern int usb_reset_suspended_device(struct usb_device *udev);
 extern int usb_external_suspend_device(struct usb_device *udev,
 		pm_message_t msg);
 extern int usb_external_resume_device(struct usb_device *udev);