USB: skip autosuspended devices during system resume

System suspends and hibernation are supposed to be as transparent as
possible.  By this reasoning, if a USB device is already autosuspended
before the system sleep begins then it should remain autosuspended
after the system wakes up.

This patch (as1001) adds a skip_sys_resume flag to the usb_device
structure and uses it to avoid waking up devices which were suspended
when a system sleep began.

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

2 files changed, 21 insertions, 7 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 3f734240e0ec..8c1eac27f2de 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1540,9 +1540,21 @@ int usb_external_resume_device(struct usb_device *udev)
 
 static int usb_suspend(struct device *dev, pm_message_t message)
 {
+        struct usb_device       *udev;
+
         if (!is_usb_device(dev))        /* Ignore PM for interfaces */
                 return 0;
-        return usb_external_suspend_device(to_usb_device(dev), message);
+        udev = to_usb_device(dev);
+
+        /* If udev is already suspended, we can skip this suspend and
+         * we should also skip the upcoming system resume. */
+        if (udev->state == USB_STATE_SUSPENDED) {
+                udev->skip_sys_resume = 1;
+                return 0;
+        }
+
+        udev->skip_sys_resume = 0;
+        return usb_external_suspend_device(udev, message);
 }
 
 static int usb_resume(struct device *dev)
@@ -1553,13 +1565,14 @@ static int usb_resume(struct device *dev)
                 return 0;
         udev = to_usb_device(dev);
 
-        /* If autoresume is disabled then we also want to prevent resume
-         * during system wakeup.  However, a "persistent-device" reset-resume
-         * after power loss counts as a wakeup event.  So allow a
-         * reset-resume to occur if remote wakeup is enabled. */
-        if (udev->autoresume_disabled) {
+        /* If udev->skip_sys_resume is set then udev was already suspended
+         * when the system suspend started, so we don't want to resume
+         * udev during this system wakeup.  However a reset-resume counts
+         * as a wakeup event, so allow a reset-resume to occur if remote
+         * wakeup is enabled. */
+        if (udev->skip_sys_resume) {
                 if (!(udev->reset_resume && udev->do_remote_wakeup))
-                        return -EPERM;
+                        return -EHOSTUNREACH;
         }
         return usb_external_resume_device(udev);
 }
diff --git a/include/linux/usb.h b/include/linux/usb.h
index c10935fdc03a..c5c8f169d3cf 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -430,6 +430,7 @@ struct usb_device {
         unsigned persist_enabled:1;     /* USB_PERSIST enabled for this dev */
         unsigned autosuspend_disabled:1; /* autosuspend and autoresume */
         unsigned autoresume_disabled:1;  /*  disabled by the user */
+        unsigned skip_sys_resume:1;     /* skip the next system resume */
 #endif
 };
 #define to_usb_device(d) container_of(d, struct usb_device, dev)