Have dev_pm_ops.prepare return 1 for USB devices and ports so that USB
devices can remain runtime-suspended when the system goes to a sleep
state, if their wakeup state is correct and they have runtime PM enabled.

Signed-off-by: Tomeu Vizoso <tomeu.viz...@collabora.com>
Reviewed-by: Ulf Hansson <ulf.hans...@linaro.org>
Acked-by: Alan Stern <st...@rowland.harvard.edu>
---

Changes in v10:
- Remove superfluous call to pm_runtime_enabled() as suggested by Alan

 drivers/usb/core/port.c | 6 ++++++
 drivers/usb/core/usb.c  | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 210618319f10..f49707d73b5a 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -168,12 +168,18 @@ static int usb_port_runtime_suspend(struct device *dev)
 
        return retval;
 }
+
+static int usb_port_prepare(struct device *dev)
+{
+       return 1;
+}
 #endif
 
 static const struct dev_pm_ops usb_port_pm_ops = {
 #ifdef CONFIG_PM
        .runtime_suspend =      usb_port_runtime_suspend,
        .runtime_resume =       usb_port_runtime_resume,
+       .prepare =              usb_port_prepare,
 #endif
 };
 
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 8d5b2f4113cd..3a55c91b13a1 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -316,7 +316,13 @@ static int usb_dev_uevent(struct device *dev, struct 
kobj_uevent_env *env)
 
 static int usb_dev_prepare(struct device *dev)
 {
-       return 0;               /* Implement eventually? */
+       struct usb_device *udev = to_usb_device(dev);
+
+       /* Return 0 if the current wakeup setting is wrong, otherwise 1 */
+       if (udev->do_remote_wakeup != device_may_wakeup(dev))
+               return 0;
+
+       return 1;
 }
 
 static void usb_dev_complete(struct device *dev)
-- 
2.5.0

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