On Thu, 28 Mar 2013, Lan Tianyu wrote:
> This patch is to add usb port system pm support. Add
> usb port's system suspend/resume callbacks and call
> usb_port_runtime_resume/suspend() to power off these
> ports whose pm qos NO_POWER_OFF flag is not set, system
> wakeup is disabled and persist is enalbed.
>
> During system pm, usb port should be powered off after
> dev being suspended and powered on before dev being
> resumed. Since usb ports and devs enable async suspend,
> call device_pm_wait_for_dev() in the usb_port_system_suspend()
> and usb_port_resume() to keeping the order.
>
> If usb port was already powered off by runtime pm with
> port_dev->power_is_on being false, usb_port_system_suspend()
> returns directly.
>
> If usb port was not powered off during system suspend with
> port_dev->power_is_on being true, usb_port_system_resume()
> returns directly.
>
> Signed-off-by: Lan Tianyu <tianyu....@intel.com>
...
> +static int usb_port_system_suspend(struct device *dev)
> +{
> + struct usb_port *port_dev = to_usb_port(dev);
> +
> + if (!port_dev->power_is_on)
> + return 0;
> +
> + if (port_dev->child) {
> + struct usb_device *udev = port_dev->child;
> +
> + /*
> + * usb port can't be powered off when dev's system
> + * wakeup is enabled or persist is disabled.
> + */
> + if (device_may_wakeup(&udev->dev)
> + || !udev->persist_enabled)
> + return 0;
> +
> + /*
> + * usb port should be powered off after usb dev
> + * being suspended.
> + */
> + device_pm_wait_for_dev(dev, &port_dev->child->dev);
> + }
> +
> + usb_port_runtime_suspend(dev);
> + return 0;
> +}
What happens if there's no device plugged in to the port, but the hub
is enabled for remote wakeup? How will the hub be able to detect a
plug-in event if the port isn't powered?
Alan Stern
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