When I am checking usb remote wakeup code, I found that usb remote wakeup will
not work after system going to S3 sate and I confirmed with my PC.
During enumeration, usb device will be set as wakeup capable by
usb_set_device_state if it supports. Whether usb driver send
SET_FEATURE(REMOTE_WAKUP) usb request when suspending on S3 depend on
do_remote_wakeup flag which is set by choose_wakeup(). It can be simply
presented as below.
do_remote_wakeup = device_may_wakeup(&udev->dev);
The return value is always false since usb device is not marked as wakeup
enabled(that is no one call device_set_wakeup_enable() for usb device). As a
result, usb device will not signal wakeup event to host.
Maybe we should not allow all remote wakeup supported device can wakeup system
by default. But for usb keyboard/mouse, I think it is not reasonable to disable
it by default.
A simple way to fix this is that replace the device_may_wakeup by
device_can_wakeup in choose_wakeup() function, just like on auto suspend case
(usb remote wakeup works for rpm). Another way is to make usb device wakeup
able by default. But both of them will make all usb devices can wakeup system.
Have any better idea?
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