The remote firmware does not need to know whether Linux is asleep. The GPIO is not used 
to wake Linux directly; instead, it serves as a wake-up source for the remote firmware if configured 
accordingly. Once the remote firmware is awake, it sends a notification message to Linux. This 
notification is the actual event that wakes Linux.

This works because there is always a physical interface connecting Linux and the remote firmware. 
On i.MX platforms, this interface is the MU block. When the remoteproc driver is running, the MU 
block is automatically configured as a wake-up source for Linux by default. As a result, the notification 
message can wake the Linux system if it is asleep.

You need to add a lot more documentation to the specification to make
this clear. As you said, the firmware and Linux have different
sleep/wake life cycles. How does the firmware know it is safe to go to
sleep, if it has no idea Linux is running or suspended?

	Andrew