Vitaly Wool [off-list ref] writes:

Hi Kevin,

quoted

Therefore, what is ideally needed is the ability for A's suspend to
simply call pm_runtime_suspend() so the subsystem can do the work.
However, since runtime transitions are locked out by this time, that
doesn't work.  IOW, what is needed is a way for a system suspend to say
"please finish the runtime suspend that was already requested."

What I've done to work around this in driver A is to manually check
pm_runtime_suspended() and directly call the subsystem's runtime
suspend/resume (patch below[1].  NOTE, I've used the _noirq methods to
ensure device A is available when device B needs it.)

suppose this driver runs on a platform that has runtime PM disabled.
How is it going to work then?

Then pm_runtime_suspended() will be false, and the bus methods will
suspend the device.

Kevin