On Friday, November 29, 2013 02:52:20 PM Rafael J. Wysocki wrote:

On Friday, November 29, 2013 10:32:06 AM Ulf Hansson wrote:

[...]

quoted

For the same reasons, I believe we should trust drivers/subsystems, to
understand when it makes sense for them to re-use all of the runtime
PM callbacks during system suspend and not just the .runtime_suspend
callback.

That is in principle what I and Alan, who came up with this idea, are
suggesting.

The problem with it is, as I said, the subsystem-level code you're calling
back through pm_generic_suspend_late_runtime() (and the other resume function)
has to be implemented in a specific way for things to work.  So it goes like
this: "OK, now I'm not runtime-suspended, so I need to do something about that.
Why don't I call back to the layer above me that has just called me (and that
surely won't do anything after I return, right?), so that it does the right
thing (which it surely will do, of course?) and calls my runtime PM callback
as expected".

And now suppose that your subsystem-level callbacks look like this (pseudo code):

a_suspend_late(dev)
{
	if (successful(pm_generic_suspend_late(dev)))
		do_X(dev);
}

a_runtime_suspend(dev)
{
	if (successful(pm_generic_runtime_suspend(dev)))
		do_Y(dev);
}

Then, if the driver uses your pm_generic_suspend_late_runtime(), the actually
executed code will be (assuming dev is not runtime-suspended):

	a_suspend_late(dev)
		driver->suspend_late(dev)
			a_runtime_suspend(dev)
				driver->runtime_suspend(dev)
				do_Y(dev)
	do_X(dev)

So what if do_X(dev) after do_Y(dev) doesn't actually work?

And what you actually want is

	driver->runtime_suspend(dev)
	do_Y(dev)

That should have been

 	driver->runtime_suspend(dev)
 	do_X(dev)

because do_Y(dev) is for runtime suspend.  Sorry.

And of course, the subsystem-level code you're developing the driver for may not
do the do_X(dev) thing at all, in which case all will work.  But what if someone
tries to use the driver with a different subsystem-level code (like a new PM
domain)?

Rafael