* Rafael J. Wysocki [off-list ref] [171108 00:25]:

On Tuesday, November 7, 2017 5:00:06 PM CET Tony Lindgren wrote:

quoted

For runtime PM, restoring the state constantly is unnecessary and not
good for battery life. The logic can be just:

1. Device driver runtime PM suspend saves the state when needed

2. Device driver runtime PM resume checks if context_lost was set by
   the bus or power domain code

3. If context was lost, device driver restores the state, or in some
   cases may need re-run the driver register init related parts
   to bring the driver back up, then clears the context_lost flag

How about something like the following patch? So far only compile
tested with CONFIG_PM enabled. If that looks like the way to go,
I'll test it properly and add some comments for the functions and
post a proper patch :)

Honestly, I'm not sure.

I'd rather have a context_lost flag to start with and see how/if
drivers will use that before adding any common infra for handling
this.

Right, I'll provide some use cases but it will be a little while.

Currently it's done in non-generic way at the interconnect code
for my use cases:

$ git grep "\.context_offs = " arch/arm/mach-omap2/*data.c | wc -l
276

It seems that we could have genpd take care of this in a generic
way with the patch I posted.

Regards,

Tony