[PATCH 0/5] Power supply and resume ordering meddling

Sean McNeil sean at mcneil.com
Tue Jun 10 23:57:28 CEST 2008

Andy Green wrote:
> Somebody in the thread at some point said:
> | I've noticed something else that looks like it could be an hardware
> | issue. LEDs are not able to be lit when you are in suspend mode. This
> | means you can't indicate a charge if you are plugged in and suspended.
> | I can set this capability in my application, but it isn't default
> behavior.
> There shouldn't be a hardware issue with LED state surviving suspend if
> we wanted it in the LED suspend function.  CPU defines the GPIO will
> hold its state during suspend.
Do I have to modify the led class to support this? Is there some 
standard way to export an interface for this? It would be really nice to 
be able to setup the LEDs (at least some of them) so that they stay on 
while in suspend.

> Also power removal or arrival at the USB socket ("USB insert / remove")
> is a wake event if you're suspended; BATFULL can be too although that'll
> get you fake wakes.  So for some kind of events around charging you'll
> get woken up and so have the opportunity to track it a bit, or too much
> or something.
Yes, but if, for example, I setup an LED to indicate a message is 
waiting or the phone is charging and then I initiate a RAM suspend, then 
the light goes out until I wake from an event.
> It's this kind of mungy mess that makes some folks want to have an
> always-on system manangement controller to enforce globally consistent
> behaviours around power independent of the CPU.
> -Andy

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