Re: Nested suspends; messages vs. states

Patrick Mochel
2005-03-24T17:41:07Z

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On Thu, 24 Mar 2005, David Brownell wrote:

> On Thursday 24 March 2005 9:00 am, Patrick Mochel wrote:
>
> > > Other platforms could use the same names differently of course. Capsule
> > > summary, "deep" means there's only a 32KHz clock, while "big" means the
> > > 48 MHz one is available to peripherals that need it (UARTs, USB, MMC/SD,
> > > camera, and so forth).
> >
> > It sounds like they refer to low-power states in which the system is still
> > operating, which are distinct from the STD/STR/Standby that we're used to
> > that are non-operational low-power states. Is that correct?
>
> Well, _some_ parts of the system are still operating. But that's
> true of STR/Standby too ... some components are operating well
> enough to issue wakeup events. (Even in some STD modes.) And
> return from STR/Standby does't mean all device state is trashed;
> those devices don't go "non-operational" as in "reset" either.

That's a bit of a stretch. While it's true that some devices can generate
wakeup interrupts, they are not servicing normal requests. Enabling the
wakeup events seems to imply disabling other services.

It sounds like in the case you speak of, the devices are still doing
'normal' work, but it also seems like that normal work is self-contained
in the device and doesn't need any code executed on a CPU to do so (like
via an ISR).

Pat