Re: [PATCH] implement pm_ops.valid for everybody

Guennadi Liakhovetski
2007-03-21T22:36:55Z

On Wed, 21 Mar 2007, David Brownell wrote:

> On Wednesday 21 March 2007 2:01 pm, Guennadi Liakhovetski wrote:
>
> > May we agree on some "simple" criteria, like "CPU power on, i.e.,
> > CPU registers preserved"? If yes - standby, CPU off, registers lost - StR?
>
> The ACPI spec has some verbiage on those things, which uses
> roughly that distinction.
>
> Which is very much an indication of how weak ACPI is. It
> doesn't contemplate typical SOC behavior, which have a wide
> variety of system sleep states that leave the CPU on ... and
> which may not even *have* (or need!) a "cpu off" state.
>
> My own definition would be more like: the minimal RAM-based
> power-saving system state is "standby". If the system
> implements a deeper RAM-based system sleep state, that's "STR".

Hmmm, this leaves the decision how to call each state COMPLETELY to the
implementor, doesn't it? For example, in my suspend above, I do put the
peripheral controller to sleep too, whereas a "minimal RAM-based" suspend
could leave it on. So, does it mean I already qualify for StR?:-) I am
sure you have more experience with power management and a better
understanding of it too, maybe that's the reason why your definition makes
a good sense to you and not to me. But "suspend to RAM" - I think it would
be logical to interpret it as "only system RAM contents is preserved. All
other volatile storage (CPU registers, peripheral internal registers and
RAM, etc.) contents is lost."

Thanks
Guennadi
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Guennadi Liakhovetski