Re: Nested suspends; messages vs. states

David Brownell
2005-03-24T16:38:37Z

[-- Attachment #1: Type: text/plain, Size: 1683 bytes --]

On Thursday 24 March 2005 7:48 am, Patrick Mochel wrote:
>
> On Thu, 24 Mar 2005, Pavel Machek wrote:
>
> > Seems to me that suspend-to-RAM and suspend-to-DISK make sense, and
> > cover 90% of what people want to do. Add "standby" for "fast
> > suspend-to-RAM" and you cover even ARM. I'd say that's good enuogh.
>
> We can treat STR and Standby nearly identically, exceptions being what we
> do with the CPU, and what power states the devices enter. But, are there
> any others?

Quite possibly. Also look at the Montavista DPM stuff, where the
operating points are a superset of those CPU states ...

> What about this "big sleep" and "deep sleep" stuff? What platform were
> those for? Is there documentation about them?

The terms apply at least to OMAP, and there's plenty of documentation
for those chips. Look at the OMAP 5912 docs:

http://focus.ti.com/omap/docs/omapgenpage.tsp?navigationId=12341&templateId=5663&path=templatedata/cm/omapproc/data/omap5912

You'll have to register to get those (vs an NDA for an almost-identical
version used inside cell phones -- yes, some Linux based ones too! -- which
is one-big-PDF instead of lots of little one-per-chapter ones) and then
the "Power Management" reference guide, SPRU753, talks about those details.

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).

Other ARM SOCs have similar distinctions; you might look at the Atmel
AT91rm9200 for one that's a lot simpler (and where Linux support isn't
quite as mature).

- Dave