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SubjectRe: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold
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On 日, 2012-04-01 at 09:23 +0200, Rafael J. Wysocki wrote:
> Hi,
>
> Sorry for the delayed response, I've been travelling recently.
>
> On Sunday, April 01, 2012, Lin Ming wrote:
> > On Sun, 2012-04-01 at 13:56 +0800, Aaron Lu wrote:
> > > Hi,
> > >
> > > On Sun, Apr 01, 2012 at 01:27:33PM +0800, Lin Ming wrote:
> > > > > - if (device->power.states[state].flags.explicit_set) {
> > > > > + /* If state is D3 Cold, try to evaluate _PS3 first */
> > > > > + if (state == ACPI_STATE_D3_COLD) {
> > > > > + explicit_set = (ps - 1)->flags.explicit_set;
> > > > > + object_name[3] -= 1;
> > > > > + }
> > > >
> > > > I'm not sure whether this works or not.
> > > >
> > > > From ACPI spec,
> > > >
> > > > _PS3 "is used to put the specific device into its D3hot or D3 state"
> > > >
> > > > D3 neither means D3hot nor D3cold. It's an old term before D3hot and
> > > > D3cold were introduced.
> > > I guess D3 has to mean something, right? :-)
>
> Well, not necessarily.
>
> The problem is what state the _PS3 method puts the device into: D3_hot or
> D3_cold.
>
> Unfortunately, as far as I can say, ACPI 4.0 didn't specify any "official"
> mapping between the "old" D3 and the "new" D3_{hod|cold} states, so we need to
> figure out something. In my opinion, the only reasonable approach is to
> assume that the state _PS3 puts the device into is always D3_cold, becuase
> _PS3 may remove power completely from the device. It may not do that, but
> we _must_ assume it does that in general.
>
There is a problem that I can think of.
Say currently, ACPI always returns D3 when _PS3 exists.
And this "ACPI_STATE_D3" is translated to PCI_D3hot.
But with this approach, we're going to put these devices to PCI_D3cold
instead, right?
I'm not against this approach, but this may affect a lot of PCI devices,
which we need to take care of, no?

thanks,
rui


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