linux-kernel - Re: [PATCH] ACPI: evaluate

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Date:	Sun, 1 Apr 2012 13:56:03 +0800
From:	Aaron Lu <aaron.lu@....com>
To:	Lin Ming <ming.m.lin@...el.com>
CC:	Len Brown <lenb@...nel.org>, "Rafeal J. Wysocki" <rjw@...k.pl>,
	<linux-acpi@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Zhang Rui <rui.zhang@...el.com>,
	Andiry Xu <andiry.xu@....com>, Alex He <alex.he@....com>
Subject: Re: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold

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? :-)

Here is the problem, there is no _PR3 in AMD's implementation, just _PS3.
And since _S0W evaluates 4, I've to put this device into D3 cold state
with _PS3.

And the ACPI does have some words like:

------
Platform/drivers must assume that the device will have power completely
removed when the device is place into “D3” via _PS3
------

This is in section 7.2.11: _PR3.

> 
> Another problem:
> 
> With your patch, both D3hot and D3cold will evaluate _PS3, right?
> 
Yes.

> Will it have problem on AMD platform if you try to put ODD into D3hot
> state? _PS3 is evaluated, so it actually enters D3Cold state.

There is no D3 hot support for this device(from the firmware's
perspective), either it is at D0(via _PS0), or it will be at D3 cold(via
_PS3).


Thanks for the review.

-Aaron

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