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    SubjectRe: [PATCH] ACPI: evaluate _PS3 when entering D3 Cold
    Date
    On Sunday, April 01, 2012, Zhang Rui wrote:
    > On 日, 2012-04-01 at 09:47 +0200, Rafael J. Wysocki wrote:
    > > On Sunday, April 01, 2012, Aaron Lu wrote:
    > > > Hi,
    > > >
    > > > On Sun, Apr 01, 2012 at 03:03:39PM +0800, Zhang Rui wrote:
    > > > > First of all, I agree that we must evaluate _PS3 when setting device to
    > > > > either D3_HOT or D3_COLD.
    > > > Good.
    > > >
    > > > >
    > > > > And here is my understanding about D3/D3_HOT/D3_COLD,
    > > > >
    > > > > if _PR3 exists, it means the devices supports both D3_HOT and D3_COLD.
    > > > Agree.
    > > >
    > > > >
    > > > > if only _PS3 exists, we can only say that the state after evaluating
    > > > > _PS3 is D3, it could either be D3_HOT or D3_COLD, and this is device
    > > > > specific, which in your case, is D3_COLD.
    > > > I prefer Rafeal's definition, let's just *assume* the device is at D3
    > > > cold after its _PS3 is executed. Unless it has _PR3, in which case, we
    > > > have a chance to put the device into D3 hot instead.
    > > >
    > > > >
    > > > > BTW, here is the description of _S0W in ACPI spec,
    > > > > If OSPM has not indicated that it supports _PR3 through the OSPM
    > > > > Platform-Wide Capabilities (see Section 6.2.10.2), then the value "3"
    > > > > corresponds to D3. If it has indicated _PR3 support, the value "3"
    > > > > represents D3hot and the value "4" represents D3cold.
    > > > >
    > > > > So IMO, the _S0W should return 3 in AMD's implementation as it does not
    > > > > have _PR3.
    > > > OK, sounds like a firmware bug.
    > > > Thanks for identifying this.
    > >
    > > I don't think this is a bug. It actually may return either 3 or 4, because
    > > there is no difference between them if there's no _PR3 (i.e. the action to
    > > carry out by software would only be different if _PR3 were present).
    > >
    > I mean, surely that software should handle this case.

    Well, exactly. :-)

    > But this is still a violation of ACPI spec, as the device has only one
    > D3 state, instead of D3_HOT/D3_COLD,, thus _S0W should return 3 instead.

    If software is expected to handle that case anyway, I wouldn't really call
    it a violation. What really matters is what software is supposed to do.

    Thanks,
    Rafael
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