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. 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. thanks, rui > > > > 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 > > > > ------ > > > > > > > I think this means OS can not access device any more after evaluating > > > _PS3, and it should re-enumerate the device when transiting back to D0. > > > > > > > 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). > > > > > > > I was trying to make a cleanup of the D3/D3_HOT/D3_COLD support in > > > Linux, and this gives me some clue. > > This is great, and I would like to help as much as I can. > > > > > > > > How about this? > > > > > > We should use the term "D3" in general in Linux. > > > Without _PR3, OS should *assume* that the power is removed, although it > > > may be not true. > > > With _PR3, OS can *assure* that the power is removed, because it knows > > > how to remove thw power (evaluating _PR3._OFF). > > > > > > So the difference is that OS need to make sure whether to evaluate > > > _PR3._OFF when _PR3 exists. For example, a device has _PR3, but _S0W > > > returns 3, OS should not evaluate _PR3._OFF when the device sleeps with > > > remote wakeup support. > > > > > > what do you think? > > I agree with Rafeal's ideas. > > Good. :-) > > Thanks, > Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
