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. > > > 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. -Aaron -- 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
