ÔÚ 2012-4-20£¬ÏÂÎç7:08£¬"Rafael J. Wysocki" дµÀ£º > On Friday, April 20, 2012, Aaron Lu wrote: >> Hi, >> >> On Fri, Apr 20, 2012 at 01:37:35PM +0800, Lin Ming wrote: >>>>>>> There are two ACPI D3 states defined now: >>>>>>> ACPI_STATE_D3 and ACPI_STATE_D3_COLD. >>>>>>> >>>>>>> But the uses of these states are not clear/correct in some code. >>>>>>> For example, some code refer ACPI_STATE_D3 as D3hot and others refer >>>>>>> it as D3cold. >>>>>>> >>>>>>> This patch introduces ACPI_STATE_D3_HOT to refer to ACPI D3hot state. >>>>>>> And changes ACPI_STATE_D3 to refer to ACPI D3cold state only. >>>>>>> Also redefines ACPI_STATE_D3_COLD the same as ACPI_STATE_D3. >>>>>>> >>>>>> >>>>>> With this patch now, if a device has _PS3, then we will set its D3hot >>>>>> flag valid. This doesn't feel right to me, since per our discussion the >>>>>> other day, we should assume _PS3 will put the device into D3cold. >>>>>> >>>>>> Or do you mean: if _PS3 is available, then both D3hot and D3cold is >>>>>> valid from the perspective of acpi, it is the individual driver's >>>>>> responsibility to decide which state is actually valid and will be used. >>>>> >>>>> Right. >>>>> >>>>> ACPI_STATE_D3(same as ACPI_STATE_D3_COLD now) is always valid. >>>>> >>>> >>>> I mean, if _PS3 is available, can we say D3hot is valid? >>> >>> Yes. >>> >> >> OK, now I'm confused... >> >> First, let me try to clarify the meaning of acpi power state's valid >> flag. >> >> By valid, I suppose it means the device can be in that state, instead of >> we have a way to program this device to go into that state. >> >> e.g. D0 is valid means the device can be in D0 state, and D3_cold is >> valid means the device can be in D3_cold state. We unconditionally set >> these two states as valid, because we know every device supports these >> two states. But we might not be able to put the device into that state >> in software, since we might not have _PS0 or _PS3 control methods for it. >> >> And if we do have the _PSx or _PRx control methods, we knows we have a >> way to put the device into that state, and hence the device should be >> able to support that power state, so we will set that state as valid too. >> >> Is this correct? >> >> For D3hot, obviously not all device supports this state, so we will need >> to figure it out through the acpi table. >> I remembered Rafael said the following words the other day in a reply to >> my evaluate_ps3_when_entering_d3_cold_patch: >> >> ----------------------------------------------------------------------- >> I'd rather say that with _PR3 we have the opportunity to avoid removing >> power completely from the device. In other words, D3_hot is supported (and >> it is supported _only_ in that case). >> ----------------------------------------------------------------------- >> >> So I think here is a problem, that if a device has only _PS3, why should >> we say D3hot is supported? Is there a reason for this that I missed? > > OK, I agree. We need to special case the situation in which _PR3 is not > present, but _PS3 is. IOW, we should do something like this in the loop in > acpi_bus_get_power_flags(): > > > /* State is valid if we have some power control */ > if (ps->resources.count > || (ps->flags.explicit_set && i < ACPI_STATE_D3)) > ps->flags.valid = 1; > Looks good to me, thanks. -Aaron