On Friday, April 20, 2012, Lin Ming wrote: > On Fri, Apr 20, 2012 at 7:12 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > > 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; > > Will add below change. > > - /* State is valid if we have some power control */ > - if (ps->resources.count || ps->flags.explicit_set) > + /* > + * State is valid if we have some power control > + * D3hot state is only valid if _PR3 present > + */ Well, I'd say: + /* + * State is valid there are means to put the device into it. + * D3hot is only valid if _PR3 present. + */ > + if (ps->resources.count || > + (ps->flags.explicit_set && i < ACPI_STATE_D3_HOT)) > ps->flags.valid = 1; > > Rafael, > > can I still add your ACK when send updated patch? Sure. 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
