Hi, Rafael,
On 一, 2012-02-13 at 21:25 +0100, Rafael J. Wysocki wrote:
> On Monday, February 13, 2012, Lin Ming wrote:
> > From: Zhang Rui <rui.zhang@xxxxxxxxx>
> >
> > If a device has _PR3._ON, it means the device supports D3_HOT.
> > If a device has _PR3._OFF, it means the device supports D3_COLD.
> > Add the ability to validate and enter D3_COLD state in ACPI.
> >
> > Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
>
> This is supposed to be ACPI 5.0 support, right?
>
No, D3_HOT is introduced in ACPI spec 4.0.
According to the spec, _PR3 is used for devices that support both
D3(D3_COLD) and D3HOT.
The confusion here is that Linux D3 equals ACPICA D3HOT and Linux
D3_COLD equals ACPICA D3.
For example, when enter Linux ACPI D3, the reference count of ACPI Power
Resources in _PR3 is increased by one.
> So can anyone please tell me what part of the ACPI 5.0 spec is the
> basis of this patch, because I can't see that immediately?
>
> The only places where D3Cold is _mentioned_ are Section 7.2.12 (_PRE, which
> appears to be new in 5.0), Section 7.2.20 (_S0W), Section 7.2.21 (_S1W),
> Section 7.2.22 (_S2W), Section 7.2.23 (_S3W) and Section 7.2.24 (_S4W).
> None of them mentions those _PR3._ON and _PR3._OFF things above.
>
> Moreover, my understanding of the spec is that D3Cold means all of the
> power resources returned by _PR3 are "off" (whereas some of them will be
> "on" in D3hot).
>
Agreed.
> > ---
> > drivers/acpi/power.c | 4 ++--
> > drivers/acpi/scan.c | 10 +++++++++-
> > 2 files changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
> > index 9ac2a9f..0d681fb 100644
> > --- a/drivers/acpi/power.c
> > +++ b/drivers/acpi/power.c
> > @@ -500,14 +500,14 @@ int acpi_power_transition(struct acpi_device *device, int state)
> > {
> > int result;
> >
> > - if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3))
> > + if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3_COLD))
> > return -EINVAL;
> >
> > if (device->power.state == state)
> > return 0;
> >
> > if ((device->power.state < ACPI_STATE_D0)
> > - || (device->power.state > ACPI_STATE_D3))
> > + || (device->power.state > ACPI_STATE_D3_COLD))
> > return -ENODEV;
> >
> > /* TBD: Resources must be ordered. */
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index 8ab80ba..a9d4391 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -881,8 +881,16 @@ static int acpi_bus_get_power_flags(struct acpi_device *device)
> >
> > device->power.flags.power_resources = 1;
> > ps->flags.valid = 1;
> > - for (j = 0; j < ps->resources.count; j++)
> > + for (j = 0; j < ps->resources.count; j++) {
> > acpi_bus_add_power_resource(ps->resources.handles[j]);
> > + /* Check for D3_COLD support. _PR3._OFF equals D3_COLD ? */
> > + if (i == ACPI_STATE_D3) {
> > + if (j == 0)
> > + device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
> > + status = acpi_get_handle(ps->resources.handles[j], "_OFF", &handle);
> > + device->power.states[ACPI_STATE_D3_COLD].flags.valid &= ACPI_SUCCESS(status);
> > + }
> > + }
>
> Sorry, but this doesn't make sense to me. Power resources always have
> the _OFF method, right?
>
I'm not sure. I thought I had seen ACPI Power Resources without _OFF
control method somewhere in bugzilla, but I can not find it out now.
Hmm, how about set D3_COLD support if _PR3 exists, but leave a warning
message if _OFF doesn't exist, for now?
thanks,
rui
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