On 二, 2012-02-14 at 23:29 +0100, Rafael J. Wysocki wrote:

On Tuesday, February 14, 2012, Zhang Rui wrote:

quoted

Hi, Rafael,

On 一, 2012-02-13 at 21:25 +0100, Rafael J. Wysocki wrote:

quoted

On Monday, February 13, 2012, Lin Ming wrote:

quoted

From: Zhang Rui <rui.zhang@intel.com>

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@intel.com>

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.

Yes, it does.

quoted

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.

That's correct.

quoted

quoted

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.

quoted

quoted

---
 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.

That would be explicitly against the spec that says that power resources
are *required* to have _ON, _OFF and _STA.

quoted

I thought I had seen ACPI Power Resources without _OFF
control method somewhere in bugzilla, but I can not find it out now.

That, clearly, is a firmware bug.

Okay, agreed.
so how about this? _PR3 equals D3_HOT support.

quoted

Hmm, how about set D3_COLD support if _PR3 exists, but leave a warning
message if _OFF doesn't exist, for now?

I don't think we need to set D3_COLD support at all.  In fact, it is always
supported (as I said, if all power resources used by a device are off, the
device is in D3_COLD pretty much by definition).

Yeah, but it seems that Linux uses ACPI_D3 for both ACPICA D3_HOT and D3
(off). I'm generating a patch to remove ACPI_D3_COLD and introduce
D3_HOT support in Linux kernel.

thanks,
rui

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