[L/M] [PATCH 1/1] ACPI: video: Put ACPI video and its child devices into D0 on boot

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/2032704

Screen brightness can only be changed once on HP ZBook Fury 16 G10.

The vendor reports that the issue is related to the fact that Linux doesn't
invoke _PS0 at boot for all ACPI devices, as expected by the platform firmware:

    Scope (\_SB.PC00.GFX0)
    {
        Scope (DD1F)
        {
            Method (_PS0, 0, Serialized)  // _PS0: Power State 0
            {
                If (CondRefOf (\_SB.PC00.LPCB.EC0.SSBC))
                {
                    \_SB.PC00.LPCB.EC0.SSBC ()
                }
            }
	    ...
	}
	...
    }

The \_SB.PC00.GFX0.DD1F is the panel device, and its _PS0 needs to be
executed at the initialization time to make the brightness control work
properly.

_PS0 is not evaluated for this device, because _PSC is missing,
which violates the ACPI specification (ACPI 6.5, section 7.3.6).

Commit b3785492268f ("ACPI / PM: Do not power manage devices in unknown
initial states") tried to work around missing _PSC on platforms with
defective firmware, but got reverted due to a regression.

So the safest approach is to use acpi_device_fix_up_power_extended() to
put ACPI video and its child devices to D0 to address the issue at hand.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217683
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
Reviewed-by: Hans de Goede <hdegoede at redhat.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
(cherry picked from commit 89c290ea758911e660878e26270e084d862c03b0 linux-next)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/acpi/acpi_video.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 62f4364e4460..1732780a672b 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2027,6 +2027,12 @@ static int acpi_video_bus_add(struct acpi_device *device)
 	if (error)
 		goto err_put_video;
 
+	/*
+	 * HP ZBook Fury 16 G10 requires ACPI video's child devices have _PS0
+	 * evaluated to have functional panel brightness control.
+	 */
+	acpi_device_fix_up_power_extended(device);
+
 	pr_info("%s [%s] (multi-head: %s  rom: %s  post: %s)\n",
 	       ACPI_VIDEO_DEVICE_NAME, acpi_device_bid(device),
 	       video->flags.multihead ? "yes" : "no",
-- 
2.34.1