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| H A D | acpi_video.c | diff 89c290ea758911e660878e26270e084d862c03b0 Fri Jul 21 17:21:43 CEST 2023 Kai-Heng Feng <kai.heng.feng@canonical.com> ACPI: video: Put ACPI video and its child devices into D0 on boot
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@canonical.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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