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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
To:     rafael@kernel.org, lenb@kernel.org
Cc:     Kai-Heng Feng <kai.heng.feng@canonical.com>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] ACPI: video: Invoke _PS0 at boot for ACPI video
Date:   Tue,  4 Jul 2023 15:45:06 +0800
Message-Id: <20230704074506.2304939-1-kai.heng.feng@canonical.com>
MIME-Version: 1.0
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Screen brightness can only be changed once on some HP laptops.

Vendor identified the root cause as Linux doesn't invoke _PS0 at boot
for all ACPI devices:
    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 ()
                }
            }
	    ...
	}
	...
    }

_PS0 doesn't get invoked for all ACPI devices because of commit
7cd8407d53ef ("ACPI / PM: Do not execute _PS0 for devices without _PSC
during initialization").

For now explicitly call _PS0 for ACPI video to workaround the issue.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/acpi/acpi_video.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 62f4364e4460..793259bd18c8 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -2027,6 +2027,8 @@ static int acpi_video_bus_add(struct acpi_device *device)
 	if (error)
 		goto err_put_video;
 
+	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