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Tasklist

FS#77103 - Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.1.5.arch1-1

Attached to Project: Arch Linux
Opened by Roman Petrov (NWhisper) - Thursday, 12 January 2023, 17:03 GMT
Last edited by Toolybird (Toolybird) - Friday, 13 January 2023, 07:20 GMT
Task Type Bug Report
Category Kernel
Status Closed
Assigned To No-one
Architecture x86_64
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Description:

When iMac Mid 2011 boots on kernel versions 6.1.4.arch1-1 and 6.1.5.arch1-1, /sys/class/backlight/radeon_bl0 is missing.
On kernel version 6.1.3.arch1-1 and below everything works normally without changing any settings.

Additional info:

# cat /proc/cmdline
initrd=\intel-ucode.img initrd=\initramfs-linux.img root=UUID=379486b8-e105-46b5-b271-224baff9597c rw quiet acpi_backlight=vendor

# lshw -class display
*-display
description: VGA compatible controller
product: Whistler [Radeon HD 6730M/6770M/7690M XT]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=radeon latency=0
resources: irq:28 memory:90000000-9fffffff memory:a8800000-a881ffff ioport:2000(size=256) memory:a8820000-a883ffff

Steps to reproduce:

1 - On an iMac mid 2011 install Arch Linux with kernel 6.1.[45].arch1-1
2 - Reboot with option acpi_backlight=vendor
3 - Check the directory /sys/class/backlight/radeon_bl0
This task depends upon

Closed by  Toolybird (Toolybird)
Friday, 13 January 2023, 07:20 GMT
Reason for closing:  None
Additional comments about closing:  Reporter says "Solution: acpi_backlight=vendor --> native"
Comment by Rod MacCallum (mrodmac) - Thursday, 12 January 2023, 21:03 GMT
What happens if you boot with the option acpi_backlight=native? This fixed this same issue for me on a 2012 MacBook Pro with intel graphics.
Comment by Roman Petrov (NWhisper) - Friday, 13 January 2023, 06:36 GMT
Indeed, acpi_backlight=native solves the problem completely.

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