[Bug 198885] New: amdgpu.dc=1 on CIK (R4 Mullins APU) brightness impossible to change. by Fn or "echo".
bugzilla-daemon at bugzilla.kernel.org
bugzilla-daemon at bugzilla.kernel.org
Thu Feb 22 13:13:21 UTC 2018
https://bugzilla.kernel.org/show_bug.cgi?id=198885
Bug ID: 198885
Summary: amdgpu.dc=1 on CIK (R4 Mullins APU) brightness
impossible to change. by Fn or "echo".
Product: Drivers
Version: 2.5
Kernel Version: 4.15.4
Hardware: x86-64
OS: Linux
Tree: Mainline
Status: NEW
Severity: high
Priority: P1
Component: Video(DRI - non Intel)
Assignee: drivers_video-dri at kernel-bugs.osdl.org
Reporter: soprwa at gmail.com
Regression: No
Created attachment 274359
--> https://bugzilla.kernel.org/attachment.cgi?id=274359&action=edit
dmesg with "amdgpu.dc=1"
I am using gentoo ~amd64, kernel 4.15.4, amdgpu with amdgpu.dc=1 on CIK A6 APU
- R4 Mullins.
There is no possibility to change brightness level both with Fn keys or
directly by an "echo" command, even as root when "amdgpu.dc=1" is set:
ls -l /sys/class/backlight/amdgpu_bl0/
razem 0
-r--r--r-- 1 root root 4096 02-22 13:41 actual_brightness
-rw-r--r-- 1 root root 4096 02-22 13:41 bl_power
-rw-r--r-- 1 root root 4096 02-22 13:41 brightness
lrwxrwxrwx 1 root root 0 02-22 13:41 device -> ../../../0000:00:01.0
-r--r--r-- 1 root root 4096 02-22 13:40 max_brightness
drwxr-xr-x 2 root root 0 02-22 13:41 power
lrwxrwxrwx 1 root root 0 02-22 13:40 subsystem ->
../../../../../class/backlight
-r--r--r-- 1 root root 4096 02-22 13:40 type
-rw-r--r-- 1 root root 4096 02-22 13:39 uevent
"/sys/class/backlight/amdgpu_bl0 # echo 22 > actual_brightness
bash: actual_brightness: permission denied"
and
"/sys/class/backlight/amdgpu_bl0 # echo 128 > brightness
bash: echo: błąd zapisu: Bad argument"
Without "amdgpu.dc=1" in kernel command line changing brightness level is
working as expected, both Fn keys, and echoing directly to a file.
I know that there are plans enabling amdgpu.dc by default, so impossibility to
change brightness level IMHO is a big "no go".
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