Created attachment 274359 [details] 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".
(In reply to Przemek from comment #0) > -r--r--r-- 1 root root 4096 02-22 13:41 actual_brightness [...] > "/sys/class/backlight/amdgpu_bl0 # echo 22 > actual_brightness > bash: actual_brightness: permission denied" As you can see above, this file is read-only. > "/sys/class/backlight/amdgpu_bl0 # echo 128 > brightness > bash: echo: błąd zapisu: Bad argument" What does cat max_brightness say? If it's a value smaller than 128, does writing a value <= that to the brightness file work? > Without "amdgpu.dc=1" in kernel command line changing brightness level is > working as expected, both Fn keys, and echoing directly to a file. What values do the brightness, max_brightness and actual_brightness files contain in that case?
Hi Michel, Thank you very much for insane-fast response. Yes, "actual_brightness" is a bad example, same occurs on this file without "amdgpu.dc=1". Here are values from requested files: "/sys/class/backlight/amdgpu_bl0 # cat brightness 3" "/sys/class/backlight/amdgpu_bl0 # cat max_brightness 255" "/sys/class/backlight/amdgpu_bl0 # cat actual_brightness 3" I have tried different values also: "/sys/class/backlight/amdgpu_bl0 # echo 100 > brightness bash: echo: błąd zapisu: Bad argument /sys/class/backlight/amdgpu_bl0 # echo 50 > brightness bash: echo: błąd zapisu: Bad argument /sys/class/backlight/amdgpu_bl0 # echo 10 > brightness bash: echo: błąd zapisu: Bad argument"
And here values from requested files without "amdgpu.dc=1" "/sys/class/backlight/amdgpu_bl0 # ls -l razem 0 -r--r--r-- 1 root root 4096 02-22 17:50 actual_brightness -rw-r--r-- 1 root root 4096 02-22 17:50 bl_power -rw-r--r-- 1 root root 4096 02-22 17:39 brightness lrwxrwxrwx 1 root root 0 02-22 17:50 device -> ../../card0-eDP-1 -r--r--r-- 1 root root 4096 02-22 17:39 max_brightness drwxr-xr-x 2 root root 0 02-22 17:50 power lrwxrwxrwx 1 root root 0 02-22 17:39 subsystem -> ../../../../../../../class/backlight -r--r--r-- 1 root root 4096 02-22 17:39 type -rw-r--r-- 1 root root 4096 02-22 17:38 uevent" "/sys/class/backlight/amdgpu_bl0 # cat brightness 23" "/sys/class/backlight/amdgpu_bl0 # cat actual_brightness 23" "/sys/class/backlight/amdgpu_bl0 # cat max_brightness 255" With smaller values from previous post (with "amdgpu.dc=1" on kernel commandline) screen is much brighter, as backlight was set almost 100%.
Thanks for reporting this. It's currently not hooked up for ASICs older than Carrizo. We'll take a look. You're right that it clashes with the kernel's 'no regressions' policy should we change pre-VEGA ASIC support with DC to enabled by default.
(In reply to Harry Wentland from comment #4) > Thanks for reporting this. It's currently not hooked up for ASICs older than > Carrizo. We'll take a look. > > You're right that it clashes with the kernel's 'no regressions' policy > should we change pre-VEGA ASIC support with DC to enabled by default. Hi Harry, I am glad to hear that the reason is already known, and we are not searching it blindly. There is still time till 4.17 merge window ends, so if you would like me to try out some patches, please do not hesitate. Thanks, Przemek.
Can you try the drm-next-4.17-wip branch from https://cgit.freedesktop.org/~agd5f/linux? This should be fixed there.
Sorry for the delay but I had to git clone whole agd5f branch repo once again since I was moving my installation to another drive. Moreover I had kernel panic with PSP platform module turned on (CONFIG_CRYPTO_DEV_SP_PSP), but it is not the case of this bug report. (BTW as from the specs this apu has one included). Brightness keys are working as expected, /sys/class/backlight/amdgpu_bl0/brightness is now editable by "echo", Display Core is initialized with v3.1.40, so I am closing this bug report as solved/code fix. Thank you very much for fast and accurate action on this. Done to a turn. Thanks once again, Przemek.