[Bug 106228] amdgpu reads back brightness 0 (which is not true) if checked before a brightness has been explicitly set
https://bugs.freedesktop.org/show_bug.cgi?id=106228
Bug ID: 106228 Summary: amdgpu reads back brightness 0 (which is not true) if checked before a brightness has been explicitly set Product: DRI Version: unspecified Hardware: Other OS: Linux (All) Status: NEW Severity: normal Priority: medium Component: DRM/AMDgpu Assignee: dri-devel@lists.freedesktop.org Reporter: jian-hong@endlessm.com
Created attachment 139091 --> https://bugs.freedesktop.org/attachment.cgi?id=139091&action=edit The full dmesg
I have tried to install Linux OS on ASUS laptop which is equipped with AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx.
When the Linux installation completed and entered to the OS, the brightness of display looks normal but the brightness bar is shown as the lowest level within the display's brightness GUI setting.
Also check "cat /sys/class/backlight/amdgpu_bl0/brightness" and it is 0.
After a system reboot, Brightness is dimmed to the lowest level. Check "cat /sys/class/backlight/amdgpu_bl0/brightness" again and it is 12.
To make sure it is the problem that "system always reads back brightness 0 if checked before a brightness has been explicitly set". I disable all of the brightness setting applications, including masking systemd-backlight service and than reboot. "cat /sys/class/backlight/amdgpu_bl0/brightness" before set brightness manually again and it reads back 0, but the brightness of display looks normal actually. Then, if I drag the brightness bar in GUI, the actual brightness changes and the "/sys/class/backlight/amdgpu_bl0/brightness" goes to the right value. And, I reboot again, then the same things happen again.
I also tried this with kernel v4.17.0-rc2. It still has the same problem.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #1 from Alex Deucher alexdeucher@gmail.com --- Harry, I thought we fixed something like this recently. Maybe this patch? https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #2 from Harry Wentland harry.wentland@amd.com --- That patch only affects Carrizo and should only be needed for S3.
We don't see this issue with Ubuntu 18.04 on a Raven laptop we have available. The OS (Gnome) shows brightness as expected on boot.
I wonder if some laptops behave differently but I can't think why.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #3 from Daniel Drake dan@reactivated.net --- Do you have any specific debugging suggestions? Can we ship an affected laptop to you for diagnosis?
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #4 from David Francis david.francis@amd.com --- Created attachment 140795 --> https://bugs.freedesktop.org/attachment.cgi?id=140795&action=edit Patch that should fix the problem
Could you try out this patch and check if it works? Thanks.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #5 from Daniel Drake dan@reactivated.net --- Created attachment 140809 --> https://bugs.freedesktop.org/attachment.cgi?id=140809&action=edit additional patch
this patch may also be required
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #6 from jian-hong@endlessm.com --- Apply "[PATCH] drm/amdgpu: Read back max backlight value at boot" to Linux 4.18.0-rc6 kernel.
I disable all of the brightness setting applications, including masking systemd-backlight service and than reboot. "cat /sys/class/backlight/amdgpu_bl0/brightness" before set brightness manually again and it reads back 255 (the maximum brightness).
If I unmask systemd-backlight service and than reboot for test, "cat /sys/class/backlight/amdgpu_bl0/brightness" before set brightness manually again and it reads back the brightness which is saved before last reboot.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #7 from jian-hong@endlessm.com --- Applied both "[PATCH] drm/amdgpu: Read back max backlight value at boot" and "[PATCH] drm/amd/display: Implement backlight_ops.get_brightness" to Linux 4.18.0-rc6 kernel.
I got the same behavior as previous comment.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
--- Comment #8 from David Francis david.francis@amd.com --- When systemd-backlight is disabled, on reboot is the actual brightness coming from the monitor maximum?
If it is, I believe this is working as intended.
https://bugs.freedesktop.org/show_bug.cgi?id=106228
jian-hong@endlessm.com changed:
What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|NEW |RESOLVED
--- Comment #9 from jian-hong@endlessm.com --- Hi David,
Yes! It is. Thanks
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