Bug 203427 - [REG 4.20 -> 5.0] AMD brightness minimum level is too high
Summary: [REG 4.20 -> 5.0] AMD brightness minimum level is too high
Status: RESOLVED DUPLICATE of bug 203439
Alias: None
Product: ACPI
Classification: Unclassified
Component: Power-Video (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: acpi_power-video
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2019-04-25 22:10 UTC by Błażej Szczygieł
Modified: 2019-04-26 16:41 UTC (History)
0 users

See Also:
Kernel Version: 5.0
Subsystem:
Regression: No
Bisected commit-id:

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Description Błażej Szczygieł 2019-04-25 22:10:59 UTC 
I have Huawei Matebook D 14 with AMD Ryzen 2500U.

Since kernel 5.0.x the minimum brightness level is too high. It is not possible to dim the display as much as on previous kernel version. Kernel 4.20 also allows to disable the backlight on level 0.

Value of "0" in "/sys/class/backlight/amdgpu_bl0/brightness" currently doesn't disable backlight as in previous version. Value of "1" means the screen is dim, but not as much as in kernel 4.20. Sometimes the screen is still too bright even on level 0 in kernel 5.0.

Since commit 206bbafe00dcacccf40e6f09e624329ec124201b I can see the define:
> #define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12

Maybe it should be defined to "0" to restore the old behavior? (I haven't tested yet)
Comment 1 Błażej Szczygieł 2019-04-26 16:41:31 UTC 
Moved here: https://bugzilla.kernel.org/show_bug.cgi?id=203439

It should be better section to report the amdgpu issue.

*** This bug has been marked as a duplicate of bug 203439 ***
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