Bug 495003

Summary: KDE doesn't set max. backlight brightness correctly on AMDGPU laptop
Product: [Plasma] plasmashell Reporter: thederpyworld
Component: Power management & brightnessAssignee: Plasma Bugs List <plasma-bugs>
Status: RESOLVED FIXED    
Severity: normal CC: kdedev, kweeky, natalie_clarius, nate
Priority: NOR    
Version First Reported In: 6.2.4   
Target Milestone: 1.0   
Platform: Arch Linux   
OS: Linux   
See Also: https://bugs.kde.org/show_bug.cgi?id=500041
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description thederpyworld 2024-10-18 17:08:24 UTC 
SUMMARY

Changing the backlight brightness using PowerDevil doesn't allow it to go to it absolute potential.

Upon setting the brightness to 100%, we can see that in `/sys/class/backlight/amdgpu_bl1/brightness`  reads 100, however in `max_brighntess` we get 255 and writing that into the brightness file yields a way brighter output.

STEPS TO REPRODUCE
1. Set the brightness to 100% using PowerDevil

OBSERVED RESULT
Display's brightness set to only 100/255.

EXPECTED RESULT
Display's brightness to be set to 255. (`/sys/class/backlight/amdgpu_bl1/max_brightness`)

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.2.1
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0
Kernel Version: 6.9.10-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 16 × AMD Ryzen 7 6800HS with Radeon Graphics
Memory: 14.9 GiB of RAM
Graphics Processor: AMD Radeon 680M

ADDITIONAL INFORMATION

Additional files in the `/sys/class/backlight/amdgpu_bl1`  sysfs (while KDE thinks the backlight is at "100%"):

```
/sys/class/backlight/amdgpu_bl1/actual_brightness : 100
/sys/class/backlight/amdgpu_bl1/bl_power          : 0
/sys/class/backlight/amdgpu_bl1/brightness        : 100
/sys/class/backlight/amdgpu_bl1/type              : raw
/sys/class/backlight/amdgpu_bl1/scale             : unknown
/sys/class/backlight/amdgpu_bl1/max_brightness    : 255
```
Comment 1 Kweeky 2025-03-06 20:22:37 UTC 
I believe I am having the same issue. I have a triple monitor setup (not a laptop), two via DisplayPort, one via HDMI. 

One monitor (the primary monitor - which is connected via DisplayPort), has this exact issue wherein the brightness after wake is limited by powerdevil to 30% on the monitor but powerdevil reports it set to 100%. I can override this with the monitor's hardware controls and increase it to 100% on the monitor, but if I touch powerdevil controls or restart it, it pushes it back down to 30% on the monitor.

This issue didn't seem to happen before last week, but it may be just now apparent since the update to the powerdevil widget which now  reliably persists throughout my session.

Here is the output of `kscreen-doctor-o`:

```
Output: 1 DP-1
        enabled
        connected
        priority 2
        DisplayPort
        Modes:  1:2560x1440@60!  2:2560x1440@75*  3:1920x1200@60  4:1920x1080@120  5:1920x1080@120  6:1920x1080@120  7:1920x1080@100  8:1920x1080@60  9:1920x1080@60  10:1920x1080@60  11:1920x1080@50  12:1600x1200@60  13:1280x1440@60  14:1680x1050@60  15:1280x1024@75  16:1280x1024@60  17:1440x900@60  18:1280x800@60  19:1280x720@60  20:1280x720@60  21:1280x720@50  22:1024x768@120  23:1024x768@100  24:1024x768@75  25:1024x768@70  26:1024x768@60  27:832x624@75  28:800x600@120  29:800x600@100  30:800x600@75  31:800x600@72  32:800x600@60  33:800x600@56  34:720x576@50  35:720x576@50  36:720x480@60  37:720x480@60  38:720x480@60  39:720x480@60  40:640x480@120  41:640x480@100  42:640x480@75  43:640x480@73  44:640x480@67  45:640x480@60  46:640x480@60  47:640x480@60  48:720x400@70  49:1600x1200@60  50:1280x1024@60  51:1024x768@60  52:1920x1200@60  53:1280x800@60  54:2560x1440@60  55:1920x1080@60  56:1600x900@60  57:1368x768@60  58:1280x720@60 
        Geometry: 0,0 2560x1440
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: Never
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: unsupported
Output: 2 DP-2
        enabled
        connected
        priority 1
        DisplayPort
        Modes:  59:2560x1440@60!  60:2560x1440@144*  61:2560x1440@120  62:2560x1440@100  63:1920x1200@60  64:1920x1080@120  65:1920x1080@120  66:1920x1080@60  67:1920x1080@60  68:1920x1080@60  69:1920x1080@50  70:1600x1200@60  71:1280x1440@60  72:1680x1050@60  73:1280x1024@75  74:1280x1024@60  75:1440x900@60  76:1280x800@60  77:1280x720@60  78:1280x720@60  79:1280x720@50  80:1024x768@120  81:1024x768@100  82:1024x768@75  83:1024x768@70  84:1024x768@60  85:832x624@75  86:800x600@120  87:800x600@100  88:800x600@75  89:800x600@72  90:800x600@60  91:800x600@56  92:720x576@50  93:720x576@50  94:720x480@60  95:720x480@60  96:720x480@60  97:720x480@60  98:640x480@120  99:640x480@100  100:640x480@75  101:640x480@73  102:640x480@67  103:640x480@60  104:640x480@60  105:640x480@60  106:720x400@70  107:1600x1200@60  108:1280x1024@60  109:1024x768@60  110:1920x1200@60  111:1280x800@60  112:2560x1440@60  113:1920x1080@60  114:1600x900@60  115:1368x768@60  116:1280x720@60 
        Geometry: 2560,0 2560x1440
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: Never
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: supported, set to 100% and dimming to 100%
Output: 3 HDMI-A-1
        enabled
        connected
        priority 3
        HDMI
        Modes:  117:2560x1440@60!  118:2560x1440@75*  119:1920x1200@60  120:1920x1080@120  121:1920x1080@120  122:1920x1080@120  123:1920x1080@100  124:1920x1080@60  125:1920x1080@60  126:1920x1080@60  127:1920x1080@50  128:1600x1200@60  129:1280x1440@60  130:1680x1050@60  131:1280x1024@75  132:1280x1024@60  133:1440x900@60  134:1280x800@60  135:1280x720@60  136:1280x720@60  137:1280x720@50  138:1024x768@120  139:1024x768@100  140:1024x768@75  141:1024x768@70  142:1024x768@60  143:832x624@75  144:800x600@120  145:800x600@100  146:800x600@75  147:800x600@72  148:800x600@60  149:800x600@56  150:720x576@50  151:720x576@50  152:720x480@60  153:720x480@60  154:720x480@60  155:720x480@60  156:640x480@120  157:640x480@100  158:640x480@75  159:640x480@73  160:640x480@67  161:640x480@60  162:640x480@60  163:640x480@60  164:720x400@70  165:1600x1200@60  166:1280x1024@60  167:1024x768@60  168:1920x1200@60  169:1280x800@60  170:2560x1440@60  171:1920x1080@60  172:1600x900@60  173:1368x768@60  174:1280x720@60 
        Geometry: 5120,0 2560x1440
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: Never
        RgbRange: unknown
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: unsupported
```
Comment 2 Nate Graham 2025-05-20 18:17:53 UTC 
Thanks for the bug report, and I'm sorry we weren't able to get to this yet? Can I ask if you're still able to reproduce the issue with Plasma 6.3.5 and ddcutil 2.2.0 or later?
Comment 3 thederpyworld 2025-05-28 14:54:09 UTC 
(In reply to Nate Graham from comment #2)
> Thanks for the bug report, and I'm sorry we weren't able to get to this yet?
> Can I ask if you're still able to reproduce the issue with Plasma 6.3.5 and
> ddcutil 2.2.0 or later?

Sorry for taking so long to respond -- I don't seem to be able to reproduce it now, however since the time I've reported it originally I have finally switched to Wayland, so I'm not sure if it still occurs (or if it even has a different code path) on X11.

For the sake of verbosity, the current configuration:

Operating System: Arch Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.14.7-zen2-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 6800HS with Radeon Graphics
Memory: 14.9 GiB of RAM
Graphics Processor 1: AMD Radeon 680M
Graphics Processor 2: llvmpipe
Manufacturer: ASUSTeK COMPUTER INC.
Product Name: ROG Zephyrus G15 GA503RM_GA503RM
System Version: 1.0

```
$ pacman -Q ddcutil
ddcutil 2.2.0-1
```

And the `amdgpu_bl1/*` sysfs files:

```
/sys/class/backlight/amdgpu_bl1/actual_brightness:255
/sys/class/backlight/amdgpu_bl1/bl_power:0
/sys/class/backlight/amdgpu_bl1/brightness:255
/sys/class/backlight/amdgpu_bl1/max_brightness:255
/sys/class/backlight/amdgpu_bl1/scale:unknown
/sys/class/backlight/amdgpu_bl1/type:raw
```
Comment 4 Nate Graham 2025-05-28 18:49:15 UTC 
Great, let's assume it was either fixed, or it's only seen on X11. Calling it fixed!