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Diffstat (limited to 'Documentation/gpu/amdgpu')
| -rw-r--r-- | Documentation/gpu/amdgpu/debugging.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/gpu/amdgpu/debugging.rst b/Documentation/gpu/amdgpu/debugging.rst index 7cbfea0606e1..ac914d524741 100644 --- a/Documentation/gpu/amdgpu/debugging.rst +++ b/Documentation/gpu/amdgpu/debugging.rst @@ -85,3 +85,21 @@ UMR GPU debugging and diagnostics tool. Please see the umr `documentation <https://umr.readthedocs.io/en/main/>`_ for more information about its capabilities. + +Debugging backlight brightness +============================== +Default backlight brightness is intended to be set via the policy advertised +by the firmware. Firmware will often provide different defaults for AC or DC. +Furthermore, some userspace software will save backlight brightness during +the previous boot and attempt to restore it. + +Some firmware also has support for a feature called "Custom Backlight Curves" +where an input value for brightness is mapped along a linearly interpolated +curve of brightness values that better match display characteristics. + +In the event of problems happening with backlight, there is a trace event +that can be enabled at bootup to log every brightness change request. +This can help isolate where the problem is. To enable the trace event add +the following to the kernel command line: + + tp_printk trace_event=amdgpu_dm:amdgpu_dm_brightness:mod:amdgpu trace_buf_size=1M |