diff options
| author | Mario Limonciello <mario.limonciello@amd.com> | 2025-06-23 12:11:14 -0500 |
|---|---|---|
| committer | Alex Deucher <alexander.deucher@amd.com> | 2025-06-24 10:05:32 -0400 |
| commit | 009bfc5ec5c953534d0f528d1c1e4f60668b7371 (patch) | |
| tree | bb428b3d7e6462ee9448e8dee28622e30a1160f0 /Documentation/gpu/amdgpu | |
| parent | 5b852044eb0d3e1f1c946d32e05fcb068e0a20a0 (diff) | |
drm/amd/display: Add a trace event for brightness programming
[Why]
Brightness programming may involve a conversion of a user requested
brightness against what was in a custom brightness curve. The values
might not match what a user programmed.
[How]
Add a new trace event to show specific converted brightness values.
Reviewed-by: Alex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250623171114.1156451-2-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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 |