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diff --git a/Documentation/gpu/amdgpu/display/dc-debug.rst b/Documentation/gpu/amdgpu/display/dc-debug.rst new file mode 100644 index 000000000..40c55a618 --- /dev/null +++ b/Documentation/gpu/amdgpu/display/dc-debug.rst @@ -0,0 +1,77 @@ +======================== +Display Core Debug tools +======================== + +DC Visual Confirmation +====================== + +Display core provides a feature named visual confirmation, which is a set of +bars added at the scanout time by the driver to convey some specific +information. In general, you can enable this debug option by using:: + + echo <N> > /sys/kernel/debug/dri/0/amdgpu_dm_visual_confirm + +Where `N` is an integer number for some specific scenarios that the developer +wants to enable, you will see some of these debug cases in the following +subsection. + +Multiple Planes Debug +--------------------- + +If you want to enable or debug multiple planes in a specific user-space +application, you can leverage a debug feature named visual confirm. For +enabling it, you will need:: + + echo 1 > /sys/kernel/debug/dri/0/amdgpu_dm_visual_confirm + +You need to reload your GUI to see the visual confirmation. When the plane +configuration changes or a full update occurs there will be a colored bar at +the bottom of each hardware plane being drawn on the screen. + +* The color indicates the format - For example, red is AR24 and green is NV12 +* The height of the bar indicates the index of the plane +* Pipe split can be observed if there are two bars with a difference in height + covering the same plane + +Consider the video playback case in which a video is played in a specific +plane, and the desktop is drawn in another plane. The video plane should +feature one or two green bars at the bottom of the video depending on pipe +split configuration. + +* There should **not** be any visual corruption +* There should **not** be any underflow or screen flashes +* There should **not** be any black screens +* There should **not** be any cursor corruption +* Multiple plane **may** be briefly disabled during window transitions or + resizing but should come back after the action has finished + +Pipe Split Debug +---------------- + +Sometimes we need to debug if DCN is splitting pipes correctly, and visual +confirmation is also handy for this case. Similar to the MPO case, you can use +the below command to enable visual confirmation:: + + echo 1 > /sys/kernel/debug/dri/0/amdgpu_dm_visual_confirm + +In this case, if you have a pipe split, you will see one small red bar at the +bottom of the display covering the entire display width and another bar +covering the second pipe. In other words, you will see a bit high bar in the +second pipe. + +DTN Debug +========= + +DC (DCN) provides an extensive log that dumps multiple details from our +hardware configuration. Via debugfs, you can capture those status values by +using Display Test Next (DTN) log, which can be captured via debugfs by using:: + + cat /sys/kernel/debug/dri/0/amdgpu_dm_dtn_log + +Since this log is updated accordingly with DCN status, you can also follow the +change in real-time by using something like:: + + sudo watch -d cat /sys/kernel/debug/dri/0/amdgpu_dm_dtn_log + +When reporting a bug related to DC, consider attaching this log before and +after you reproduce the bug. |