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- ========================
- 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.
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