Display Controller Debug

U-Boot stores its debug settings in the following file: freelight-u-sdk/u-boot/driver/core/Kconfig.

Prerequisites

Before debugging the display controller or testing display outputs, prepare for the following:
  • Enable modetest in menuconfig
  • Verify the connection status. You can find such information in the startup logs as follows.
    Figure 1. Start-up Logs
    Legend Description
    ① HDMI work status
    ② RGB2HDMI work status
    ③ MIPI work status
    ④ Display controller work status

Debug Display Function

To debug the display function, run the following command to verify the display functions and connection status. 

modetest -M starfive
Output examples:
  • Output 1:
    Legend Label Description
    ① possible crtcs Available Cathode Ray Tube Controller (CRTC) devices
    ② status Whether the display connector is connected or not
    ③ name The name (type) of the display connector
    ④ encoders The connected encoders
    ⑤ modes The supported display modes
    ⑥ value The Extended Display Identification Data (EDID) of the screen
  • Output 2:
    Legend Label Description
    ① id The CRTC 0x00000001 mentioned in possible crtcs, which means the CRTC is available for use.
    ② id The CRTC 0x00000002 mentioned in possible crtcs, which means the CRTC is available for use.
    Note: If the displayed CRTC is 0x00000003, both of the CRTCs are available for use.
  • Output 3:
    Figure 2. Debug Output 3
    Legend Description
    ① The CRTC and its connected plane

Test Display Outputs

To test a display output, run the following command:
modetest -M starfive -D 0 -a -s <Connector ID>@<CRTC ID>: <Resolution> -P <Plane ID>@<CRTC ID>: <Resolution>@<Format> -Ftiles
For example:
  • For HDMI output:
    modetest -M starfive -D 0 -a -s 116@31:1920x1080 -P 39@31:1920x1080@RG16 -Ftiles
  • For MIPI output:
    modetest -M starfive -D 0 -a -s 118@35:800x480 -P 74@35:800x480@RG16
  • For RGB2HDMI output:
    modetest -M starfive -D 0 -a -s 118@35:1920x1080 -P 74@35:1920x1080@RG16 -Ftiles
  • If your board is connected with both a MIPI and a RGB2HDMI output devices, the following commands show an example for testing on each of them.
    • For MIPI:
      modetest -M starfive -D 0 -a -s 120@35:800x480 -P 74@35:800x480@RG16
    • For RGB2HDMI:
      modetest -M starfive -D 0 -a -s 118@35:1920x1080 -P 74@35:1920x1080@RG16 -Ftiles