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Debug the DisplayPort

  • You must enable SSH to access your host device. For instructions, see Sign in using SSH.
  • To mount the debugfs file system to access the debugfs details of the display subsystem, run the following commands:
mount -o remount,rw /

mount -t debugfs none /sys/kernel/debug
View the selected DisplayPort To check the selected DisplayPort, run the following command: 
cat /sys/kernel/debug/dri/0/DP-1/dp_debug
Sample output 
name = msm_dp
drm_dp_link
        rate = 270000
        num_lanes = 4
        capabilities = 1
dp_panel_info:
        active = 3840x2160
        back_porch = 80x23
        front_porch = 48x3
        sync_width = 32x5
        active_low = 0x0
        h_skew = 0
        refresh rate = 30
        pixel clock khz = 262750
        bpp = 30
dp_link:
        test_requested = 512
        num_lanes = 4
        bw_code = 10
        lclk = 270000000
        v_level = 1
        p_level = 0
View the status of DisplayPort cable To check the DisplayPort connection, run the following command: 
cat /sys/class/drm/card0-DP-1/status
Sample output 
Connected
Check the extended display identification data (EDID) mode To check for the EDID mode of the DisplayPort connected, run the following command: 
cat /sys/class/drm/card0-DP-1/modes
Sample output 
3840x2160
2048x1080