IQ-8275

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 verify whether the DisplayPort cable is connected, 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

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Debug the DisplayPort

​Debug the DisplayPort

Debug the DisplayPort