Jetson TX2/28 Display debug

Get prepared

This section focuses on debug display driver issue on rel-28.x release.
Drivers of tegra display controller are under kernel source: https://developer.nvidia.com/embedded/downloads
Location:
For T210(TX1)
kernel/display/drivers/video/tegra/dc/
For T186(TX2). Note that TX2 still uses driver code of T210.
kernel/t18x/drivers/video/tegra/dc

Tips

• Print current mode in dc

sudo cat /sys/kernel/debug/tegradc.X/mode  #X=0,1,2.

• Print current mode in fbcon

sudo cat /sys/class/graphics/fb0/mode  #if more than one fb, just change the fbX to whatever you want.

• Capture edid

sudo cat /sys/kernel/debug/tegradc.X/edid  #X=0,1,2.

• Forcing edid

1. Prepare a known 256byte EDID.
2. set use_fallback = true; in tegra_edid_get_monspecs() under edid.c.
3. fill in the known EDID to default_720p_edid[256].

• If I hit underflow? (red screen or blank line flicker)

sudo cat /sys/kernel/debug/tegradc.0/stats
underflows: 35
underflows_a: 143
underflows_b: 0
underflows_c: 0

• Blank/Unblank window/display

sudo  echo 4 > /sys/class/graphics/fb0/blank  #blank display and power down
sudo  echo 1 > /sys/class/graphics/fb0/blank  #blank display and show the background color
sudo  echo 0 > /sys/class/graphics/fb0/blank

• Other issues

dmesg |grep tegradc #print out display kernel related message

Issues

• HDMI
  • Display is not be able to up. Moreover, system is not able to up.(Fixed after rel-28.2)
    • https://devtalk.nvidia.com/default/topic/1003956/jetson-tx2/tx2-not-booting-up-with-hdmi-connected/post/5160211/#5160211