Rock/display

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The cpu of Radxa Rock - RK3188 has two LCD controllers, LCD0 and LCD1. On RR, LCD1 is connected to HDMI and LCD0 is connect to AV out and the LCD0 signal are also exported on the extension header.

There is some sysfs interface exported to control the display related stuff. The following should work on both Android and Linux.

set display scale

   root@radxa:~# cd /sys/devices/platform/rk-fb/graphics/fb0
   root@radxa:/sys/devices/platform/rk-fb/graphics/fb0# cat scale
   xscale=95 yscale=95
   root@radxa:/sys/devices/platform/rk-fb/graphics/fb0# echo xscale=100 > scale     
   root@radxa:/sys/devices/platform/rk-fb/graphics/fb0# echo yscale=100 > scale     
   root@radxa:/sys/devices/platform/rk-fb/graphics/fb0# cat scale
   xscale=100 yscale=100

set HDMI output mode

   root@radxa:~# cd /sys/class/display/display0.HDMI

you can see supported output modes by the following commands:

   root@radxa:/sys/class/display/display0.HDMI# cat modes 
   1920x1080p-60
   1920x1080p-50
   1280x720p-60
   1280x720p-50
   720x576p-50
   720x480p-60

check out the current display mode

   root@radxa:/sys/class/display/display0.HDMI# cat mode
   1280x720p-60

It's 720p@60hz

change the mode to 1080p@60hz

   root@radxa:/sys/class/display/display0.HDMI# echo 1920x1080p-60 > mode