How to Config Multi-Display

Introductory

RSB-4710 surport 4 display ports : eDP、LVDS（mipi to LVDS）、HDMI、DP （DP to HDMI）. Only two ports work at the same time .

You can config Multi-Display to eDP + HDMI 、eDP + LVDS、LVDS + HDMI 、eDP + DP、LVDS + DP、HDMI + DP.

NOTE：

Android distinguish the primary and the extend screen. 

Contents

 [hide] 

• 1 Enter U-boot interrupt mode
• 2 eDP + HDMI
• 3 eDP + LVDS
• 4 LVDS + HDMI
• 5 eDP + DP
• 6 LVDS + DP
• 7 HDMI + DP
• 8 Default Support Display

Enter U-boot interrupt mode

Connect device to debug port, and open debug console. See more : How_to_debug.

Press "ctrl + c" key before power up the device, until get the following information on debug console : 

Hit any key to stop autoboot: 0
=> <INTERRUPT>
=>

Then you can input the following cammand to config Multi-Display.

eDP + HDMI

setenv prmry_screen edp-1920x1080
setenv extend_screen hdmi-default
saveenv
reset

 

or

setenv prmry_screen hdmi-default
setenv extend_screen edp-1920x1080
saveenv
reset

eDP + LVDS

setenv prmry_screen edp-1920x1080
setenv extend_screen lvds-g070vw01
saveenv
reset

or

setenv prmry_screen lvds-g070vw01
setenv extend_screen edp-1920x1080 
saveenv
reset

 

LVDS + HDMI

setenv prmry_screen hdmi-default
setenv extend_screen lvds-g070vw01
saveenv
reset

or

setenv prmry_screen lvds-g070vw01
setenv extend_screen hdmi-default
saveenv
reset

eDP + DP

setenv prmry_screen edp-1920x1080
setenv extend_screen dp-default
saveenv
reset

 

or

setenv prmry_screen dp-default
setenv extend_screen edp-1920x1080
saveenv
reset

 

LVDS + DP

setenv prmry_screen dp-default
setenv extend_screen lvds-g070vw01
saveenv
reset

or

setenv prmry_screen lvds-g070vw01
setenv extend_screen dp-default 
saveenv
reset

 

HDMI + DP

setenv prmry_screen hdmi-default
setenv extend_screen dp-default
saveenv
reset

or

setenv prmry_screen dp-fefault
​setenv extend_screen hdmi-default
saveenv
reset

Default Support Display

Port	RSB4710
edp	edp-1920x1080 edp-1366x768
lvds	lvds-g070vw01 lvds-g150xgel05 lvds-g215hvn01
hdmi	hdmi-default
dp	dp-default

NOTE : 

1. The name of the panel must begin with "edp-"、"lvds-" 、"hdmi-"  or “dp-”.

And it can be found in "kernel/include/dt-bindings/display/screen-timing/{LCDNAME}.dtsi" like :

lvds_g070vw01: lvds-g070vw01

2. If there is no configuration, you will get default setting :

hdmi-default  and dp-default as default setting.

3. Check your configuration in Terminal or debug console.

cat /proc/cmdline
... prmry_screen=hdmi-default extend_screen=dp-default

LVDS Name	Resolution
lvds-g070vw01	800x480
lvds-g150xgel05	1024x768
lvds-g215hvn01	1920x1080

Using envtools in Debian/Android

Using envtools to setup envs in Debian/Android OS is very similar in uboot.

Take “eDP+HDMI”for example :

In uboot	In Debian/Android
setenv prmry_screen hdmi-default	fw_setenv prmry_screen hdmi-default
setenv extend_screen edp-1920x1080	fw_setenv extend_screen edp-1920x1080
saveenv
reset	reboot

Note :

The tool "fw_setenv" will save envs automatically in Debian/Android OS, so it isn't necessary to saveen manually.

Check current setting：

root@linaro-alip:~# cat /proc/cmdline
storagemedia=emmc androidboot.storagemedia=emmc androidboot.mode=normal  androidboot.verifiedbootstate=orange androidboot.slot_suffix= androidboot.serialno=a2fc4116ad6b2c4f  rw rootwait earlycon=uart8250,mmio32,0xff180000 swiotlb=1 console=ttyS0,115200 root=PARTUUID=614e0000-0000 rootfstype=ext4 coherent_pool=1m quiet board_info=9 prmry_screen=hdmi-default extend_screen=lvds-g070vw01
root@linaro-alip:~#

Configurate Multi-Display of differnt resolutions in Duplicate mode

If Multi-Display has differnt resolution in duplicate mode, you can see all view on the screen of big resolution and the view in the top left corner on the screen of small resolution.

If you want to the same view on the two screens. Using xrandr to configurate Multi-Display of differnt resolutions in Duplicate mode in Debian OS.

Take “LVDS (1024x768) + HDMI (1920x1080)”for example:

 xrandr --output HDMI-1 --scale-from 1024x768
or
 xrandr --output LVDS-1 --scale-from 1920x1080