raspberry pi 4 dual screens

[maw140]

Hello wondering if anyone can offer assistance. Got raspberrypi up and running single screen. Added second but all that comes up is the rainbow splash on second screen. Installed xranr and tried some things in /boot/config.txt without any luck. Assume it's something simple but cannot find the answer anywhere. Booted up a NOOBS install and both screens work. Cannot find where they have stuck the config for this to copy across through. Any help would be appreciated.

[maw140]

Just an update I addded :

dispmax display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

To /boot/config.txt and managed to get both monitors up in mirroring mode.

Just need them in extended mode to act as one monitor.

xrandr shows following so not as HDMI0 HDMI 1:
Failed to get size of gamma for output default
Screen 0: minimum 1680 x 1050, current 1680 x 1050, maximum 1680 x 1050
default connected 1680x1050+0+0 0mm x 0mm
1680x1050 0.00*

Next i went off to X11 and added to 99-fbturbo.conf:

Section "Device"
Identifier "Allwinner A10/A13 FBDEV"
Driver "fbturbo"
Option "fbdev" "/dev/fb0"
Option "SwapbuffersWait" "true"

EndSection

Section "Monitor"
Identifier "HDMI0"
Option "Primary" "True"
EndSection

Section "Monitor"
Identifier "HDMI1"
Option "LeftOf" "HDMI0"
EndSection

Section "Screen"
Identifier "screen1"
Device "Allwinner A10/A13 FBDEV"
Monitor "HDMI0"
#SubSection "Display"
#Depth 24
#Modes "1680x1050" "1680x1050" #the resolutions of your monitors
#Virtual 3360 1050
#EndSubSection
EndSection


Section "ServerLayout"
Identifier "default"
Screen 0 "screen1" 0 0
EndSection


However still no luck. Anyone help on this?

[miloc]

Hi,

I am experiencing the same issue. With the default configuration I got rainbow screen over the second hdmi output, then with this /boot/config.txt

$this->bbcode_second_pass_code('', '# See /boot/overlays/README for all available options

gpu_mem=64
initramfs initramfs-linux.img followkernel

# uncomment to force a console size. By default it will be display's size minus
# overscan.
framebuffer_width=1920
framebuffer_height=1080
disable_overscan=1
dtoverlay=vc4-kms-v3d-pi4
')

I get mirror screens.

This is my xrandr output.

$this->bbcode_second_pass_code('', '$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected 1920x1080+0+0 0mm x 0mm
1920x1080 0.00* ')

Any help would be appreciated.