6by9

I know nothing about how u-boot would be handling this. At one point I believe it used the bcm2708_fb mailbox calls, and those would potentially trash what had been set...

Forum thread locked with a link to here to avoid duplicated discussions.

Sorry, I have no idea how u-boot has set things up. You shouldn't have a rainbow screen on the primary monitor at that point though, as the simple framebuffer should...

> The VPU (and hence start.elf) has no way to prevent the ARM cores from accessing regions of memory, so that can't be the cause of what you are seeing....

> okay. do the vc/v3d drivers do any fiddling with the gpu to be able to write to the fdt-provided fb or does it just work, if you happen to...

``` # ./vcgencmd dispmanx_list display:0 format:XRGB8888 transform:0 layer:-127 800x600 src:0,0,800,600 dst:0,0,640,480 cost:742 lbm:10240 display:2 format:RGB565 transform:0 layer:-127 2x2 src:0,0,2,2 dst:100,0,600,600 cost:453 lbm:1024 ``` You have 2 displays configured. From your...

> There is only one screen. DPI -> TFP401-> LVDS driver-> display Then you've misconfigured the firmware. ``` dpi_group=2 dpi_mode=9 framebuffer_width=800 framebuffer_height=600 enable_dpi_lcd=1 ``` Do NOT set `hdmi_force_hotplug=1` as you're...

Thinking further, I'm not sure how you're expecting the DPI display to work when vc4 does take over - you appear to have no configuration that tells it to enable...

``` [ 5.470778] vc4-drm gpu: [drm] Cannot find any crtc or sizes [ 5.478622] vc4-drm gpu: [drm] Cannot find any crtc or sizes ``` Expected if you've let vc4 start....

Forum thread (such as it was) https://forums.raspberrypi.com/viewtopic.php?t=384108