Yocto. How to keep u-boot splash screen and then how to keep kernel splash screen on

Question

I am porting Yocto into my board. I wrote u-boot & kernel graphics drivers for my display. Everything works fine. The only problem I have is:

• u-boot splash screen is displayed for a while when kernel starts to load the screen goes blank
• then the kernel splash screen appears for a while, but the screen goes blank until Weston is loaded.

Is it possible to prevent the screen from going blank?

Answer 1

In short, yes, it is possible, but unfortunately, it greatly depends on your hardware and the u-boot and kernel versions.

I did this before for the beagle bone black, and the solution involved:

• My u-boot was from 2017 and used a legacy framebuffer (da8xx-fb.c). The corresponding driver un-initialized the LCD, so the display lost its clock afterward. I needed to patch u-boot to leave the LCD available.
• The kernel did a 'reset on init' for the LCD driver, but luckily, TI has a hint for the device tree suppressing this (ti,no-reset-on-init)
• The kernel uses DRM, but u-boot uses a framebuffer, so I had to set up the simple framebuffer until the DRM driver was active (https://www.kernel.org/doc/Documentation/devicetree/bindings/display/simple-framebuffer.txt)