RPi B+ Stuck At Rainbow, No UART Output

[173210]

Followed https://dri.freedesktop.org/wiki/VC4/, and used vc4_kms_v3d branch (5e0242f), but I had no luck.
I wrote cmdline.txt as the following but it has no UART output.

cma=256M@512M console=ttyAMA0,115200 kgdboc=ttyAMA0,115200

config.txt only contains avoid_warnings=2\n.
The firmware is up-to-date (e0fedf15518eef8a56f41113abd5ec8171e3981c), and has no additional bootloader such as Das U-Boot.

I also confirmed rpi-4.4.y(5bc0a41) works with the above configuration, but doesn't have DRM.
Any idea?

[anholt]

The intent wasn't for you to use the vc4_kms_v3d branch. I've rewritten the instructions to hopefully be clearer.

[173210]

Thanks. I'll close this issue.