And with a U-Boot based on f5c626c64874d6e1482edf4a76aa22e5e54be63d without my patches you see correct behavior?
The screen turning off issue was caused by a deployment script copying the wrong u-boot binary to the SD card! The patch does not introduce a regression on RPI 3 (tested before/after patch).
Once I switched over to the the real u-boot image the grub graphical font didn't load (irrespective of patch) I was able to fix this by changing the rpi_3_defconfig:
-CONFIG_OF_EMBED=y -CONFIG_DEFAULT_DEVICE_TREE="bcm2837-rpi-3-b" +CONFIG_OF_BOARD=y
I suspect my issues are to do with DTBs and that all these problems will go away once a single defconfig is available. The screen turning off issue I have no idea about but its from a much older version of u-boot and probably relates to something in the image I built.
Sorry for the noise - lets park this one.
Cheers, Geoff