u-boot (forks) status

[asavah]

         - missing support for Rock64

Wrong there is support for rock64, you can build u-boot using evb-rk3328_defconfig both mainline and rockchip-uboot

What is the best u-boot fork/branch for Rock64 ?

I've been playing with all the forks you mention,
so far my conclusion is: ayufan-uboot FTW.

How many features/bugfixes are missing from u-boot upstream in rockchip-linux/u-boot fork and vice-versa ?

Ayufan's u-boot has gmac and efuse  support,
thus it is able to get mac address (actually it reads the serial and transforms it into a mac) from efuse and pass it to the kernel,
the others can not, thus on each reboot you'll get a random mac which sucks if you assign "static" ip to the board via your dhcp server.

Ayufan's u-boot has spl support for rk3328 - easier building, no need for crap rockchip binaries in order to prepare final u-boot img.
I haven't checked other fetures as I don't need them, I was having problems with emmc calibration on soft reboot
and I thought u-boot was to blame, so I decided to find out which fork is more stable, however the problem was in kernel's dtb,
I screwed it up while porting a patch from somewhere.

Is there any chance to that Rockchip joins u-boot upstream ?

This question is better asked at rockchip's github repo, however their devs are not responsive at all and their support sucks.