FAQ
From Rockchip open source Document
How to select board config
DDR:
We use opensource idbloader(See Boot_option) on some chips (rk3036, rk3288) and its dmc driver can't support ddr-type autodetct, so the wrong ddr dts settings will make the board failed to enter u-boot.
PMIC:
PMIC setting usually doesn't matter in u-boot, but for the board with rk818, USB input current should be configured before enter u-boot.
Boot:
Some board have disable emmc in u-boot though the hardware actually have emmc, please note it. (firefly-rk3288)