Is it possible to use Rockchip chips without blobs?

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My board is Firefly ROC-RK3308B-CC-Plus based on Rockchip RK3308 SoC.
Do I really need rk3308_ddr_589MHz_uart4_m0_v2.07.bin from bin/rk33/ directory of this repo to get it worked?
I'm trying to replace this blob by U-Boot TPL as the official wiki suggests, but have no success.

First, how it works:

#!/bin/sh

./tools/mkimage -n rk3308 -T rksd -d bin/rk33/rk3308_ddr_589MHz_uart4_m0_v2.07.bin idbloader.img # Blob =(
cat Firefly_Linux_SDK/rk3308_linux_release_v1.5.0a_20221212/u-boot/spl/u-boot-spl.bin >> idbloader.img
cp Firefly_Linux_SDK/rk3308_linux_release_v1.5.0a_20221212/u-boot/u-boot.img .
rkdeveloptool db Firefly_Linux_SDK/rk3308_linux_release_v1.5.0a_20221212/rkbin/rk3308_loader_uart4_v2.07.139.bin # Temporary loader, compiled it early
sleep 1
rkdeveloptool wl 0x40 idbloader.img
sleep 1
rkdeveloptool wl 0x4000 u-boot.img
sleep 1
rkdeveloptool rd

Then I replaced the first two lines with this:

./tools/mkimage -n rk3308 -T rksd -d Firefly_Linux_SDK/rk3308_linux_release_v1.5.0a_20221212/u-boot/tpl/u-boot-tpl-dtb.bin idbloader.img
cat Firefly_Linux_SDK/rk3308_linux_release_v1.5.0a_20221212/u-boot/spl/u-boot-spl-dtb.bin >> idbloader.img

And there is no any output to serial console now.

What could I missed?

Could you also take me advice which U-Boot codebase should I use, U-Boot official or the rockchip-linux fork? It seems that both support my board and SoC.