How to port a SPI device on u-boot of RK3399Pro?

Hi. EveryOne.

I'm developing AI device with RK3399Pro and want to attach a SPI device.
The SPI device is successfully working on Kernel but not on u-boot.
Because of some reason, the SPI device should work on u-boot.
I developed SPI driver according to spi-howto.txt guideline. But the SPI is not working on u-boot.

But there are some strange status.
After RK3399Pro is rebooted (soft-reboot) with "reboot" command, the SPI device is working on u-boot.

So,  I want to know how to fix this problem.
If there are guideline to port a new spi device to u-boot of RK3399Pro, let me know.
Sample code is very helpful.

Thanks in advance.