[U-Boot] linux "coherent_pool" kernel parameter and u-boot

Hello u-boot list members, i have a problem with my arm64 odroid c2 board running some dvb-s2 usb cards. I had to increase the dma buffers for usb with kernel parameter "coherent_size=4M" to get them running. The default was 256kB. My question is, has this buffer to be defined or reserved in u-boot too ? From earlyer work with at91 i know that some adresses for kernel image and pool were be defined in u-boot config space. Can please someone explain how this works today on arm64 ?

Thanks Thomas