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

[t-erdmann]

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