From: Nathan Chancellor <redacted>
Date: Wed, 31 Jul 2019 09:35:09 -0700

In file included from ../drivers/net/phy/mdio-octeon.c:14:
../drivers/net/phy/mdio-cavium.h:111:36: error: implicit declaration of function 'writeq'; did you mean 'writeb'? [-Werror=implicit-function-declaration]
  111 | #define oct_mdio_writeq(val, addr) writeq(val, (void *)addr)

One of the hi-lo, lo-hi writeq/readq headers has to be included.