aux->drm_dev in drm_dp_aux_register() is NULL when called from cdns-dp-core.c
during boot, we hit a WARN_ON() and see a stack trace on v5.15 based kernels:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3f3a6524f6065fd3d130515e012f63eac74d96da should describe the issue better. It doesn't seem to critical, but it's at least an indication that
drm_dp_aux_register() isn't use as intended in our dp drm driver.
Should we ask the author whether he's still working on it and can update? see https://lore.kernel.org/linux-arm-kernel/cover.1590982881.git.Sandor.firstname.lastname@example.org/