Additional steps for blacklisting compiled in kernel drivers

I am having a conflict with third party moxa driver mxupcie and the default linux 8250_moxa which is compiled in. I have been following [this](https://unix.stackexchange.com/questions/276392/how-to-block-drivers-built-into-kernel-i-e-drivers-who-are-not-a-module) thread but still having issues. -bash-4.2$ lspci -vvv -s8a:00.0 8a:00.0 Serial controller: Moxa Technologies Co Ltd CP-118EL-A (8-port RS-232/422/485 PCI Express Serial Board) (prog-if 02 ) Subsystem: Moxa Technologies Co Ltd CP-118EL-A (8-port RS-232/422/485 PCI Express Serial Board) Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR- Kernel modules: 8250_moxa, mxupcie There are quite a few symbols containing 8250 but looking through the source it appears that serial8250_init is the __init function for multiple serial drivers. I added the initcall_blacklist entry to my kernel parameters using the command below and rebooted but I am still seeing the same thing. grubby --update-kernel=ALL --args="initcall_blacklist=serial8250_init" After reboot I still see the same behavior -bash-4.2$ cat /proc/cmdline BOOT_IMAGE=/vmlinuz-4.9.220-rt143-RedHawk-7.5.5-trace root=/dev/mapper/vg00-root ro crashkernel=auto rd.md.uuid=2bc7cf35:ce34a47b:9688d2a0:1c0ea085 rd.lvm.lv=vg00/root rd.lvm.lv=vg00/swap rhgb quiet initcall_blacklist=serial8250_init I initially assumed that I chose the wrong __init function, which I guess I still might have, but looking at the System.map I can see that the symbol is still there, which I don't believe it should be. -bash-4.2$ cat /boot/System.map-uname -r |grep serial8250_init ffffffff813d81e0 T serial8250_init_port ffffffff81a0bc70 r __ksymtab_serial8250_init_port ffffffff81a288db r __kstrtab_serial8250_init_port ffffffff8202a6d2 t serial8250_init ffffffff820d4a20 t __initcall_serial8250_init6 I've never done this before, so I assume I am missing a step. What else do I need to do?