Question about PCI I/O space in ARM64

From: Kefeng Wang
Date: Tue Mar 22 2016 - 23:14:57 EST

Hi allï

If no pci, the PCI I/O space(16M) is mapped into an irrelevant mem space(right ?), not a right IO space,
that is, no one call pci_remap_iospace() to remap the memory mapped I/O space, once driver
like f71805f loaded, write value to IO space(see f71805f_init->f71805f_find->superio_enter->outb),
we met following oops,
Unable to handle kernel paging request at virtual address ffffffbffee0002e
pgd = ffffffc1d68d4000
[ffffffbffee0002e] *pgd=0000000000000000, *pud=0000000000000000
Internal error: Oops: 94000046 [#1] PREEMPT SMP
Modules linked in: f71805f(+) hwmon
CPU: 3 PID: 1659 Comm: insmod Not tainted 4.5.0+ #88
Hardware name: linux,dummy-virt (DT)
task: ffffffc1f6665400 ti: ffffffc1d6418000 task.ti: ffffffc1d6418000
PC is at f71805f_find+0x6c/0x358 [f71805f]

I am not clear about PCI I/O, but if this is indeed a bug, how to solve this issue,
any advice will be appreciated.