linux-kernel - Question about PCI I/O space in ARM64

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Message-ID: <56F209A9.4040304@huawei.com>
Date:	Wed, 23 Mar 2016 11:12:41 +0800
From:	Kefeng Wang <wangkefeng.wang@...wei.com>
To:	<linux-pci@...r.kernel.org>, <catalin.marinas@....com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	<wangkefeng.wang@...wei.com>
CC:	Gabriele Paoloni <gabriele.paoloni@...wei.com>,
	Arnd Bergmann <arnd@...db.de>, <linux-kernel@...r.kernel.org>,
	<Lorenzo.Pieralisi@....com>, Linuxarm <linuxarm@...wei.com>,
	Zhou Wang <wangzhou1@...ilicon.com>
Subject: Question about PCI I/O space in ARM64

Hi all，

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.

Thanks
Kefeng