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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 16 Aug 2018 23:10:33 +0200
Message-ID: <CAK8P3a2vAMzL22ds=kM1WRZgATzOrAz_y8Yk6edqJTVRJJFydw@mail.gmail.com>
Subject: Re: how to fix acpi_pci_root_remap_iospace?
To:     Tony Luck <tony.luck@intel.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        jchandra@broadcom.com, Sinan Kaya <okaya@codeaurora.org>,
        Tomasz Nowicki <tn@semihalf.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Boris Brezillon <boris.brezillon@bootlin.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>
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On Thu, Aug 16, 2018 at 10:45 PM Luck, Tony <tony.luck@intel.com> wrote:
>
> Bjorn,
>
> Back in commit:
>
>   0a70abb38062 ("PCI/ACPI: Support I/O resources when parsing host bridge resources")
>
> we added acpi_pci_root_remap_iospace().  On ia64 this was a no-op because ia64
> didn't define PCI_IOBASE, so the entire body of the function was skipped.
>
> But in the current merge window commit:
>
>   0bbf47eab469 ("ia64: use asm-generic/io.h")
>
> ended up defining PCI_IOBASE for us, and now we die horribly
> in early boot with:
>
>   kernel BUG at lib/ioremap.c:72!

Ah, that explains it. I'm sorry for causing you trouble here, and glad
you figured out the cause.

> Is PCI_IOBASE the right thing to check for to decide whether
> acpi_pci_root_remap_iospace() needs to do anything?
>
> The ugly fix would be:

Another way would be to add

 #include <asm-generic/io.h>
+#undef PCI_IOBASE

in your asm/io.h. This is about as ugly as the your version, but
it would be local to ia64 ;-)

      Arnd