Re: [PATCH 6/6] m68k/nommu: stop using GENERIC_IOMAP

[Arnd Bergmann]

On Mon, Mar 24, 2025, at 02:33, Greg Ungerer wrote:
> Hi Arnd,
>
> On 15/3/25 20:59, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@xxxxxxxx>
>> 
>> There is no need to go through the GENERIC_IOMAP wrapper for PIO on
>> nommu platforms, since these always come from PCI I/O space that is
>> itself memory mapped.
>> 
>> Instead, the generic ioport_map() can just return the MMIO location
>> of the ports directly by applying the PCI_IO_PA offset, while
>> ioread32/iowrite32 trivially turn into readl/writel as they do
>> on most other architectures.
>> 
>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
>
> With this applied this fails to build for me:
>
>    UPD     include/generated/utsversion.h
>    CC      init/version-timestamp.o
>    LD      vmlinux
> m68k-linux-uclibc-ld: drivers/pci/quirks.o: in function 
> `quirk_switchtec_ntb_dma_alias':
> quirks.c:(.text+0x23e4): undefined reference to `pci_iomap'
> m68k-linux-uclibc-ld: quirks.c:(.text+0x24fe): undefined reference to 
> `pci_iounmap'
> m68k-linux-uclibc-ld: drivers/pci/quirks.o: in function 
> `disable_igfx_irq':
> quirks.c:(.text+0x32f4): undefined reference to `pci_iomap'
> m68k-linux-uclibc-ld: quirks.c:(.text+0x3348): undefined reference to 
> `pci_iounmap'

Thanks for the report, I was able to reproduce the problem now
and applied the fixup below. I had tested m5475evb_defconfig earlier,
and that built cleanly with PCI enabled, but I had missed how
that still used GENERIC_IOMAP because it has CONFIG_MMU enabled.

Does this fixup work for you?

On a related note, I'm curious about how the MCF54xx chips are
used in practice, as I see that they are the only coldfire chips
with PCI and they all have an MMU. Are there actual users of these
chips that have PCI but choose not to use the MMU? 

      Arnd

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