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SubjectRe: [PATCH V2 00/23] MMCONFIG refactoring and support for ARM64 PCI hostbridge init based on ACPI
From
> On Monday 21 December 2015, Tomasz Nowicki wrote:
>> On 21.12.2015 13:10, Lorenzo Pieralisi wrote:
>> > On Fri, Dec 18, 2015 at 06:56:39PM +0000, okaya@codeaurora.org wrote:
>
>> >> I have multiple root ports with the same IO port configuration in the
>> >> current ACPI table.
>> >>
>> >> Root port 0 = IO range 0x1000-0x10FFF
>> >> Root port 1 = IO range 0x1000-0x10FFF
>> >> Root port 2 = IO range 0x1000-0x10FFF
>> >
>> > It is fine. You end up mapping for each of those a 4k window of the
>> > virtual address space allocated to IO and that's what you will have in
>> > the kernel PCI resources (not in the HW BARs though). If that was a
>> problem
>> > it would be even for the current DT host controllers eg:
>> >
>> > arch/arm64/boot/dts/apm/apm-storm.dtsi
>> >
>> > it should not be (again I will let Arnd comment on this since he may
>> be
>> > aware of issues encountered on other arches/platforms).
>> >
>>
>> Root port 0 = IO range 0x1000-0x10FFF
>> Root port 1 = IO range 0x1000-0x10FFF
>> Root port 2 = IO range 0x1000-0x10FFF
>>
>> If above ranges are mapped into different CPU windows, then yes, it is
>> fine.
>
> Ideally, they should all be the same CPU address so we only have to map
> the window
> once, each device gets an address below 64K, and you can have legacy port
> numbers
> (below 4K) on any bus, which is required to make certain GPUs work.
>
> I haven't actually seen anyone do that on ARM though, every implementation
> so
> far has a separate mapping per host bridge, and we can cope with that too,
> and we can live with either overlapping bus addresses or unique bus
> addresses,
> any of them can be expressed by the PCI core in Linux, we just have to
> make sure
> that we correctly translate the firmware tables into our internal
> structures.
>
> Arnd
> --
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>

Thanks, I won't be touching the acpi tables then and I will assume the
hack had a problem. It was trying to remap the io range of the second root
port to the first port io address map.

I was getting a warning from resource.c

Btw, when I tested the io ranges before, kernel didn't accept anything
below 1k like 0. That is why my range starts at 1k.



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