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SubjectRe: [PATCH V2 2/2] efi/fb: Convert PCI bus address to resource if translated by the bridge
On 2018-06-25 04:20, Ard Biesheuvel wrote:
> On 22 June 2018 at 21:29, Ard Biesheuvel <ard.biesheuvel@linaro.org>
> wrote:
>> On 22 June 2018 at 20:30, Sinan Kaya <okaya@codeaurora.org> wrote:
>>> On 6/22/2018 2:01 PM, Ard Biesheuvel wrote:
>>>>> Yes, it is part of the PCI I/O protocol definition. FrameBufferBase
>>>>> is
>>>>> described as
>>>>>
>>>>> """
>>>>> Base address of graphics linear frame buffer. Info contains
>>>>> information required to allow software to draw directly to the
>>>>> frame buffer without using Blt().Offset zero in
>>>>> FrameBufferBase represents the upper left pixel of the
>>>>> display.
>>>>> """
>>>> I just tried AMD Radeon and NVidia graphics cards on a system with
>>>> non-1:1 mapped MMIO windows, and in both cases, the GOP protocol
>>>> structure is populated correctly, i.e., using the CPU address not
>>>> the
>>>> PCIe address.
>>>>
>>>> EDK2 only recently gained support for MMIO translation in the host
>>>> bridge driver, so I so wonder if this is a platform issue rather
>>>> than
>>>> a driver issue. It may be worth a try to dump the results of
>>>> GetBarAttributes() of all PCI I/O protocol instances (either in UEFI
>>>> or in the stub), to double check that the correct values are
>>>> returned.
>>>>
>>>
>>> Thanks for checking out other platforms. I'll mark the issue as a
>>> BIOS
>>> issue and bounce your feedback to the BIOS provider.
>>>
>>
>> I screwed up my testing, unfortunately. Both the public AMD GOP driver
>> I tried, and the Nvidia GT218 under x86 emulation break when using
>> MMIO translation. However, GraphicsOutputDxe in the EDK2 tree gets it
>> right, and uses PciIo->GetBarAttributes() to get the address of the
>> framebuffer region, which will return the CPU address not the PCI
>> address.
>>
>>> Let's hold onto this patch for the moment.
>>>
>>
>> Yes. I'd like to get this resolved as well, but if the drivers are
>> dereferencing BAR values as CPU addresses, this is unlikely to be the
>> only thing that is broken under outbound translation.
>
> Note that this was fixed fairly recently in EDK2, so BIOS vendors
> providing UEFI firmware for ARM platforms with outbound MMIO
> translation should probably incorporate this EDK2 patch
>
> commit dc080d3b61e570e7a3163fc24afa6f8388d0c0bf
> Author: Heyi Guo <heyi.guo@linaro.org>
> Date: Thu Feb 8 11:13:27 2018 +0800
>
> MdeModulePkg/PciBus: return CPU address for GetBarAttributes
>
> According to UEFI spec 2.7, PciIo->GetBarAttributes should return
> host
> address (CPU view ddress) rather than device address (PCI view
> address), and
> device address = host address + address translation offset,
> so we subtract translation from device address before returning.
>
> Note that this is not the only MMIO translation related change made by
> Heyi Guo to the generic PCI host bridge and bus drivers, but given
> that those did not support MMIO translation at all, I take it your
> affected platforms will already have their own changes to accommodate
> this.

Platform has been doing mmio translation for quite a while. Because all
accesses go through pci io protocol, the rest of the UEFI never needed
to be aware of bar address or do direct access.

This is the first time I hear of direct access. Maybe, GOP is a special
case.

I started copying your response to the bios vendor.

They are probably missing that patch. I will pass it along.

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