Re: [PATCH] drm/amdgpu: Remove pci address checks from acpi_vfct_bios

[Alex Deucher <alexdeucher@gmail.com>]

On Mon, Mar 18, 2024 at 10:19 AM Kurt Kartaltepe <kkartaltepe@gmail.com> wrote:
>
> On Mon, Mar 18, 2024 at 6:37 AM Alex Deucher <alexdeucher@gmail.com> wrote:
> >
> > On Mon, Mar 18, 2024 at 4:47 AM Kurt Kartaltepe <kkartaltepe@gmail.com> wrote:
> > >
> > > These checks prevent using amdgpu with the pcie=assign-busses parameter
> > > which will re-address devices from their acpi values.
> > >
> > > Signed-off-by: Kurt Kartaltepe <kkartaltepe@gmail.com>
> >
> > This will likely break multi-GPU functionality.  The BDF values are
> > how the sbios/driver differentiates between the VFCT images.  If you
> > have multiple GPUs in the system, the driver won't be able to figure
> > out which one goes with which GPU an you may end up assigning the
> > wrong image to the wrong device.
> >
> > Alex
>
> The vendor and device portions must be correct in the existing
> kernels, so device type differentiation should already work without
> BDF values.
>
> So does that mean the concern is images are different for devices with
> the same vendor:device pairs? There are sites out there dedicated to
> dumping AMD's video roms which seem to suggest all discrete devices
> would be fine loading the same rom. Is there another platform you are
> thinking of where devices with the same vendor:device values would
> need different images?

That is incorrect.  The vbios images are board specific.  Using the
wrong image can cause a lot of problems.  The vbios exists to handle
board specific design variations (e.g., the number and type of display
connectors, the i2c/aux channel mappings, board specific clock and
voltage settings, etc.).  The PCI DID just indicates the chip used on
the board.  The actual board design varies with each AIB vendor (e.g.,
Sapphire and XFX both make 7900XTX boards, but they can have very
different configurations.

Alex

>
> (Sorry this is my first patch to the mailing list and I am replying
> with gmail, I hope it doesnt break things).
>
> --Kurt Kartaltepe