Re: [PATCH 1/3] drm/amdgpu: reserve 64M stolen memory for Apple 5K iMac

["Christian König" <christian.koenig@amd.com>]

On 10/26/26 23:46, Richard Lane wrote:
> Apple 27" 5K iMacs report a single 2560x2880 tile (28.125 MiB) in
> VIEWPORT_SIZE while scanning out up to 64 MiB across the relocated EFI
> framebuffer.
> 
> Override the stolen VGA memory allocation size to 64 MiB when matching
> PCI_VENDOR_ID_APPLE with a 2560x2880x4 viewport size to prevent
> framebuffer corruption during boot handover.

Hacks like those are usually a big no-go.

Why is that framebuffer handling not working with DC out of the box?

Regards,
Christian.

> 
> Signed-off-by: Richard Lane <richardlanedev@gmail.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> index 4204c3c750a8..8b196fbfa724 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> @@ -1232,7 +1232,15 @@ void amdgpu_gmc_init_vga_resv_regions(struct amdgpu_device *adev)
>         } else {
>                 size = amdgpu_gmc_get_vbios_fb_size(adev);
> 
> -               if (adev->mman.keep_stolen_vga_memory)
> +               /*
> +                * Apple 5K iMacs report one 2560x2880 tile in VIEWPORT_SIZE
> +                * while scanning out up to 64M across the relocated EFI
> +                * framebuffer.
> +                */
> +               if (adev->pdev->subsystem_vendor == PCI_VENDOR_ID_APPLE &&
> +                   size == (2560 * 2880 * 4))
> +                       size = 64U * 1024 * 1024;
> +               else if (adev->mman.keep_stolen_vga_memory)
>                         size = max(size, (unsigned)AMDGPU_VBIOS_VGA_ALLOCATION);
>         }
> 
> --
> 2.55.0