Re: [PATCH 1/7] drm/amdgpu/gmc: Fix AMDGPU_GART_PLACEMENT_LOW to not overlap with VRAM

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

On 4/16/26 22:26, Timur Kristóf wrote:
> When the GART placement is set to AMDGPU_GART_PLACEMENT_LOW:
> Make sure that GART does not overlap with VRAM when
> VRAM is configured to be in the low address space.
> 
> Solve this according to the following logic:
> - When GART fits before VRAM, use zero address for GART
> - Otherwise, put GART after the end of VRAM, aligned to 4 GiB
> 
> Previously, I had assumed this was not possible
> so it was OK to not handle it, but now we got a report
> from a user who has a board that is configured this way.
> 
> Fixes: 917f91d8d8e8 ("drm/amdgpu/gmc: add a way to force a particular placement for GART")
> Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> index 1daf2546d3b26..b454b463bcb2e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
> @@ -314,7 +314,10 @@ void amdgpu_gmc_gart_location(struct amdgpu_device *adev, struct amdgpu_gmc *mc,
>  		mc->gart_start = max_mc_address - mc->gart_size + 1;
>  		break;
>  	case AMDGPU_GART_PLACEMENT_LOW:
> -		mc->gart_start = 0;
> +		if (size_bf >= mc->gart_size)
> +			mc->gart_start = 0;
> +		else
> +			mc->gart_start = ALIGN(mc->fb_end, four_gb);
>  		break;
>  	case AMDGPU_GART_PLACEMENT_BEST_FIT:
>  	default: