[PATCH v3 6/9] drm/amdgpu: Implement TTM handling for MMIO_REMAP placement

[Alex Deucher]

On Thu, Aug 28, 2025 at 5:33 AM Srinivasan Shanmugam
<srinivasan.shanmugam at amd.com> wrote:
>
> Implement TTM-level behavior for AMDGPU_PL_MMIO_REMAP so it behaves as a
> CPU-visible IO page:
>
> * amdgpu_evict_flags(): mark as unmovable
> * amdgpu_res_cpu_visible(): consider CPU-visible
> * amdgpu_bo_move(): use null move when src/dst is MMIO_REMAP
> * amdgpu_ttm_io_mem_reserve(): program base/is_iomem/caching using
>   the device's mmio_remap_* metadata
> * amdgpu_ttm_io_mem_pfn(): return PFN for the remapped HDP page
> * amdgpu_ttm_tt_pde_flags(): set AMDGPU_PTE_SYSTEM for this mem type
>
> v2:
> - Drop HDP-specific comment; keep generic remap (Alex).
>
> v3:
> - Fix indentation in amdgpu_res_cpu_visible (Christian).
> - Use adev->rmmio_remap.bus_addr for MMIO_REMAP bus/PFN calculations
>   (Alex).
>
> Cc: Christian König <christian.koenig at amd.com>
> Suggested-by: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 27ab4e754b2a..9211d250fcfb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -123,6 +123,7 @@ static void amdgpu_evict_flags(struct ttm_buffer_object *bo,
>         case AMDGPU_PL_GWS:
>         case AMDGPU_PL_OA:
>         case AMDGPU_PL_DOORBELL:
> +       case AMDGPU_PL_MMIO_REMAP:
>                 placement->num_placement = 0;
>                 return;
>
> @@ -447,7 +448,8 @@ bool amdgpu_res_cpu_visible(struct amdgpu_device *adev,
>                 return false;
>
>         if (res->mem_type == TTM_PL_SYSTEM || res->mem_type == TTM_PL_TT ||
> -           res->mem_type == AMDGPU_PL_PREEMPT || res->mem_type == AMDGPU_PL_DOORBELL)
> +           res->mem_type == AMDGPU_PL_PREEMPT || res->mem_type == AMDGPU_PL_DOORBELL ||
> +           res->mem_type == AMDGPU_PL_MMIO_REMAP)
>                 return true;
>
>         if (res->mem_type != TTM_PL_VRAM)
> @@ -538,10 +540,12 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
>             old_mem->mem_type == AMDGPU_PL_GWS ||
>             old_mem->mem_type == AMDGPU_PL_OA ||
>             old_mem->mem_type == AMDGPU_PL_DOORBELL ||
> +           old_mem->mem_type == AMDGPU_PL_MMIO_REMAP ||
>             new_mem->mem_type == AMDGPU_PL_GDS ||
>             new_mem->mem_type == AMDGPU_PL_GWS ||
>             new_mem->mem_type == AMDGPU_PL_OA ||
> -           new_mem->mem_type == AMDGPU_PL_DOORBELL) {
> +           new_mem->mem_type == AMDGPU_PL_DOORBELL ||
> +           new_mem->mem_type == AMDGPU_PL_MMIO_REMAP) {
>                 /* Nothing to save here */
>                 amdgpu_bo_move_notify(bo, evict, new_mem);
>                 ttm_bo_move_null(bo, new_mem);
> @@ -629,6 +633,12 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_device *bdev,
>                 mem->bus.is_iomem = true;
>                 mem->bus.caching = ttm_uncached;
>                 break;
> +       case AMDGPU_PL_MMIO_REMAP:
> +               mem->bus.offset = ((resource_size_t)mem->start << PAGE_SHIFT);
> +               mem->bus.offset += (resource_size_t)adev->rmmio_remap.bus_addr;

You can drop the casts here.  With that fixed this patch is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> +               mem->bus.is_iomem = true;
> +               mem->bus.caching = ttm_uncached;
> +               break;
>         default:
>                 return -EINVAL;
>         }
> @@ -646,6 +656,8 @@ static unsigned long amdgpu_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
>
>         if (bo->resource->mem_type == AMDGPU_PL_DOORBELL)
>                 return ((uint64_t)(adev->doorbell.base + cursor.start)) >> PAGE_SHIFT;
> +       else if (bo->resource->mem_type == AMDGPU_PL_MMIO_REMAP)
> +               return ((uint64_t)(adev->rmmio_remap.bus_addr + cursor.start)) >> PAGE_SHIFT;
>
>         return (adev->gmc.aper_base + cursor.start) >> PAGE_SHIFT;
>  }
> @@ -1355,7 +1367,7 @@ uint64_t amdgpu_ttm_tt_pde_flags(struct ttm_tt *ttm, struct ttm_resource *mem)
>
>         if (mem && (mem->mem_type == TTM_PL_TT ||
>                     mem->mem_type == AMDGPU_PL_DOORBELL ||
> -                   mem->mem_type == AMDGPU_PL_PREEMPT)) {
> +                   mem->mem_type == AMDGPU_PL_PREEMPT || mem->mem_type == AMDGPU_PL_MMIO_REMAP)) {
>                 flags |= AMDGPU_PTE_SYSTEM;
>
>                 if (ttm->caching == ttm_cached)
> --
> 2.34.1
>