[PATCH] drm/amdgpu: Set ttm caching flags during bo allocation

[Das, Nirmoy]

Thanks for the detailed commit message :)

Acked-by: Nirmoy Das <nirmoy.das at amd.com>

On 6/29/2021 1:15 AM, Oak Zeng wrote:
> The ttm caching flags (ttm_cached, ttm_write_combined etc) are
> used to determine a buffer object's mapping attributes in both
> CPU page table and GPU page table (when that buffer is also
> accessed by GPU). Currently the ttm caching flags are set in
> function amdgpu_ttm_io_mem_reserve which is called during
> DRM_AMDGPU_GEM_MMAP ioctl. This has a problem since the GPU
> mapping of the buffer object (ioctl DRM_AMDGPU_GEM_VA) can
> happen earlier than the mmap time, thus the GPU page table
> update code can't pick up the right ttm caching flags to
> decide the right GPU page table attributes.
>
> This patch moves the ttm caching flags setting to function
> amdgpu_vram_mgr_new - this function is called during the
> first step of a buffer object create (eg, DRM_AMDGPU_GEM_CREATE)
> so the later both CPU and GPU mapping function calls will
> pick up this flag for CPU/GPU page table set up.
>
> Signed-off-by: Oak Zeng <Oak.Zeng at amd.com>
> Suggested-by: Christian Koenig <Christian.Koenig at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      | 4 ----
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 5 +++++
>   2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 6297363..93acf6f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -607,10 +607,6 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_device *bdev,
>   
>   		mem->bus.offset += adev->gmc.aper_base;
>   		mem->bus.is_iomem = true;
> -		if (adev->gmc.xgmi.connected_to_cpu)
> -			mem->bus.caching = ttm_cached;
> -		else
> -			mem->bus.caching = ttm_write_combined;
>   		break;
>   	default:
>   		return -EINVAL;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index a52e17e..6cb66eb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -454,6 +454,11 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>   	if (i == 1)
>   		mem->placement |= TTM_PL_FLAG_CONTIGUOUS;
>   
> +	if (adev->gmc.xgmi.connected_to_cpu)
> +		mem->bus.caching = ttm_cached;
> +	else
> +		mem->bus.caching = ttm_write_combined;
> +
>   	atomic64_add(vis_usage, &mgr->vis_usage);
>   	mem->mm_node = nodes;
>   	return 0;