Re: [PATCH 01/11] drm/amdgpu: Align amdgpu_gtt_mgr entries to TLB size on Tahiti

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

On 4/23/26 03:16, Timur Kristóf wrote:
> The TLB is organized in groups of 8 entries, each one is 4K.
> On Tahiti, the HW requires these GART entries to be 32K-aligned.
> 
> This fixes a VCE 1 firmware validation failure that can happen
> after suspend/resume since we use amdgpu_gtt_mgr for VCE 1.
> 
> Fixes: 698fa62f56aa ("drm/amdgpu: Add helper to alloc GART entries")
> Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> index 9b0bcf6aca445..673e9e08c66a0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> @@ -198,12 +198,19 @@ int amdgpu_gtt_mgr_alloc_entries(struct amdgpu_gtt_mgr *mgr,
>  				 u64 num_pages,
>  				 enum drm_mm_insert_mode mode)
>  {
> +	u32 alignment = 0;
>  	struct amdgpu_device *adev = container_of(mgr, typeof(*adev), mman.gtt_mgr);
>  	int r;

Only a nit, but reverse xmas tree order please for variable declarations.

>  
> +	/* Align to TLB size on Tahiti */

Oh that needs improvement.

Maybe something like /* Align to TLB L2 cache entry size to work around V bit HW bug */

Mostly nobody will know what that "V bit HW bug" is, but at least AMD people can search for that in the HW docs.

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

Thanks,
Christian.

> +	if (adev->asic_type == CHIP_TAHITI) {
> +		alignment = 32 * 1024 / AMDGPU_GPU_PAGE_SIZE;
> +		num_pages = ALIGN(num_pages, alignment);
> +	}
> +
>  	spin_lock(&mgr->lock);
>  	r = drm_mm_insert_node_in_range(&mgr->mm, mm_node, num_pages,
> -					0, GART_ENTRY_WITHOUT_BO_COLOR, 0,
> +					alignment, GART_ENTRY_WITHOUT_BO_COLOR, 0,
>  					adev->gmc.gart_size >> PAGE_SHIFT,
>  					mode);
>  	spin_unlock(&mgr->lock);