drm/amdgpu: set snoop bit in pde/pte entries for A+A

Page tables in vram mapping to cpu is changed from uncached to
cached in A+A, the snoop bit in VM_CONTEXTx_PAGE_TABLE_BASE_ADDR/
PDE0s/PDE1s/PDE2s/PTE.TFs has to be set so gpuvm walker snoop
page table data out of CPU cache.
Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -1432,6 +1432,10 @@ uint64_t amdgpu_ttm_tt_pde_flags(struct ttm_tt *ttm, struct ttm_resource *mem)
 			flags |= AMDGPU_PTE_SNOOPED;
 	}
 
+	if (mem && mem->mem_type == TTM_PL_VRAM &&
+			mem->bus.caching == ttm_cached)
+		flags |= AMDGPU_PTE_SNOOPED;
+
 	return flags;
 }