drm/amdgpu: add support for extended stolen vga memory

This will allow us to split the allocation for systems
where we have to keep the stolen memory around to avoid
S3 issues.  This way we don't waste as much memory and
still avoid any screen artifacts during the bios to
driver transition.
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h

@@ -215,6 +215,8 @@ struct amdgpu_gmc {
 	bool			prt_warning;
 	uint64_t		stolen_vga_size;
 	struct amdgpu_bo	*stolen_vga_memory;
+	uint64_t		stolen_extended_size;
+	struct amdgpu_bo	*stolen_extended_memory;
 	bool			keep_stolen_vga_memory;
 	uint32_t		sdpif_register;
 	/* apertures */

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

@@ -1915,7 +1915,7 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 	uint64_t gtt_size;
 	int r;
 	u64 vis_vram_limit;
-	void *stolen_vga_buf;
+	void *stolen_vga_buf, *stolen_extended_buf;
 
 	mutex_init(&adev->mman.gtt_window_lock);
 
@@ -1985,6 +1985,13 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 				       &stolen_vga_buf);
 	if (r)
 		return r;
+	r = amdgpu_bo_create_kernel_at(adev, adev->gmc.stolen_vga_size,
+				       adev->gmc.stolen_extended_size,
+				       AMDGPU_GEM_DOMAIN_VRAM,
+				       &adev->gmc.stolen_extended_memory,
+				       &stolen_extended_buf);
+	if (r)
+		return r;
 
 	DRM_INFO("amdgpu: %uM of VRAM memory ready\n",
 		 (unsigned) (adev->gmc.real_vram_size / (1024 * 1024)));
@@ -2041,11 +2048,13 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
  */
 void amdgpu_ttm_late_init(struct amdgpu_device *adev)
 {
-	void *stolen_vga_buf;
+	void *stolen_vga_buf, *stolen_extended_buf;
 
 	/* return the VGA stolen memory (if any) back to VRAM */
 	if (!adev->gmc.keep_stolen_vga_memory)
 		amdgpu_bo_free_kernel(&adev->gmc.stolen_vga_memory, NULL, &stolen_vga_buf);
+	amdgpu_bo_free_kernel(&adev->gmc.stolen_extended_memory, NULL,
+			      &stolen_extended_buf);
 }
 
 /**