drm/vmwgfx: Fixed topology boundary checking for Screen Targets

For a Screen Target capable display device, the display topology is
limited by SVGA_REG_MAX_PRIMARY_BOUNDING_BOX_MEM.  Two values are
checked against this limit:
  1.  Size of the bounding box enclosing all the displays, and
  2.  Size of the total number of displays, e.g. framebuffers

The limitations above mean we do not have exact max width and
height for the topology.  The best current option is to set those to
the maximum texture width/height.
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -1077,9 +1077,8 @@ int vmw_kms_init(struct vmw_private *dev_priv)
 	dev->mode_config.funcs = &vmw_kms_funcs;
 	dev->mode_config.min_width = 1;
 	dev->mode_config.min_height = 1;
-	/* assumed largest fb size */
-	dev->mode_config.max_width = 8192;
-	dev->mode_config.max_height = 8192;
+	dev->mode_config.max_width = dev_priv->texture_max_width;
+	dev->mode_config.max_height = dev_priv->texture_max_height;
 
 	ret = vmw_kms_stdu_init_display(dev_priv);
 	if (ret) {
@@ -1580,6 +1579,7 @@ int vmw_kms_update_layout_ioctl(struct drm_device *dev, void *data,
 	unsigned rects_size;
 	int ret;
 	int i;
+	u64 total_pixels = 0;
 	struct drm_mode_config *mode_config = &dev->mode_config;
 	struct drm_vmw_rect bounding_box = {0};
 
@@ -1622,20 +1622,31 @@ int vmw_kms_update_layout_ioctl(struct drm_device *dev, void *data,
 
 		if (rects[i].y + rects[i].h > bounding_box.h)
 			bounding_box.h = rects[i].y + rects[i].h;
+
+		total_pixels += (u64) rects[i].w * (u64) rects[i].h;
 	}
 
-	/*
-	 * For Screen Target Display Unit, all the displays must fit
-	 * inside of maximum texture size.
-	 */
-	if (dev_priv->active_display_unit == vmw_du_screen_target)
-		if (bounding_box.w > dev_priv->texture_max_width ||
-		    bounding_box.h > dev_priv->texture_max_height) {
-			DRM_ERROR("Layout exceeds maximum texture size\n");
+	if (dev_priv->active_display_unit == vmw_du_screen_target) {
+		/*
+		 * For Screen Targets, the limits for a toplogy are:
+		 *	1. Bounding box (assuming 32bpp) must be < prim_bb_mem
+		 *      2. Total pixels (assuming 32bpp) must be < prim_bb_mem
+		 */
+		u64 bb_mem    = bounding_box.w * bounding_box.h * 4;
+		u64 pixel_mem = total_pixels * 4;
+
+		if (bb_mem > dev_priv->prim_bb_mem) {
+			DRM_ERROR("Topology is beyond supported limits.\n");
 			ret = -EINVAL;
 			goto out_free;
 		}
 
+		if (pixel_mem > dev_priv->prim_bb_mem) {
+			DRM_ERROR("Combined output size too large\n");
+			ret = -EINVAL;
+			goto out_free;
+		}
+	}
 
 	vmw_du_update_layout(dev_priv, arg->num_outputs, rects);