drm/i915: Fail if we can't get a fence for gen2/3 tiled scanout

Gen2/3 display engine depends on the fence for tiled scanout. So if we
fail to get a fence fail the entire operation.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180221160235.11134-2-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -2123,6 +2123,8 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
 		goto err;
 
 	if (i915_vma_is_map_and_fenceable(vma)) {
+		int ret;
+
 		/* Install a fence for tiled scan-out. Pre-i965 always needs a
 		 * fence, whereas 965+ only requires a fence if using
 		 * framebuffer compression.  For simplicity, we always, when
@@ -2139,7 +2141,13 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
 		 * something and try to run the system in a "less than optimal"
 		 * mode that matches the user configuration.
 		 */
-		if (i915_vma_pin_fence(vma) == 0 && vma->fence)
+		ret = i915_vma_pin_fence(vma);
+		if (ret != 0 && INTEL_GEN(dev_priv) < 4) {
+			vma = ERR_PTR(ret);
+			goto err;
+		}
+
+		if (ret == 0 && vma->fence)
 			*out_flags |= PLANE_HAS_FENCE;
 	}