drm/i915: handle shared framebuffers when flipping

index 8359c50..cf5a91d 100644
@@ -4863,7 +4863,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	struct drm_gem_object *obj;
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 	struct intel_unpin_work *work;
-	unsigned long flags;
+	unsigned long flags, offset;
 	int pipesrc_reg = (intel_crtc->pipe == 0) ? PIPEASRC : PIPEBSRC;
 	int ret, pipesrc;
 	u32 flip_mask;

@@ -4925,19 +4925,23 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 		while (I915_READ(ISR) & flip_mask)
 			;
 
+	/* Offset into the new buffer for cases of shared fbs between CRTCs */
+	offset = obj_priv->gtt_offset;
+	offset += (crtc->y * fb->pitch) + (crtc->x * (fb->bits_per_pixel) / 8);
+
 	BEGIN_LP_RING(4);
 	if (IS_I965G(dev)) {
 		OUT_RING(MI_DISPLAY_FLIP |
 			 MI_DISPLAY_FLIP_PLANE(intel_crtc->plane));
 		OUT_RING(fb->pitch);
-		OUT_RING(obj_priv->gtt_offset | obj_priv->tiling_mode);
+		OUT_RING(offset | obj_priv->tiling_mode);
 		pipesrc = I915_READ(pipesrc_reg); 
 		OUT_RING(pipesrc & 0x0fff0fff);
 	} else {
 		OUT_RING(MI_DISPLAY_FLIP_I915 |
 			 MI_DISPLAY_FLIP_PLANE(intel_crtc->plane));
 		OUT_RING(fb->pitch);
-		OUT_RING(obj_priv->gtt_offset);
+		OUT_RING(offset);
 		OUT_RING(MI_NOOP);
 	}
 	ADVANCE_LP_RING();