drm/i915: Set preferred mode for integrated TV according to TV format

In order to get best possible quality image we chose 640x480 for
NTSC, PAL and 480p, 1280x720 for 720p, 1920x1080 for 1080i/p
TV format respectively.
Signed-off-by: Ma Ling <ling.ma@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_tv.c

@@ -1490,6 +1490,27 @@ static struct input_res {
 	{"1920x1080", 1920, 1080},
 };
 
+/*
+ * Chose preferred mode  according to line number of TV format
+ */
+static void
+intel_tv_chose_preferred_modes(struct drm_connector *connector,
+			       struct drm_display_mode *mode_ptr)
+{
+	struct intel_output *intel_output = to_intel_output(connector);
+	const struct tv_mode *tv_mode = intel_tv_mode_find(intel_output);
+
+	if (tv_mode->nbr_end < 480 && mode_ptr->vdisplay == 480)
+		mode_ptr->type |= DRM_MODE_TYPE_PREFERRED;
+	else if (tv_mode->nbr_end > 480) {
+		if (tv_mode->progressive == true && tv_mode->nbr_end < 720) {
+			if (mode_ptr->vdisplay == 720)
+				mode_ptr->type |= DRM_MODE_TYPE_PREFERRED;
+		} else if (mode_ptr->vdisplay == 1080)
+				mode_ptr->type |= DRM_MODE_TYPE_PREFERRED;
+	}
+}
+
 /**
  * Stub get_modes function.
  *
@@ -1544,6 +1565,7 @@ intel_tv_get_modes(struct drm_connector *connector)
 		mode_ptr->clock = (int) tmp;
 
 		mode_ptr->type = DRM_MODE_TYPE_DRIVER;
+		intel_tv_chose_preferred_modes(connector, mode_ptr);
 		drm_mode_probed_add(connector, mode_ptr);
 		count++;
 	}