drm: Prefer noninterlace cmdline mode unless explicitly specified

Currently drm_pick_cmdline_mode() doesn't care about the interlace
when the given mode line has no "i" suffix.  That is, when there are
multiple entries for the same resolution, an interlace mode might be
picked up just depending on the assigned order, and there is no way to
exclude it.

This patch changes the logic for the mode selection, to prefer the
noninterlace mode unless the interlace mode is explicitly given.
When no matching mode is found, it still tries the interlace mode as
fallback.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_fb_helper.c

@@ -1159,6 +1159,7 @@ struct drm_display_mode *drm_pick_cmdline_mode(struct drm_fb_helper_connector *f
 {
 	struct drm_cmdline_mode *cmdline_mode;
 	struct drm_display_mode *mode = NULL;
+	bool prefer_non_interlace;
 
 	cmdline_mode = &fb_helper_conn->cmdline_mode;
 	if (cmdline_mode->specified == false)
@@ -1170,6 +1171,8 @@ struct drm_display_mode *drm_pick_cmdline_mode(struct drm_fb_helper_connector *f
 	if (cmdline_mode->rb || cmdline_mode->margins)
 		goto create_mode;
 
+	prefer_non_interlace = !cmdline_mode->interlace;
+ again:
 	list_for_each_entry(mode, &fb_helper_conn->connector->modes, head) {
 		/* check width/height */
 		if (mode->hdisplay != cmdline_mode->xres ||
@@ -1184,10 +1187,18 @@ struct drm_display_mode *drm_pick_cmdline_mode(struct drm_fb_helper_connector *f
 		if (cmdline_mode->interlace) {
 			if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
 				continue;
+		} else if (prefer_non_interlace) {
+			if (mode->flags & DRM_MODE_FLAG_INTERLACE)
+				continue;
 		}
 		return mode;
 	}
 
+	if (prefer_non_interlace) {
+		prefer_non_interlace = false;
+		goto again;
+	}
+
 create_mode:
 	mode = drm_mode_create_from_cmdline_mode(fb_helper_conn->connector->dev,
 						 cmdline_mode);