[PATCHv2] drm: fb_helper: prefer to use mode, which is not DRM_MODE_TYPE_USERDEF

[Radek Dostal]

commit eaf99c749d43 ("drm: Perform cmdline mode parsing during connector
initialisation") breaks HDMI output on BeagleBone Black with LG TV
(model 19LS4R-ZA) when "video=HDMI-A-1:1280x720 at 60" is specified on
the command line.

The reason is newly added mode
'"1280x720" 60 74440 1280 1336 1472 1664 720 721 724 746 0x20 0x6'
, which is added by function drm_helper_probe_add_cmdline_mode (introduced
in above mentioned commit). This mode causes TV to go black and show "No
signal" message.

When cmdline_mode is set, it is preferred to use matching mode obtained
from EDID, than mode calculated by function
drm_mode_create_from_cmdline_mode

Signed-off-by: Radek Dostal <rd at radekdostal.com>
---
 v2: fixed if (prefer_non_userdef) condition, which was causing infinite
     loop before.

 drivers/gpu/drm/drm_fb_helper.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index cac4229..fac425e 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1284,6 +1284,7 @@ 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;
+	bool prefer_non_userdef;
 	bool prefer_non_interlace;
 
 	cmdline_mode = &fb_helper_conn->connector->cmdline_mode;
@@ -1296,6 +1297,7 @@ 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_userdef = true;
 	prefer_non_interlace = !cmdline_mode->interlace;
 again:
 	list_for_each_entry(mode, &fb_helper_conn->connector->modes, head) {
@@ -1312,6 +1314,9 @@ again:
 		if (cmdline_mode->interlace) {
 			if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
 				continue;
+		} else if (prefer_non_userdef) {
+			if (mode->type & DRM_MODE_TYPE_USERDEF)
+				continue;
 		} else if (prefer_non_interlace) {
 			if (mode->flags & DRM_MODE_FLAG_INTERLACE)
 				continue;
@@ -1319,6 +1324,11 @@ again:
 		return mode;
 	}
 
+	if (prefer_non_userdef) {
+		prefer_non_userdef = false;
+		goto again;
+	}
+
 	if (prefer_non_interlace) {
 		prefer_non_interlace = false;
 		goto again;
-- 
1.7.9.5