drm/i915: Use the first mode if there is no preferred mode in the EDID

This matches the algorithm used by earlier kernels when selecting the
mode for the fbcon. And only if there is no modes at all, do we fall
back to using the BIOS configuration. Seamless transition is still
preserved (from the BIOS configuration to ours) so long as the BIOS has
also chosen what we hope is the native configuration.

Change-Id: If11bc97f1d4c29e2828c152a0c40c7579051046b
Reported-by: Knut Petersen <Knut_Petersen@t-online.de>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78655
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Knut Petersen <Knut_Petersen@t-online.de>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[Jani: applied Chris' "Please imagine that I wrote this correctly."]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Bug-Tizen: TC-354
Signed-off-by: Jin Song <jin.kyu.song@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
index ff9a509..d2f6c92 100644 (file)
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -289,6 +289,7 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
                struct drm_connector *connector;
                struct drm_encoder *encoder;
                struct drm_fb_helper_crtc *new_crtc;
+               struct drm_display_mode *current_mode;
 
                fb_conn = fb_helper->connector_info[i];
                connector = fb_conn->connector;
@@ -334,20 +335,36 @@ static bool intel_fb_initial_config(struct drm_fb_helper *fb_helper,
                                                           height);
                        intel_mode_from_pipe_config(&encoder->crtc->hwmode,
                                                    &to_intel_crtc(encoder->crtc)->config);
-                       modes[i] = &encoder->crtc->hwmode;
+                       current_mode = &encoder->crtc->hwmode;
 
                        if (preferred &&
-                           !drm_mode_same_size(preferred, modes[i])) {
+                           !drm_mode_same_size(preferred, current_mode)) {
                                DRM_DEBUG_KMS("using preferred mode %s "
                                              "instead of current mode %s "
                                              "on connector %d\n",
                                              preferred->name,
-                                             modes[i]->name,
+                                             current_mode->name,
                                              fb_conn->connector->base.id);
                                modes[i] = preferred;
                        }
                }
 
+               /* No preferred mode marked by the EDID? Are there any modes? */
+               if (!modes[i] && !list_empty(&connector->modes)) {
+                       DRM_DEBUG_KMS("using first mode listed on connector %s\n",
+                                     drm_get_connector_name(connector));
+                       modes[i] = list_first_entry(&connector->modes,
+                                                   struct drm_display_mode,
+                                                   head);
+               }
+
+               /* last resort: use current mode */
+               if (!modes[i]) {
+                       DRM_DEBUG_KMS("looking for current mode on connector %s\n",
+                                       drm_get_connector_name(connector));
+                       modes[i] = current_mode;
+               }
+
                crtcs[i] = new_crtc;
 
                DRM_DEBUG_KMS("connector %s on crtc %d: %s\n",