[mutter/gnome-42] output/kms: Add more heuristics to decide when to offer fallback modes

[Jonas Ådahl <jadahl src gnome org>]

commit 877cc3eb7d44e2886395151f763ec09bea350444
Author: Mario Limonciello <mario limonciello amd com>
Date:   Thu Aug 18 13:36:20 2022 -0500

    output/kms: Add more heuristics to decide when to offer fallback modes
    
    If the panel is connected via eDP and supports more than one mode
    at different resolutions don't try to add more.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2586>
    (cherry picked from commit 96aa0fb8536eca579ceb1b17d83e19cf9e3e9e81)

 src/backends/native/meta-output-kms.c | 56 +++++++++++++++++++++++++++--------
 1 file changed, 44 insertions(+), 12 deletions(-)
---
diff --git a/src/backends/native/meta-output-kms.c b/src/backends/native/meta-output-kms.c
index f60d5ad0dd..91a4ccaed7 100644
--- a/src/backends/native/meta-output-kms.c
+++ b/src/backends/native/meta-output-kms.c
@@ -277,6 +277,45 @@ compare_modes (const void *one,
                     meta_crtc_mode_get_name (crtc_mode_two));
 }
 
+static gboolean
+are_all_modes_equally_sized (MetaOutputInfo *output_info)
+{
+  const MetaCrtcModeInfo *base =
+    meta_crtc_mode_get_info (output_info->modes[0]);
+  int i;
+
+  for (i = 1; i < output_info->n_modes; i++)
+    {
+      const MetaCrtcModeInfo *mode_info =
+        meta_crtc_mode_get_info (output_info->modes[i]);
+
+      if (base->width != mode_info->width ||
+          base->height != mode_info->height)
+        return FALSE;
+    }
+
+  return TRUE;
+}
+
+static void
+maybe_add_fallback_modes (const MetaKmsConnectorState *connector_state,
+                          MetaOutputInfo              *output_info,
+                          MetaGpuKms                  *gpu_kms,
+                          MetaKmsConnector            *kms_connector)
+{
+  if (!connector_state->has_scaling)
+    return;
+
+  if (output_info->connector_type == DRM_MODE_CONNECTOR_eDP &&
+      !are_all_modes_equally_sized (output_info))
+    return;
+
+  meta_topic (META_DEBUG_KMS, "Adding common modes to connector %u on %s",
+              meta_kms_connector_get_id (kms_connector),
+              meta_gpu_kms_get_file_path (gpu_kms));
+  add_common_modes (output_info, gpu_kms);
+}
+
 static gboolean
 init_output_modes (MetaOutputInfo    *output_info,
                    MetaGpuKms        *gpu_kms,
@@ -305,14 +344,7 @@ init_output_modes (MetaOutputInfo    *output_info,
         output_info->preferred_mode = output_info->modes[i];
     }
 
-  if (connector_state->has_scaling)
-    {
-      meta_topic (META_DEBUG_KMS, "Adding common modes to connector %u on %s",
-                  meta_kms_connector_get_id (kms_connector),
-                  meta_gpu_kms_get_file_path (gpu_kms));
-      add_common_modes (output_info, gpu_kms);
-    }
-
+  maybe_add_fallback_modes (connector_state, output_info, gpu_kms, kms_connector);
   if (!output_info->modes)
     {
       g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
@@ -375,6 +407,10 @@ meta_output_kms_new (MetaGpuKms        *gpu_kms,
       output_info->height_mm = connector_state->height_mm;
     }
 
+  drm_connector_type = meta_kms_connector_get_connector_type (kms_connector);
+  output_info->connector_type =
+    meta_kms_connector_type_from_drm (drm_connector_type);
+
   if (!init_output_modes (output_info, gpu_kms, kms_connector, error))
     return NULL;
 
@@ -402,10 +438,6 @@ meta_output_kms_new (MetaGpuKms        *gpu_kms,
 
   meta_output_info_parse_edid (output_info, connector_state->edid_data);
 
-  drm_connector_type = meta_kms_connector_get_connector_type (kms_connector);
-  output_info->connector_type =
-    meta_kms_connector_type_from_drm (drm_connector_type);
-
   output_info->tile_info = connector_state->tile_info;
 
   output = g_object_new (META_TYPE_OUTPUT_KMS,