drm: Use preferred mode for outputs instead of current mode

When enumerating outputs pick the preferred mode instead of the current
active mode, which may be e.g. a very low res mode.

Sofar we've been relying on fbcon setting up the modes for us, but as
mentioned in https://bugs.freedesktop.org/show_bug.cgi?id=101520#c22
we really should not rely on this.

With the recent flickerfree boot changes we can no longer rely on fbcon
to do the setup for us, hence this commit. For now this commit only
changes the mode-picking logic on UEFI setups as we only have
flickerfree boot there. Once the setup code is more mature we should
probably always use it.

Closes #68

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 54 insertions, 2 deletions

diff --git a/src/plugins/renderers/drm/plugin.c b/src/plugins/renderers/drm/plugin.c
index ac2f1ad5..1ff2b295 100644
--- a/src/plugins/renderers/drm/plugin.c
+++ b/src/plugins/renderers/drm/plugin.c
@@ -137,6 +137,7 @@ struct _ply_renderer_backend
 
         uint32_t                         is_active : 1;
         uint32_t        requires_explicit_flushing : 1;
+        uint32_t                use_preferred_mode : 1;
 };
 
 ply_renderer_plugin_interface_t *ply_renderer_backend_get_interface (void);
@@ -149,6 +150,36 @@ static bool reset_scan_out_buffer_if_needed (ply_renderer_backend_t *backend,
 static void flush_head (ply_renderer_backend_t *backend,
                         ply_renderer_head_t    *head);
 
+static bool efi_enabled (void)
+{
+        return ply_directory_exists ("/sys/firmware/efi/efivars");
+}
+
+/* A small helper to determine if we should try to keep the current mode
+ * or pick the best mode ourselves, we keep the current mode if:
+ * 1. The user specified a specific mode using video= on the commandline
+ * 2. The code to pick the best mode was added because with flicker-free boot
+ *    we can no longer rely on the kernel's fbcon code setting things up.
+ *    We should be able to do a better job then fbcon regardless, but for
+ *    now lets only use the new code on flicker-free systems until it is
+ *    more mature, this means only using it on UEFI systems.
+ */
+static bool
+should_use_preferred_mode (void)
+{
+        bool use_preferred_mode = true;
+
+        if (ply_kernel_command_line_get_string_after_prefix ("video="))
+                use_preferred_mode = false;
+
+        if (!efi_enabled ())
+                use_preferred_mode = false;
+
+        ply_trace ("should_use_preferred_mode: %d", use_preferred_mode);
+
+        return use_preferred_mode;
+}
+
 static bool
 ply_renderer_buffer_map (ply_renderer_backend_t *backend,
                          ply_renderer_buffer_t  *buffer)
@@ -776,6 +807,7 @@ create_backend (const char     *device_name,
         backend->requires_explicit_flushing = true;
         backend->output_buffers = ply_hashtable_new (ply_hashtable_direct_hash,
                                                      ply_hashtable_direct_compare);
+        backend->use_preferred_mode = should_use_preferred_mode ();
 
         return backend;
 }
@@ -1025,6 +1057,22 @@ find_index_of_mode (ply_renderer_backend_t *backend,
 }
 
 static int
+get_index_of_preferred_mode (drmModeConnector *connector)
+{
+        int i;
+
+        for (i = 0; i < connector->count_modes; i++)
+                if (connector->modes[i].type & DRM_MODE_TYPE_PREFERRED) {
+                        ply_trace ("Found preferred mode %dx%d at index %d\n",
+                                   connector->modes[i].hdisplay,
+                                   connector->modes[i].vdisplay, i);
+                        return i;
+                }
+
+        return -1;
+}
+
+static int
 get_index_of_active_mode (ply_renderer_backend_t *backend,
                           drmModeCrtc            *controller,
                           drmModeConnector       *connector)
@@ -1056,7 +1104,7 @@ create_heads_for_active_connectors (ply_renderer_backend_t *backend)
                 drmModeCrtc *controller;
                 uint32_t controller_id;
                 uint32_t console_buffer_id;
-                int connector_mode_index;
+                int connector_mode_index = -1;
                 int gamma_size;
                 ply_pixel_buffer_rotation_t rotation;
                 bool tiled;
@@ -1097,7 +1145,11 @@ create_heads_for_active_connectors (ply_renderer_backend_t *backend)
 
                 ply_renderer_connector_get_rotation_and_tiled (backend, connector, &rotation, &tiled);
 
-                connector_mode_index = get_index_of_active_mode (backend, controller, connector);
+                if (!tiled && backend->use_preferred_mode)
+                        connector_mode_index = get_index_of_preferred_mode (connector);
+
+                if (connector_mode_index < 0)
+                        connector_mode_index = get_index_of_active_mode (backend, controller, connector);
 
                 /* If we couldn't find the current active mode, fall back to the first available.
                  */