ecore drm2 - work around kms/drm bug seemingly when no flip event comes

so we request a flip so we can do vsync events. the flip event never
comes. i am not sure why it never comes, but we ask and nothing
arrives, and this basically halts all rendering in wayland compositor
mode as we are syncing rendering to vsync (of course). put in a
timeout of 0.05s (50ms) to try ask again if the event never comes and
log the error. this is a pretty useful workaround becauswe having your
entire display freeze is a ... bad thing.

@fix

src/lib/ecore_drm2/ecore_drm2_fb.c

@@ -263,6 +263,11 @@ ecore_drm2_fb_flip_complete(Ecore_Drm2_Output *output)
 
    EINA_SAFETY_ON_NULL_RETURN_VAL(output, EINA_FALSE);
 
+   if (output->flip_timeout)
+     {
+        ecore_timer_del(output->flip_timeout);
+        output->flip_timeout = NULL;
+     }
    if (output->current.fb && (output->current.fb != output->pending.fb))
      _ecore_drm2_fb_buffer_release(output, &output->current);
 
@@ -428,6 +433,21 @@ err:
    return EINA_FALSE;
 }
 
+static int _fb_atomic_flip(Ecore_Drm2_Output *output);
+static int _fb_flip(Ecore_Drm2_Output *output);
+
+static Eina_Bool
+_cb_flip_timeout(void *data)
+{
+   Ecore_Drm2_Output *output = data;
+
+   output->flip_timeout = NULL;
+   ERR("flip event callback timout 0.05sec - try again");
+   if (_ecore_drm2_use_atomic) _fb_atomic_flip(output);
+   else _fb_flip(output);
+   return EINA_FALSE;
+}
+
 static int
 _fb_atomic_flip(Ecore_Drm2_Output *output)
 {
@@ -453,6 +473,11 @@ _fb_atomic_flip(Ecore_Drm2_Output *output)
         ERR("Failed Atomic Commit: %m");
         return -1;
      }
+   else
+     {
+        if (output->flip_timeout) ecore_timer_del(output->flip_timeout);
+        output->flip_timeout = ecore_timer_add(0.05, _cb_flip_timeout, output);
+     }
 
    return 0;
 }
@@ -526,6 +551,11 @@ _fb_flip(Ecore_Drm2_Output *output)
                }
              usleep(100);
           }
+        else
+          {
+             if (output->flip_timeout) ecore_timer_del(output->flip_timeout);
+             output->flip_timeout = ecore_timer_add(0.05, _cb_flip_timeout, output);
+          }
      }
    while (repeat);
 

src/lib/ecore_drm2/ecore_drm2_outputs.c

@@ -916,6 +916,8 @@ _output_destroy(Ecore_Drm2_Device *dev EINA_UNUSED, Ecore_Drm2_Output *output)
    eina_stringshare_del(output->serial);
    eina_stringshare_del(output->relative.to);
 
+   if (output->flip_timeout) ecore_timer_del(output->flip_timeout);
+
    sym_drmModeFreeProperty(output->dpms);
    free(output->edid.blob);
 

src/lib/ecore_drm2/ecore_drm2_private.h

@@ -252,6 +252,8 @@ struct _Ecore_Drm2_Output
    /* unused when doing atomic */
    drmModePropertyPtr dpms;
 
+   Ecore_Timer *flip_timeout;
+
    Ecore_Drm2_Output_Mode *current_mode;
    Eina_List *modes;