Implement max swapchain images setting, implement it first for DRM/KMS context

config.def.h

@@ -411,6 +411,8 @@ static const bool disable_composition = false;
 /* Video VSYNC (recommended) */
 static const bool vsync = true;
 
+static const unsigned max_swapchain_images = 3;
+
 /* Attempts to hard-synchronize CPU and GPU.
  * Can reduce latency at cost of performance. */
 static const bool hard_sync = false;

configuration.c

@@ -495,6 +495,7 @@ static void config_set_defaults(void)
    settings->video.fullscreen_y          = fullscreen_y;
    settings->video.disable_composition   = disable_composition;
    settings->video.vsync                 = vsync;
+   settings->video.max_swapchain_images  = max_swapchain_images;
    settings->video.hard_sync             = hard_sync;
    settings->video.hard_sync_frames      = hard_sync_frames;
    settings->video.frame_delay           = frame_delay;
@@ -1291,6 +1292,7 @@ static bool config_load_file(const char *path, bool set_defaults)
    CONFIG_GET_INT_BASE (conf, settings, video.monitor_index, "video_monitor_index");
    CONFIG_GET_BOOL_BASE(conf, settings, video.disable_composition, "video_disable_composition");
    CONFIG_GET_BOOL_BASE(conf, settings, video.vsync, "video_vsync");
+   CONFIG_GET_INT_BASE(conf, settings, video.max_swapchain_images, "video_max_swapchain_images");
    CONFIG_GET_BOOL_BASE(conf, settings, video.hard_sync, "video_hard_sync");
 
 #ifdef HAVE_MENU
@@ -2658,6 +2660,8 @@ bool config_save_file(const char *path)
 
 
    config_set_bool(conf,  "video_vsync", settings->video.vsync);
+   config_set_int(conf,   "video_max_swapchain_images",
+         settings->video.max_swapchain_images);
    config_set_bool(conf,  "video_hard_sync", settings->video.hard_sync);
    config_set_int(conf,   "video_hard_sync_frames",
          settings->video.hard_sync_frames);

configuration.h

@@ -55,6 +55,7 @@ typedef struct settings
       bool vsync;
       bool hard_sync;
       bool black_frame_insertion;
+      unsigned max_swapchain_images;
       unsigned swap_interval;
       unsigned hard_sync_frames;
       unsigned frame_delay;

gfx/drivers_context/drm_ctx.c

@@ -245,6 +245,7 @@ static bool gfx_ctx_drm_queue_flip(void)
 static void gfx_ctx_drm_swap_buffers(void *data)
 {
    gfx_ctx_drm_data_t *drm = (gfx_ctx_drm_data_t*)data;
+   settings_t    *settings = config_get_ptr();
 
    switch (drm_api)
    {
@@ -269,12 +270,11 @@ static void gfx_ctx_drm_swap_buffers(void *data)
 
    waiting_for_flip = gfx_ctx_drm_queue_flip();
 
-   if (gbm_surface_has_free_buffers(g_gbm_surface))
+   /* Triple-buffered page flips */
+   if (settings->video.max_swapchain_images >= 3 &&
+         gbm_surface_has_free_buffers(g_gbm_surface))
       return;
 
-   /* We have to wait for this flip to finish. 
-    * This shouldn't happen as we have triple buffered page-flips. */
-   RARCH_WARN("[KMS]: Triple buffering is not working correctly ...\n");
    gfx_ctx_drm_wait_flip(true);  
 }
 

intl/msg_hash_us.c

@@ -1105,6 +1105,8 @@ static const char *menu_hash_to_str_us_label_enum(enum msg_hash_enums msg)
 {
    switch (msg)
    {
+      case MENU_ENUM_LABEL_VIDEO_MAX_SWAPCHAIN_IMAGES:
+         return "video_max_swapchain_images";
       case MENU_ENUM_LABEL_CORE_SETTINGS:
          return "core_settings";
       case MENU_ENUM_LABEL_CB_MENU_WALLPAPER:
@@ -1997,6 +1999,8 @@ const char *msg_hash_to_str_us(enum msg_hash_enums msg)
          return "Compiled against API";
       case MSG_FAILED_TO_LOAD:
          return "Failed to load";
+      case MENU_ENUM_LABEL_VALUE_VIDEO_MAX_SWAPCHAIN_IMAGES:
+         return "Max swapchain images";
       case MSG_ERROR_LIBRETRO_CORE_REQUIRES_CONTENT:
          return "Libretro core requires content, but nothing was provided.";
       case MSG_CONTENT_LOADING_SKIPPED_IMPLEMENTATION_WILL_DO_IT:

menu/menu_displaylist.c

@@ -4068,6 +4068,9 @@ bool menu_displaylist_ctl(enum menu_displaylist_ctl_state type, void *data)
          menu_displaylist_parse_settings_enum(menu, info,
                MENU_ENUM_LABEL_VIDEO_VSYNC,
                PARSE_ONLY_BOOL, false);
+         menu_displaylist_parse_settings_enum(menu, info,
+               MENU_ENUM_LABEL_VIDEO_MAX_SWAPCHAIN_IMAGES,
+               PARSE_ONLY_UINT, false);
          menu_displaylist_parse_settings_enum(menu, info,
                MENU_ENUM_LABEL_VIDEO_SWAP_INTERVAL,
                PARSE_ONLY_UINT, false);

menu/menu_setting.c

@@ -5247,6 +5247,21 @@ static bool setting_append_list(
                );
          menu_settings_list_current_add_enum_idx(list, list_info, MENU_ENUM_LABEL_VIDEO_VSYNC);
 
+         CONFIG_UINT(
+               list, list_info,
+               &settings->video.max_swapchain_images,
+               msg_hash_to_str(MENU_ENUM_LABEL_VIDEO_MAX_SWAPCHAIN_IMAGES),
+               msg_hash_to_str(MENU_ENUM_LABEL_VALUE_VIDEO_MAX_SWAPCHAIN_IMAGES),
+               max_swapchain_images,
+               &group_info,
+               &subgroup_info,
+               parent_group,
+               general_write_handler,
+               general_read_handler);
+         menu_settings_list_current_add_range(list, list_info, 1, 4, 1, true, true);
+         settings_data_list_current_add_flags(list, list_info, SD_FLAG_CMD_APPLY_AUTO|SD_FLAG_ADVANCED);
+         menu_settings_list_current_add_enum_idx(list, list_info, MENU_ENUM_LABEL_VIDEO_MAX_SWAPCHAIN_IMAGES);
+
          CONFIG_UINT(
                list, list_info,
                &settings->video.swap_interval,

msg_hash.h

@@ -323,6 +323,7 @@ enum msg_hash_enums
    MENU_ENUM_LABEL_VIDEO_FILTER_FLICKER,
    MENU_ENUM_LABEL_VIDEO_SOFT_FILTER,
    MENU_ENUM_LABEL_VIDEO_SWAP_INTERVAL,
+   MENU_ENUM_LABEL_VIDEO_MAX_SWAPCHAIN_IMAGES,
    MENU_ENUM_LABEL_VIDEO_GPU_SCREENSHOT,
    MENU_ENUM_LABEL_VIDEO_FULLSCREEN,
    MENU_ENUM_LABEL_VIDEO_BLACK_FRAME_INSERTION,
@@ -367,6 +368,7 @@ enum msg_hash_enums
    MENU_ENUM_LABEL_VALUE_VIDEO_VSYNC,
    MENU_ENUM_LABEL_VALUE_VIDEO_HARD_SYNC,
    MENU_ENUM_LABEL_VALUE_VIDEO_SWAP_INTERVAL,
+   MENU_ENUM_LABEL_VALUE_VIDEO_MAX_SWAPCHAIN_IMAGES,
    MENU_ENUM_LABEL_VALUE_VIDEO_GPU_SCREENSHOT,
    MENU_ENUM_LABEL_VALUE_VIDEO_FULLSCREEN,
    MENU_ENUM_LABEL_VALUE_VIDEO_FORCE_ASPECT,

retroarch.cfg

@@ -141,6 +141,9 @@
 # Video vsync.
 # video_vsync = true
 
+# Video swapchain images.
+# video_max_swapchain_images = 3
+
 # Forcibly disable sRGB FBO support. Some Intel OpenGL drivers on Windows
 # have video problems with sRGB FBO support enabled.
 # video_force_srgb_disable = false