From ab6d986e8ced85d68f1a38f80142cd3fe35c080f Mon Sep 17 00:00:00 2001
From: Conn O'Griofa <connogriofa@gmail.com>
Date: Fri, 6 Sep 2019 08:44:46 -0700
Subject: [PATCH] KMSDRM_GLES_SwapWindow: fix non-vsync case If
 KMSDRM_drmModeSetCrtc is called when the swap interval is set to 0, the
 driver behaves as though vertical sync is engaged by limiting framerate to
 the refresh rate, but performance is much worse than with vertical sync
 enabled.

Resolve this issue by ensuring that the Crtc is only set up once,
and KMSDRM_drmModePageFlip is called, albeit without any followup
queueing or waiting for flips.
---
 src/video/kmsdrm/SDL_kmsdrmopengles.c | 38 +++++++++++----------------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/src/video/kmsdrm/SDL_kmsdrmopengles.c b/src/video/kmsdrm/SDL_kmsdrmopengles.c
index 9616c832f..212c2b5d7 100644
--- a/src/video/kmsdrm/SDL_kmsdrmopengles.c
+++ b/src/video/kmsdrm/SDL_kmsdrmopengles.c
@@ -140,32 +140,24 @@ KMSDRM_GLES_SwapWindow(_THIS, SDL_Window * window) {
     if (fb_info == NULL) {
         return 0;
     }
-    if (_this->egl_data->egl_swapinterval == 0) {
-        /* Swap buffers instantly, possible tearing */
-        /* SDL_LogDebug(SDL_LOG_CATEGORY_VIDEO, "drmModeSetCrtc(%d, %u, %u, 0, 0, &%u, 1, &%ux%u@%u)",
-            vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id, vdata->saved_conn_id,
-            displaydata->cur_mode.hdisplay, displaydata->cur_mode.vdisplay, displaydata->cur_mode.vrefresh); */
-        ret = KMSDRM_drmModeSetCrtc(vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id,
-                                    0, 0, &vdata->saved_conn_id, 1, &displaydata->cur_mode);
-        if(ret != 0) {
-            SDL_LogError(SDL_LOG_CATEGORY_VIDEO, "Could not pageflip with drmModeSetCrtc: %d", ret);
+
+    /* Have we already setup the CRTC to one of the GBM buffers? Do so if we have not,
+       or FlipPage won't work in some cases. */
+    if (!wdata->crtc_ready) {
+        if(!KMSDRM_GLES_SetupCrtc(_this, window)) {
+            SDL_LogError(SDL_LOG_CATEGORY_VIDEO, "Could not set up CRTC for doing pageflips");
+            return 0;
         }
-    } else {
+    }
+
+    /* SDL_LogDebug(SDL_LOG_CATEGORY_VIDEO, "drmModePageFlip(%d, %u, %u, DRM_MODE_PAGE_FLIP_EVENT, &wdata->waiting_for_flip)",
+        vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id); */
+    ret = KMSDRM_drmModePageFlip(vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id,
+                                 DRM_MODE_PAGE_FLIP_EVENT, &wdata->waiting_for_flip);
+
+    if (_this->egl_data->egl_swapinterval == 1) {
         /* Queue page flip at vsync */
 
-        /* Have we already setup the CRTC to one of the GBM buffers? Do so if we have not,
-           or FlipPage won't work in some cases. */
-        if (!wdata->crtc_ready) {
-            if(!KMSDRM_GLES_SetupCrtc(_this, window)) {
-                SDL_LogError(SDL_LOG_CATEGORY_VIDEO, "Could not set up CRTC for doing vsync-ed pageflips");
-                return 0;
-            }
-        }
-
-        /* SDL_LogDebug(SDL_LOG_CATEGORY_VIDEO, "drmModePageFlip(%d, %u, %u, DRM_MODE_PAGE_FLIP_EVENT, &wdata->waiting_for_flip)",
-            vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id); */
-        ret = KMSDRM_drmModePageFlip(vdata->drm_fd, displaydata->crtc_id, fb_info->fb_id,
-                                     DRM_MODE_PAGE_FLIP_EVENT, &wdata->waiting_for_flip);
         if (ret == 0) {
             wdata->waiting_for_flip = SDL_TRUE;
         } else {