From f43e45c984382a7f02c4b9a8cf4c8c1019ad193b Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Mon, 17 Jul 2023 10:15:56 +0200
Subject: [PATCH] backends/drm: work around llvmpipe implicit sync not working

implicit sync doesn't work properly with glFlush + KMS and llvmpipe doesn't support
EGL_ANDROID_native_fence_sync either, so we need to wait for rendering to complete
in a blocking fashion.
---
 src/backends/drm/drm_egl_layer_surface.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/backends/drm/drm_egl_layer_surface.cpp b/src/backends/drm/drm_egl_layer_surface.cpp
index 97c3e97988..840ca6f8dc 100644
--- a/src/backends/drm/drm_egl_layer_surface.cpp
+++ b/src/backends/drm/drm_egl_layer_surface.cpp
@@ -143,6 +143,10 @@ bool EglGbmLayerSurface::endRendering(const QRegion &damagedRegion)
     m_surface.gbmSwapchain->release(m_surface.currentSlot);
     m_surface.timeQuery->end();
     glFlush();
+    if (m_eglBackend->contextObject()->isSoftwareRenderer()) {
+        // llvmpipe doesn't do synchronization properly: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9375
+        glFinish();
+    }
     const auto buffer = importBuffer(m_surface, m_surface.currentSlot.get());
     m_surface.renderEnd = std::chrono::steady_clock::now();
     if (buffer) {