From 83d797785b0a253319e4ce9a9fbe0ff55e940a20 Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Thu, 24 Feb 2022 05:39:07 +0100
Subject: [PATCH] backends/drm: wait for pending pageflips before doing a
 modeset

If we don't, KWin may get a pageflip event for an output that is already
considered as being turned off
---
 src/backends/drm/drm_gpu.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/backends/drm/drm_gpu.cpp b/src/backends/drm/drm_gpu.cpp
index e08ba399bc..e316334a0b 100644
--- a/src/backends/drm/drm_gpu.cpp
+++ b/src/backends/drm/drm_gpu.cpp
@@ -733,6 +733,8 @@ bool DrmGpu::maybeModeset()
         // commit only once all pipelines are ready for presentation
         return true;
     }
+    // make sure there's no pending pageflips
+    waitIdle();
     const bool ok = DrmPipeline::commitPipelines(pipelines, DrmPipeline::CommitMode::CommitModeset, unusedObjects());
     for (DrmPipeline *pipeline : qAsConst(pipelines)) {
         if (pipeline->modesetPresentPending()) {