From 4b49ca7751748d2236fa8e0de347dd7f0d9a3b1c Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Mon, 25 Sep 2023 13:37:10 +0200
Subject: [PATCH] backends/drm: fix frame scheduling with pageflip timestamps
 in the future

---
 src/backends/drm/drm_commit_thread.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backends/drm/drm_commit_thread.cpp b/src/backends/drm/drm_commit_thread.cpp
index dc08c94ddd..30b66de916 100644
--- a/src/backends/drm/drm_commit_thread.cpp
+++ b/src/backends/drm/drm_commit_thread.cpp
@@ -226,7 +226,8 @@ bool DrmCommitThread::pageflipsPending()
 
 TimePoint DrmCommitThread::estimateNextVblank(TimePoint now) const
 {
-    const uint64_t pageflipsSince = (now - m_lastPageflip) / m_minVblankInterval;
+    // the pageflip timestamp may be in the future
+    const uint64_t pageflipsSince = now >= m_lastPageflip ? (now - m_lastPageflip) / m_minVblankInterval : 0;
     return m_lastPageflip + m_minVblankInterval * (pageflipsSince + 1);
 }
 }