From 564bfafb57ef45ab83f1e1acd6f309641bf17610 Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Wed, 21 Feb 2024 15:36:09 +0100
Subject: [PATCH] backends/drm: delay cursor updates with VRR by default for
 non-AMD GPUs

---
 src/backends/drm/drm_commit_thread.cpp | 15 +++++++++------
 src/backends/drm/drm_gpu.cpp           |  6 ++++++
 src/backends/drm/drm_gpu.h             |  2 ++
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/backends/drm/drm_commit_thread.cpp b/src/backends/drm/drm_commit_thread.cpp
index 0b8e8de7e6..4ecb1ba4b7 100644
--- a/src/backends/drm/drm_commit_thread.cpp
+++ b/src/backends/drm/drm_commit_thread.cpp
@@ -22,16 +22,19 @@ namespace KWin
  */
 static constexpr auto s_pageflipTimeout = 5s;
 
-// amdgpu doesn't handle this correctly, so it's off by default
-// https://gitlab.freedesktop.org/drm/amd/-/issues/2186
-static const bool s_delayVrrCursorUpdates = qEnvironmentVariableIntValue("KWIN_DRM_DELAY_VRR_CURSOR_UPDATES") == 1;
-
 DrmCommitThread::DrmCommitThread(DrmGpu *gpu, const QString &name)
 {
     if (!gpu->atomicModeSetting()) {
         return;
     }
-    m_thread.reset(QThread::create([this]() {
+
+    static bool delayVrrCursorUpdatesEnvSet = false;
+    static const bool delayVrrCursorUpdatesEnv = qEnvironmentVariableIntValue("KWIN_DRM_DELAY_VRR_CURSOR_UPDATES", &delayVrrCursorUpdatesEnvSet) == 1;
+    // amdgpu doesn't handle this correctly, so it's off by default for amd gpus
+    // See https://gitlab.freedesktop.org/drm/amd/-/issues/2186 for more details
+    const bool delayVrrCursorUpdates = (!delayVrrCursorUpdatesEnvSet && !gpu->isAmdgpu()) || delayVrrCursorUpdatesEnv;
+
+    m_thread.reset(QThread::create([this, delayVrrCursorUpdates]() {
         const auto thread = QThread::currentThread();
         gainRealTime();
         while (true) {
@@ -77,7 +80,7 @@ DrmCommitThread::DrmCommitThread(DrmGpu *gpu, const QString &name)
                 }
                 continue;
             }
-            if (m_commits.front()->isCursorOnly() && m_vrr && s_delayVrrCursorUpdates) {
+            if (m_commits.front()->isCursorOnly() && m_vrr && delayVrrCursorUpdates) {
                 // wait for a primary plane commit to be in, while still enforcing
                 // a minimum cursor refresh rate of 30Hz
                 const auto cursorTarget = m_lastPageflip + std::chrono::duration_cast<std::chrono::nanoseconds>(1s) / 30;
diff --git a/src/backends/drm/drm_gpu.cpp b/src/backends/drm/drm_gpu.cpp
index 62afaf9191..aee08ab737 100644
--- a/src/backends/drm/drm_gpu.cpp
+++ b/src/backends/drm/drm_gpu.cpp
@@ -80,6 +80,7 @@ DrmGpu::DrmGpu(DrmBackend *backend, const QString &devNode, int fd, dev_t device
     DrmUniquePtr<drmVersion> version(drmGetVersion(fd));
     m_isI915 = strstr(version->name, "i915");
     m_isNVidia = strstr(version->name, "nvidia-drm");
+    m_isAmdgpu = strstr(version->name, "amdgpu");
     m_isVirtualMachine = strstr(version->name, "virtio") || strstr(version->name, "qxl")
         || strstr(version->name, "vmwgfx") || strstr(version->name, "vboxvideo");
 
@@ -700,6 +701,11 @@ bool DrmGpu::isNVidia() const
     return m_isNVidia;
 }
 
+bool DrmGpu::isAmdgpu() const
+{
+    return m_isAmdgpu;
+}
+
 bool DrmGpu::isRemoved() const
 {
     return m_isRemoved;
diff --git a/src/backends/drm/drm_gpu.h b/src/backends/drm/drm_gpu.h
index 656c435fa2..e387b17209 100644
--- a/src/backends/drm/drm_gpu.h
+++ b/src/backends/drm/drm_gpu.h
@@ -79,6 +79,7 @@ public:
     bool asyncPageflipSupported() const;
     bool isI915() const;
     bool isNVidia() const;
+    bool isAmdgpu() const;
     gbm_device *gbmDevice() const;
     EglDisplay *eglDisplay() const;
     DrmBackend *platform() const;
@@ -138,6 +139,7 @@ private:
     bool m_addFB2ModifiersSupported = false;
     bool m_isNVidia;
     bool m_isI915;
+    bool m_isAmdgpu;
     bool m_isVirtualMachine;
     bool m_supportsCursorPlaneHotspot = false;
     bool m_asyncPageflipSupported = false;