From 9f030ecd40c4d519d3cc6f349c27c17b4ff5d5fd Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Wed, 28 Apr 2021 23:18:28 +0300
Subject: [PATCH] platforms/drm: Enable atomic modesetting in hot plugged gpus

At the moment, if a gpu is hot plugged, it won't have atomic modesetting
enabled.
---
 src/plugins/platforms/drm/drm_backend.cpp | 6 ------
 src/plugins/platforms/drm/drm_gpu.cpp     | 6 ++++++
 src/plugins/platforms/drm/drm_gpu.h       | 3 +--
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/plugins/platforms/drm/drm_backend.cpp b/src/plugins/platforms/drm/drm_backend.cpp
index 321171365e..d3fde7fa8e 100644
--- a/src/plugins/platforms/drm/drm_backend.cpp
+++ b/src/plugins/platforms/drm/drm_backend.cpp
@@ -202,12 +202,6 @@ bool DrmBackend::initialize()
         addGpu(std::move(devices.at(gpu_index)));
     }
 
-    // trying to activate Atomic Mode Setting (this means also Universal Planes)
-    if (!qEnvironmentVariableIsSet("KWIN_DRM_NO_AMS")) {
-        for (auto gpu : m_gpus)
-            gpu->tryAMS();
-    }
-
     initCursor();
     if (!updateOutputs())
         return false;
diff --git a/src/plugins/platforms/drm/drm_gpu.cpp b/src/plugins/platforms/drm/drm_gpu.cpp
index a180ff194a..2f491d014d 100644
--- a/src/plugins/platforms/drm/drm_gpu.cpp
+++ b/src/plugins/platforms/drm/drm_gpu.cpp
@@ -76,6 +76,12 @@ DrmGpu::DrmGpu(DrmBackend *backend, QByteArray devNode, int fd, dev_t deviceId)
 
     m_socketNotifier = new QSocketNotifier(fd, QSocketNotifier::Read, this);
     connect(m_socketNotifier, &QSocketNotifier::activated, this, &DrmGpu::dispatchEvents);
+
+    // trying to activate Atomic Mode Setting (this means also Universal Planes)
+    static const bool atomicModesetting = !qEnvironmentVariableIsSet("KWIN_DRM_NO_AMS");
+    if (atomicModesetting) {
+        tryAMS();
+    }
 }
 
 DrmGpu::~DrmGpu()
diff --git a/src/plugins/platforms/drm/drm_gpu.h b/src/plugins/platforms/drm/drm_gpu.h
index 5c9efa5e9e..0dfabdbff5 100644
--- a/src/plugins/platforms/drm/drm_gpu.h
+++ b/src/plugins/platforms/drm/drm_gpu.h
@@ -105,9 +105,7 @@ Q_SIGNALS:
     void outputDisabled(DrmOutput *output);
 
 protected:
-
     friend class DrmBackend;
-    void tryAMS();
     bool updateOutputs();
 
 private:
@@ -115,6 +113,7 @@ private:
     DrmPlane *getCompatiblePlane(DrmPlane::TypeIndex typeIndex, DrmCrtc *crtc);
     DrmOutput *findOutput(quint32 connector);
     void removeOutput(DrmOutput *output);
+    void tryAMS();
 
     DrmBackend* const m_backend;
     AbstractEglBackend *m_eglBackend;