From 0d67a0b48a500b615ff4af7456b1461a38090e48 Mon Sep 17 00:00:00 2001
From: Roman Gilg <subdiff@gmail.com>
Date: Mon, 21 Oct 2019 14:56:33 +0200
Subject: [PATCH] Fix non-atomic output init

Summary:
The initial blank needs to happen after the output device has been
initialized to get the current mode size.

Also we can't assert in legacy mode on the page flip pending since
a page flip can also be the result of a CRTC blank using a different.

BUG: 412684
FIXED-IN: 5.17.1

Test Plan: Full Plasma session

Reviewers: #kwin, zzag

Reviewed By: #kwin, zzag

Subscribers: zzag, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D24829
---
 plugins/platforms/drm/drm_output.cpp | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/plugins/platforms/drm/drm_output.cpp b/plugins/platforms/drm/drm_output.cpp
index a74371ba5b..b1655a12f7 100644
--- a/plugins/platforms/drm/drm_output.cpp
+++ b/plugins/platforms/drm/drm_output.cpp
@@ -252,8 +252,6 @@ bool DrmOutput::init(drmModeConnector *connector)
         if (!initPrimaryPlane()) {
             return false;
         }
-    } else if (!m_crtc->blank()) {
-        return false;
     }
 
     setInternal(connector->connector_type == DRM_MODE_CONNECTOR_LVDS || connector->connector_type == DRM_MODE_CONNECTOR_eDP);
@@ -268,6 +266,12 @@ bool DrmOutput::init(drmModeConnector *connector)
     }
 
     initOutputDevice(connector);
+
+    if (!m_backend->atomicModeSetting() && !m_crtc->blank()) {
+        // We use legacy mode and the initial output blank failed.
+        return false;
+    }
+
     updateDpms(KWayland::Server::OutputInterface::DpmsMode::On);
     return true;
 }
@@ -745,8 +749,10 @@ void DrmOutput::setWaylandMode()
 
 void DrmOutput::pageFlipped()
 {
-    Q_ASSERT(m_pageFlipPending);
+    // In legacy mode we might get a page flip through a blank.
+    Q_ASSERT(m_pageFlipPending || !m_backend->atomicModeSetting());
     m_pageFlipPending = false;
+
     if (m_deleted) {
         deleteLater();
         return;