backends/drm: force a modeset when connectors are unplugged

And turn off unused CRTCs with legacy

BUG: 478476

src/backends/drm/drm_gpu.cpp

@@ -578,6 +578,8 @@ void DrmGpu::removeOutput(DrmOutput *output)
     m_drmOutputs.removeOne(output);
     Q_EMIT outputRemoved(output);
     output->unref();
+    // force a modeset to make sure unused objects are cleaned up
+    m_forceModeset = true;
 }
 
 DrmBackend *DrmGpu::platform() const
@@ -740,9 +742,9 @@ bool DrmGpu::isActive() const
 
 bool DrmGpu::needsModeset() const
 {
-    return std::any_of(m_pipelines.constBegin(), m_pipelines.constEnd(), [](const auto &pipeline) {
-        return pipeline->needsModeset();
-    });
+    return m_forceModeset || std::any_of(m_pipelines.constBegin(), m_pipelines.constEnd(), [](const auto &pipeline) {
+               return pipeline->needsModeset();
+           });
 }
 
 bool DrmGpu::maybeModeset()
@@ -771,6 +773,7 @@ bool DrmGpu::maybeModeset()
             }
         }
     }
+    m_forceModeset = false;
     if (err == DrmPipeline::Error::None) {
         return true;
     } else {
@@ -783,9 +786,6 @@ bool DrmGpu::maybeModeset()
 
 QList<DrmObject *> DrmGpu::unusedObjects() const
 {
-    if (!m_atomicModeSetting) {
-        return {};
-    }
     QList<DrmObject *> ret = m_allObjects;
     for (const auto &pipeline : m_pipelines) {
         ret.removeOne(pipeline->connector());

src/backends/drm/drm_gpu.h

@@ -143,6 +143,7 @@ private:
     bool m_asyncPageflipSupported = false;
     bool m_isRemoved = false;
     bool m_isActive = true;
+    bool m_forceModeset = false;
     clockid_t m_presentationClock;
     gbm_device *m_gbmDevice;
     FileDescriptor m_gbmFd;

src/backends/drm/drm_pipeline.cpp

@@ -118,7 +118,7 @@ DrmPipeline::Error DrmPipeline::commitPipelines(const QList<DrmPipeline *> &pipe
     if (pipelines[0]->gpu()->atomicModeSetting()) {
         return commitPipelinesAtomic(pipelines, mode, unusedObjects);
     } else {
-        return commitPipelinesLegacy(pipelines, mode);
+        return commitPipelinesLegacy(pipelines, mode, unusedObjects);
     }
 }
 

src/backends/drm/drm_pipeline.h

@@ -153,7 +153,7 @@ private:
     Error legacyModeset();
     Error applyPendingChangesLegacy();
     bool setCursorLegacy();
-    static Error commitPipelinesLegacy(const QList<DrmPipeline *> &pipelines, CommitMode mode);
+    static Error commitPipelinesLegacy(const QList<DrmPipeline *> &pipelines, CommitMode mode, const QList<DrmObject *> &unusedObjects);
 
     // atomic modesetting only
     Error prepareAtomicCommit(DrmAtomicCommit *commit, CommitMode mode);

src/backends/drm/drm_pipeline_legacy.cpp

@@ -57,7 +57,7 @@ DrmPipeline::Error DrmPipeline::legacyModeset()
     return Error::None;
 }
 
-DrmPipeline::Error DrmPipeline::commitPipelinesLegacy(const QList<DrmPipeline *> &pipelines, CommitMode mode)
+DrmPipeline::Error DrmPipeline::commitPipelinesLegacy(const QList<DrmPipeline *> &pipelines, CommitMode mode, const QList<DrmObject *> &unusedObjects)
 {
     Error err = Error::None;
     for (const auto &pipeline : pipelines) {
@@ -79,6 +79,11 @@ DrmPipeline::Error DrmPipeline::commitPipelinesLegacy(const QList<DrmPipeline *>
                 pipeline->pageFlipped(std::chrono::steady_clock::now().time_since_epoch(), PageflipType::Normal, PresentationMode::VSync);
             }
         }
+        for (const auto &obj : unusedObjects) {
+            if (auto crtc = dynamic_cast<DrmCrtc *>(obj)) {
+                drmModeSetCrtc(pipelines.front()->gpu()->fd(), crtc->id(), 0, 0, 0, nullptr, 0, nullptr);
+            }
+        }
     }
     return err;
 }