platforms/drm: set DPMS property properly

src/plugins/platforms/drm/drm_object.cpp

@@ -305,7 +305,12 @@ bool DrmObject::Property::needsCommit() const
 
 bool DrmObject::Property::setPropertyLegacy(uint64_t value)
 {
-    return drmModeObjectSetProperty(m_obj->m_gpu->fd(), m_obj->id(), m_obj->m_objectType, m_propId, value) == 0;
+    if (drmModeObjectSetProperty(m_obj->m_gpu->fd(), m_obj->id(), m_obj->m_objectType, m_propId, value) == 0) {
+        m_current = m_next = m_pending = value;
+        return true;
+    } else {
+        return false;
+    }
 }
 
 void DrmObject::Property::initEnumMap(drmModePropertyRes *prop)

src/plugins/platforms/drm/drm_pipeline.cpp

@@ -260,6 +260,7 @@ bool DrmPipeline::modeset(int modeIndex)
         } else {
             m_crtc->setCurrent(m_primaryBuffer);
         }
+        m_connector->getProp(DrmConnector::PropertyIndex::Dpms)->setCurrent(DRM_MODE_DPMS_ON);
     }
     return true;
 }