eglfs: kms: Make threaded atomic drm work

The atomic modesetting support was not prepared for page flips being
issued from different (per-screen) threads.

This could be seen with the threaded render loop of Qt Quick: having a
QQuickWindow per screen means having a dedicated render thread for each
screen. QKmsDevice used simply instance variables to keep track of the
request. This leads to the commit failing with EBUSY sooner or later.

Make the atomic request and related variables thread local.

This prevents failing drmModeAtomicCommit() with 2 or more screens and
the threaded render loop. It does not fix other potential issues when
waiting for page flips to complete, that is to be tackled separately.

Task-number: QTBUG-74953
Change-Id: I2dac10d5e9bdc0cb556ac78c9643c96d40d692e4
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

2 files changed, 8 insertions, 10 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
index 16dbfe1522..333433f666 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
@@ -243,7 +243,7 @@ void QEglFSKmsGbmScreen::ensureModeSet(uint32_t fb)
 
             if (device()->hasAtomicSupport()) {
 #if QT_CONFIG(drm_atomic)
-                drmModeAtomicReq *request = device()->atomic_request();
+                drmModeAtomicReq *request = device()->threadLocalAtomicRequest();
                 if (request) {
                     drmModeAtomicAddProperty(request, op.connector_id, op.crtcIdPropertyId, op.crtc_id);
                     drmModeAtomicAddProperty(request, op.crtc_id, op.modeIdPropertyId, op.mode_blob_id);
@@ -287,8 +287,7 @@ void QEglFSKmsGbmScreen::waitForFlip()
     }
 
 #if QT_CONFIG(drm_atomic)
-    if (device()->hasAtomicSupport())
-        device()->atomicReset();
+    device()->threadLocalAtomicReset();
 #endif
 }
 
@@ -324,16 +323,16 @@ void QEglFSKmsGbmScreen::flip()
 
     if (device()->hasAtomicSupport()) {
 #if QT_CONFIG(drm_atomic)
-        drmModeAtomicReq *request = device()->atomic_request();
+        drmModeAtomicReq *request = device()->threadLocalAtomicRequest();
         if (request) {
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->framebufferPropertyId, fb->fb);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->crtcPropertyId, op.crtc_id);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->srcwidthPropertyId,
-                                     output().size.width() << 16);
+                                     op.size.width() << 16);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->srcXPropertyId, 0);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->srcYPropertyId, 0);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->srcheightPropertyId,
-                                     output().size.height() << 16);
+                                     op.size.height() << 16);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->crtcXPropertyId, 0);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->crtcYPropertyId, 0);
             drmModeAtomicAddProperty(request, op.eglfs_plane->id, op.eglfs_plane->crtcwidthPropertyId,
@@ -371,7 +370,7 @@ void QEglFSKmsGbmScreen::flip()
 
             if (device()->hasAtomicSupport()) {
 #if QT_CONFIG(drm_atomic)
-                drmModeAtomicReq *request = device()->atomic_request();
+                drmModeAtomicReq *request = device()->threadLocalAtomicRequest();
                 if (request) {
                     drmModeAtomicAddProperty(request, d.screen->output().eglfs_plane->id,
                                                       d.screen->output().eglfs_plane->framebufferPropertyId, fb->fb);
@@ -394,8 +393,7 @@ void QEglFSKmsGbmScreen::flip()
     }
 
 #if QT_CONFIG(drm_atomic)
-    if (device()->hasAtomicSupport())
-         device()->atomicCommit(this);
+    device()->threadLocalAtomicCommit(this);
 #endif
 }
 
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.cpp
index a6aac61506..28b6b7df63 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.cpp
@@ -140,7 +140,7 @@ void *QEglFSKmsIntegration::nativeResourceForIntegration(const QByteArray &name)
 
 #if QT_CONFIG(drm_atomic)
     if (name == QByteArrayLiteral("dri_atomic_request") && m_device)
-        return (void *) (qintptr) m_device->atomic_request();
+        return (void *) (qintptr) m_device->threadLocalAtomicRequest();
 #endif
     return nullptr;
 }