eglfs_kms: Do not skip the initial SetCrtc

Trying to be clever seems to cause issues on some systems, for example
AMD (RADV) on Ubuntu 20.04 gives totally garbled output by default.

Remove the undocumented ALWAYS_SET_MODE env.var. as well, it won't have
much of a purpose since we'll in effect hit the SetCrtc path always now
once on startup.

Change-Id: Ibaa463ff913eb0c1251d6d3435aa4799fe5c8a29
Fixes: QTBUG-85797
Pick-to: 5.15
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 3 insertions, 8 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
index efb0b1b060..8330a97f94 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
@@ -227,16 +227,11 @@ void QEglFSKmsGbmScreen::ensureModeSet(uint32_t fb)
 
         bool doModeSet = true;
         drmModeCrtcPtr currentMode = drmModeGetCrtc(fd, op.crtc_id);
-        const bool alreadySet = currentMode && !memcmp(&currentMode->mode, &op.modes[op.mode], sizeof(drmModeModeInfo));
+        const bool alreadySet = currentMode && currentMode->buffer_id == fb && !memcmp(&currentMode->mode, &op.modes[op.mode], sizeof(drmModeModeInfo));
         if (currentMode)
             drmModeFreeCrtc(currentMode);
-        if (alreadySet) {
-            static bool alwaysDoSet = qEnvironmentVariableIntValue("QT_QPA_EGLFS_ALWAYS_SET_MODE");
-            if (!alwaysDoSet) {
-                qCDebug(qLcEglfsKmsDebug, "Mode already set, skipping modesetting for screen %s", qPrintable(name()));
-                doModeSet = false;
-            }
-        }
+        if (alreadySet)
+            doModeSet = false;
 
         if (doModeSet) {
             qCDebug(qLcEglfsKmsDebug, "Setting mode for screen %s", qPrintable(name()));