Use a timer for unreferencing the all-black FB

The timer fires 1 second after LeaveVT. This gives the next DRM master
enough time to set up scanout of its own buffers.

Fixes prolonged intermittent black screen when switching from Xorg to
e.g. the GDM Wayland mode login VT.

Fixes: 06a465484101 ("Make all active CRTCs scan out an all-black
                      framebuffer in LeaveVT")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 27 insertions, 13 deletions

diff --git a/src/radeon_kms.c b/src/radeon_kms.c
index 5410c420..01594c6c 100644
--- a/src/radeon_kms.c
+++ b/src/radeon_kms.c
@@ -1150,7 +1150,6 @@ static void RADEONBlockHandler_KMS(BLOCKHANDLER_ARGS_DECL)
 {
     SCREEN_PTR(arg);
     ScrnInfoPtr    pScrn   = xf86ScreenToScrn(pScreen);
-    RADEONEntPtr pRADEONEnt = RADEONEntPriv(pScrn);
     RADEONInfoPtr  info    = RADEONPTR(pScrn);
     xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(pScrn);
     int c;
@@ -1159,19 +1158,8 @@ static void RADEONBlockHandler_KMS(BLOCKHANDLER_ARGS_DECL)
     (*pScreen->BlockHandler) (BLOCKHANDLER_ARGS);
     pScreen->BlockHandler = RADEONBlockHandler_KMS;
 
-    if (!xf86ScreenToScrn(radeon_master_screen(pScreen))->vtSema) {
-	/* Unreference the all-black FB created by RADEONLeaveVT_KMS. After
-	 * this, there should be no FB left created by this driver.
-	 */
-	for (c = 0; c < xf86_config->num_crtc; c++) {
-	    drmmode_crtc_private_ptr drmmode_crtc =
-		xf86_config->crtc[c]->driver_private;
-
-	    drmmode_fb_reference(pRADEONEnt->fd, &drmmode_crtc->fb, NULL);
-	}
-
+    if (!xf86ScreenToScrn(radeon_master_screen(pScreen))->vtSema)
 	return;
-    }
 
     if (!radeon_is_gpu_screen(pScreen))
     {
@@ -2473,6 +2461,30 @@ Bool RADEONEnterVT_KMS(VT_FUNC_ARGS_DECL)
     return TRUE;
 }
 
+static
+CARD32 cleanup_black_fb(OsTimerPtr timer, CARD32 now, pointer data)
+{
+    ScreenPtr screen = data;
+    ScrnInfoPtr scrn = xf86ScreenToScrn(screen);
+    RADEONEntPtr pRADEONEnt = RADEONEntPriv(scrn);
+    xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(scrn);
+    int c;
+
+    if (xf86ScreenToScrn(radeon_master_screen(screen))->vtSema)
+	return 0;
+
+    /* Unreference the all-black FB created by RADEONLeaveVT_KMS. After
+     * this, there should be no FB left created by this driver.
+     */
+    for (c = 0; c < xf86_config->num_crtc; c++) {
+	drmmode_crtc_private_ptr drmmode_crtc =
+	    xf86_config->crtc[c]->driver_private;
+
+	drmmode_fb_reference(pRADEONEnt->fd, &drmmode_crtc->fb, NULL);
+    }
+
+    return 0;
+}
 
 static void
 pixmap_unref_fb(void *value, XID id, void *cdata)
@@ -2569,6 +2581,8 @@ void RADEONLeaveVT_KMS(VT_FUNC_ARGS_DECL)
     }
     pixmap_unref_fb(pScreen->GetScreenPixmap(pScreen), None, pRADEONEnt);
 
+    TimerSet(NULL, 0, 1000, cleanup_black_fb, pScreen);
+
     xf86_hide_cursors (pScrn);
 
     radeon_drop_drm_master(pScrn);