[PATCH xf86-video-amdgpu] Use a timer for unreferencing the all-black FB

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

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: c16ff42f927d ("Make all active CRTCs scan out an all-black
                      framebuffer in LeaveVT")
(Ported from radeon commit 9d9c565c84601f4c6c73ad769f86491088683f7a)

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 src/amdgpu_kms.c | 42 +++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/src/amdgpu_kms.c b/src/amdgpu_kms.c
index c3613eb8d..d82ead2ac 100644
--- a/src/amdgpu_kms.c
+++ b/src/amdgpu_kms.c
@@ -1044,7 +1044,6 @@ static void AMDGPUBlockHandler_KMS(BLOCKHANDLER_ARGS_DECL)
 {
 	SCREEN_PTR(arg);
 	ScrnInfoPtr pScrn = xf86ScreenToScrn(pScreen);
-	AMDGPUEntPtr pAMDGPUEnt = AMDGPUEntPriv(pScrn);
 	AMDGPUInfoPtr info = AMDGPUPTR(pScrn);
 	xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(pScrn);
 	int c;
@@ -1053,21 +1052,8 @@ static void AMDGPUBlockHandler_KMS(BLOCKHANDLER_ARGS_DECL)
 	(*pScreen->BlockHandler) (BLOCKHANDLER_ARGS);
 	pScreen->BlockHandler = AMDGPUBlockHandler_KMS;
 
-	if (!xf86ScreenToScrn(amdgpu_master_screen(pScreen))->vtSema) {
-		/* Unreference the all-black FB created by AMDGPULeaveVT_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(pAMDGPUEnt->fd, &drmmode_crtc->fb,
-					     NULL);
-		}
-
+	if (!xf86ScreenToScrn(amdgpu_master_screen(pScreen))->vtSema)
 		return;
-	}
 
 	if (!amdgpu_is_gpu_screen(pScreen))
 	{
@@ -1629,6 +1615,30 @@ static void amdgpu_drop_drm_master(ScrnInfoPtr pScrn)
 }
 
 
+static
+CARD32 cleanup_black_fb(OsTimerPtr timer, CARD32 now, pointer data)
+{
+	ScreenPtr screen = data;
+	ScrnInfoPtr scrn = xf86ScreenToScrn(screen);
+	AMDGPUEntPtr pAMDGPUEnt = AMDGPUEntPriv(scrn);
+	xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(scrn);
+	int c;
+
+	if (xf86ScreenToScrn(amdgpu_master_screen(screen))->vtSema)
+		return 0;
+
+	/* Unreference the all-black FB created by AMDGPULeaveVT_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(pAMDGPUEnt->fd, &drmmode_crtc->fb, NULL);
+	}
+
+	return 0;
+}
 
 static Bool AMDGPUSaveScreen_KMS(ScreenPtr pScreen, int mode)
 {
@@ -2061,6 +2071,8 @@ void AMDGPULeaveVT_KMS(VT_FUNC_ARGS_DECL)
 	}
 	pixmap_unref_fb(pScreen->GetScreenPixmap(pScreen), None, pAMDGPUEnt);
 
+	TimerSet(NULL, 0, 1000, cleanup_black_fb, pScreen);
+
 	xf86_hide_cursors(pScrn);
 
 	amdgpu_drop_drm_master(pScrn);
-- 
2.14.1