[PATCH v3 04/14] drm/rockchip: vop2: Send pending event when atomic_enable() fails

[Cristian Ciocaltea]

vop2_crtc_atomic_flush() stashes the CRTC completion event in vp->event
and relies on the frame start interrupt (VP_INT_FS_FIELD) to deliver it
later via drm_crtc_send_vblank_event().  Since atomic_enable() runs
before atomic_flush(), bailing on an error path makes it skip
drm_crtc_vblank_on() and leave the video port disabled.  atomic_flush()
still traps the event in vp->event, but since the port never scans out,
the frame start interrupt does not fire and the event is not delivered.
Userspace waiting for the flip completion then blocks indefinitely.

Note the event cannot be flushed from atomic_disable(), as userspace
waits for the completion before committing the next state, so the
disable does not arrive and draining it there would deadlock.

Use the newly added vp->enabled flag to detect this in atomic_flush()
and send the event immediately when the port did not come up, rather
than deferring it to an interrupt that will never occur.  This also
avoids the spurious drm_crtc_vblank_get() WARN previously hit on the
failed enable path, where the vblank is not on.

Fixes: 604be85547ce ("drm/rockchip: Add VOP2 driver")
Reported-by: Sashiko <sashiko-bot at kernel.org>
Closes: https://lore.kernel.org/all/20260706194935.AC7601F000E9@smtp.kernel.org/
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index 271c3cba6fb4..4bb1985b8726 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -2083,8 +2083,19 @@ static void vop2_crtc_atomic_flush(struct drm_crtc *crtc,
 	spin_lock_irq(&crtc->dev->event_lock);
 
 	if (crtc->state->event) {
-		WARN_ON(drm_crtc_vblank_get(crtc));
-		vp->event = crtc->state->event;
+		/*
+		 * A failed atomic_enable() leaves the video port disabled with
+		 * no scanout, so the frame start interrupt that normally
+		 * delivers vp->event never fires. Send the event right away in
+		 * that case to avoid stalling the flip completion.
+		 */
+		if (vp->enabled) {
+			WARN_ON(drm_crtc_vblank_get(crtc));
+			vp->event = crtc->state->event;
+		} else {
+			drm_crtc_send_vblank_event(crtc, crtc->state->event);
+		}
+
 		crtc->state->event = NULL;
 	}
 

-- 
2.54.0