From 6a055b92de15af987b4027826d43aa103c65a3c4 Mon Sep 17 00:00:00 2001
From: Lucas Stach <l.stach@pengutronix.de>
Date: Thu, 15 Mar 2018 10:11:59 +0100
Subject: [PATCH] drm/imx: move arming of the vblank event to atomic_flush
Git-commit: 6a055b92de15af987b4027826d43aa103c65a3c4
Patch-mainline: v4.16-rc7
References: bsc#1051510

Right now the vblank event completion is racing with the atomic update,
which is especially bad when the PRE is in use, as one of the hardware
issue workaround might extend the atomic commit for quite some time.

If the vblank IRQ happens to trigger during that time, we will prematurely
signal the atomic commit completion to userspace, which causes tearing
when userspace re-uses a framebuffer we haven't managed to flip away from
yet.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/imx/ipuv3-crtc.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -225,7 +225,11 @@ static void ipu_crtc_atomic_begin(struct
 				  struct drm_crtc_state *old_crtc_state)
 {
 	drm_crtc_vblank_on(crtc);
+}
 
+static void ipu_crtc_atomic_flush(struct drm_crtc *crtc,
+				  struct drm_crtc_state *old_crtc_state)
+{
 	spin_lock_irq(&crtc->dev->event_lock);
 	if (crtc->state->event) {
 		WARN_ON(drm_crtc_vblank_get(crtc));
@@ -293,6 +297,7 @@ static const struct drm_crtc_helper_func
 	.mode_set_nofb = ipu_crtc_mode_set_nofb,
 	.atomic_check = ipu_crtc_atomic_check,
 	.atomic_begin = ipu_crtc_atomic_begin,
+	.atomic_flush = ipu_crtc_atomic_flush,
 	.atomic_disable = ipu_crtc_atomic_disable,
 	.atomic_enable = ipu_crtc_atomic_enable,
 };