[PATCH] drm/mediatek: Add spinlock for setting vblank event in atomic_begin

[Jason-JH . Lin]

Add spinlock protection to avoid race condition on vblank event
between mtk_drm_crtc_atomic_begin() and mtk_drm_finish_page_flip().

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Signed-off-by: Jason-JH.Lin <jason-jh....@mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c 
b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
index d40142842f85..128a672fe3c9 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
@@ -746,6 +746,9 @@ static void mtk_drm_crtc_atomic_begin(struct drm_crtc *crtc,
                                                                          crtc);
        struct mtk_crtc_state *mtk_crtc_state = to_mtk_crtc_state(crtc_state);
        struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
+       unsigned long flags;
+
+       spin_lock_irqsave(&crtc->dev->event_lock, flags);
 
        if (mtk_crtc->event && mtk_crtc_state->base.event)
                DRM_ERROR("new event while there is still a pending event\n");
@@ -756,6 +759,8 @@ static void mtk_drm_crtc_atomic_begin(struct drm_crtc *crtc,
                mtk_crtc->event = mtk_crtc_state->base.event;
                mtk_crtc_state->base.event = NULL;
        }
+
+       spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
 }
 
 static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
-- 
2.18.0