[PATCH v2 3/4] drm/exynos: fix lockdep for event_lock wrt. vbl_time_lock

[Imre Deak]

Currently the exynos driver calls drm_vblank_off() with the event_lock
held, while drm_vblank_off() will lock vbl_time and vblank_time_lock.
This lock dependency chain conflicts with the one in drm_handle_vblank()
where we first lock vblank_time_lock and then the event_lock.

Fix this by removing the above drm_vblank_off() calls which are in fact
never executed: drm_dev->vblank_disable_allowed is only ever non-zero
during driver init, until it's set in {fimd,vidi}_subdrv_probe. Both the
driver init and open code is protected by drm_global_mutex, so the
earliest page flip ioctl can happen only after vblank_disable_allowed is
set to 1. Thus {fimd,vidi}_finish_pageflip - with pending flip events -
will always get called with vblank_disable_allowed being 1.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/exynos/exynos_drm_fimd.c |   12 ------------
 drivers/gpu/drm/exynos/exynos_drm_vidi.c |   12 ------------
 2 files changed, 24 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
index e69b7c4..2eb131c 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
@@ -623,7 +623,6 @@ static void fimd_finish_pageflip(struct drm_device *drm_dev, int crtc)
 	struct drm_pending_vblank_event *e, *t;
 	struct timeval now;
 	unsigned long flags;
-	bool is_checked = false;
 
 	spin_lock_irqsave(&drm_dev->event_lock, flags);
 
@@ -633,8 +632,6 @@ static void fimd_finish_pageflip(struct drm_device *drm_dev, int crtc)
 		if (crtc != e->pipe)
 			continue;
 
-		is_checked = true;
-
 		do_gettimeofday(&now);
 		e->event.sequence = 0;
 		e->event.tv_sec = now.tv_sec;
@@ -645,15 +642,6 @@ static void fimd_finish_pageflip(struct drm_device *drm_dev, int crtc)
 		drm_vblank_put(drm_dev, crtc);
 	}
 
-	if (is_checked) {
-		/*
-		 * don't off vblank if vblank_disable_allowed is 1,
-		 * because vblank would be off by timer handler.
-		 */
-		if (!drm_dev->vblank_disable_allowed)
-			drm_vblank_off(drm_dev, crtc);
-	}
-
 	spin_unlock_irqrestore(&drm_dev->event_lock, flags);
 }
 
diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index e26d455..4b0c16b 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -382,7 +382,6 @@ static void vidi_finish_pageflip(struct drm_device *drm_dev, int crtc)
 	struct drm_pending_vblank_event *e, *t;
 	struct timeval now;
 	unsigned long flags;
-	bool is_checked = false;
 
 	spin_lock_irqsave(&drm_dev->event_lock, flags);
 
@@ -392,8 +391,6 @@ static void vidi_finish_pageflip(struct drm_device *drm_dev, int crtc)
 		if (crtc != e->pipe)
 			continue;
 
-		is_checked = true;
-
 		do_gettimeofday(&now);
 		e->event.sequence = 0;
 		e->event.tv_sec = now.tv_sec;
@@ -404,15 +401,6 @@ static void vidi_finish_pageflip(struct drm_device *drm_dev, int crtc)
 		drm_vblank_put(drm_dev, crtc);
 	}
 
-	if (is_checked) {
-		/*
-		 * don't off vblank if vblank_disable_allowed is 1,
-		 * because vblank would be off by timer handler.
-		 */
-		if (!drm_dev->vblank_disable_allowed)
-			drm_vblank_off(drm_dev, crtc);
-	}
-
 	spin_unlock_irqrestore(&drm_dev->event_lock, flags);
 }
 
-- 
1.7.9.5