[PATCH 2/2] drm/vc4: Fix drm_vblank_put/get imbalance in page flip path.

[Mario Kleiner]

The async page flip path was missing drm_crtc_vblank_get/put
completely. The sync flip path was missing a vblank put, so async
flips only reported proper pageflip completion events by chance,
and vblank irq's never turned off after a first vsync'ed page flip
until system reboot.

Tested against Raspian kernel 4.4.8 tree on RPi 2B.

Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Cc: Eric Anholt <eric at anholt.net>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 355ee4b..c3854e2 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -456,6 +456,7 @@ static void vc4_crtc_handle_page_flip(struct vc4_crtc 
*vc4_crtc)
        if (vc4_crtc->event) {
                drm_crtc_send_vblank_event(crtc, vc4_crtc->event);
                vc4_crtc->event = NULL;
+               drm_crtc_vblank_put(crtc);
        }
        spin_unlock_irqrestore(&dev->event_lock, flags);
 }
@@ -506,6 +507,7 @@ vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
                spin_unlock_irqrestore(&dev->event_lock, flags);
        }

+       drm_crtc_vblank_put(crtc);
        drm_framebuffer_unreference(flip_state->fb);
        kfree(flip_state);

@@ -548,6 +550,8 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
                return ret;
        }

+       WARN_ON(drm_crtc_vblank_get(crtc) != 0);
+
        /* Immediately update the plane's legacy fb pointer, so that later
         * modeset prep sees the state that will be present when the semaphore
         * is released.
-- 
2.7.0