[PATCH 13/23] drm: omapdrm: Use a spinlock to protect the CRTC pending flag

[Laurent Pinchart]

The flag will need to be accessed atomically in the vblank interrupt
handler, memory barriers won't be enough.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 drivers/gpu/drm/omapdrm/omap_crtc.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c 
b/drivers/gpu/drm/omapdrm/omap_crtc.c
index f723db1096b1..ee744ab6608c 100644
--- a/drivers/gpu/drm/omapdrm/omap_crtc.c
+++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
@@ -68,6 +68,19 @@ enum omap_channel omap_crtc_channel(struct drm_crtc *crtc)
        return omap_crtc->channel;
 }

+static bool omap_crtc_is_pending(struct drm_crtc *crtc)
+{
+       struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
+       unsigned long flags;
+       bool pending;
+
+       spin_lock_irqsave(&crtc->dev->event_lock, flags);
+       pending = omap_crtc->pending;
+       spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
+
+       return pending;
+}
+
 int omap_crtc_wait_pending(struct drm_crtc *crtc)
 {
        struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
@@ -77,7 +90,7 @@ int omap_crtc_wait_pending(struct drm_crtc *crtc)
         * a single frame refresh even on slower displays.
         */
        return wait_event_timeout(omap_crtc->pending_wait,
-                                 !omap_crtc->pending,
+                                 !omap_crtc_is_pending(crtc),
                                  msecs_to_jiffies(250));
 }

@@ -294,6 +307,7 @@ static void omap_crtc_vblank_irq(struct omap_drm_irq *irq, 
uint32_t irqstatus)
        struct omap_crtc *omap_crtc =
                        container_of(irq, struct omap_crtc, vblank_irq);
        struct drm_device *dev = omap_crtc->base.dev;
+       struct drm_crtc *crtc = &omap_crtc->base;

        if (dispc_mgr_go_busy(omap_crtc->channel))
                return;
@@ -302,10 +316,10 @@ static void omap_crtc_vblank_irq(struct omap_drm_irq 
*irq, uint32_t irqstatus)

        __omap_irq_unregister(dev, &omap_crtc->vblank_irq);

-       rmb();
+       spin_lock(&crtc->dev->event_lock);
        WARN_ON(!omap_crtc->pending);
        omap_crtc->pending = false;
-       wmb();
+       spin_unlock(&crtc->dev->event_lock);

        /* wake up userspace */
        omap_crtc_complete_page_flip(&omap_crtc->base);
@@ -337,10 +351,10 @@ static void omap_crtc_enable(struct drm_crtc *crtc)

        DBG("%s", omap_crtc->name);

-       rmb();
+       spin_lock_irq(&crtc->dev->event_lock);
        WARN_ON(omap_crtc->pending);
        omap_crtc->pending = true;
-       wmb();
+       spin_unlock_irq(&crtc->dev->event_lock);

        omap_irq_register(crtc->dev, &omap_crtc->vblank_irq);

@@ -404,10 +418,10 @@ static void omap_crtc_atomic_flush(struct drm_crtc *crtc,

        DBG("%s: GO", omap_crtc->name);

-       rmb();
+       spin_lock_irq(&crtc->dev->event_lock);
        WARN_ON(omap_crtc->pending);
        omap_crtc->pending = true;
-       wmb();
+       spin_unlock_irq(&crtc->dev->event_lock);

        dispc_mgr_go(omap_crtc->channel);
        omap_irq_register(crtc->dev, &omap_crtc->vblank_irq);
-- 
2.7.3