drm/msm: Enable clocks during enable/disable_vblank() callbacks

AHB clock should be enabled before accessing registers during
enable/disable_vblank(). Since these 2 callbacks are called in
atomic context while clk_prepare may cause thread sleep, a work
is scheduled to control vblanks.

v2: fixup spinlock initialization

Signed-off-by: Hai Li <hali@codeaurora.org>
[add comment about cancel_work_sync() before drm_irq_uninstall()]
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/mdp/mdp4/mdp4_irq.c

@@ -86,13 +86,22 @@ irqreturn_t mdp4_irq(struct msm_kms *kms)
 
 int mdp4_enable_vblank(struct msm_kms *kms, struct drm_crtc *crtc)
 {
+	struct mdp4_kms *mdp4_kms = to_mdp4_kms(to_mdp_kms(kms));
+
+	mdp4_enable(mdp4_kms);
 	mdp_update_vblank_mask(to_mdp_kms(kms),
 			mdp4_crtc_vblank(crtc), true);
+	mdp4_disable(mdp4_kms);
+
 	return 0;
 }
 
 void mdp4_disable_vblank(struct msm_kms *kms, struct drm_crtc *crtc)
 {
+	struct mdp4_kms *mdp4_kms = to_mdp4_kms(to_mdp_kms(kms));
+
+	mdp4_enable(mdp4_kms);
 	mdp_update_vblank_mask(to_mdp_kms(kms),
 			mdp4_crtc_vblank(crtc), false);
+	mdp4_disable(mdp4_kms);
 }

drivers/gpu/drm/msm/mdp/mdp5/mdp5_irq.c

@@ -112,15 +112,24 @@ irqreturn_t mdp5_irq(struct msm_kms *kms)
 
 int mdp5_enable_vblank(struct msm_kms *kms, struct drm_crtc *crtc)
 {
+	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(kms));
+
+	mdp5_enable(mdp5_kms);
 	mdp_update_vblank_mask(to_mdp_kms(kms),
 			mdp5_crtc_vblank(crtc), true);
+	mdp5_disable(mdp5_kms);
+
 	return 0;
 }
 
 void mdp5_disable_vblank(struct msm_kms *kms, struct drm_crtc *crtc)
 {
+	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(kms));
+
+	mdp5_enable(mdp5_kms);
 	mdp_update_vblank_mask(to_mdp_kms(kms),
 			mdp5_crtc_vblank(crtc), false);
+	mdp5_disable(mdp5_kms);
 }
 
 /*

drivers/gpu/drm/msm/msm_drv.c

@@ -116,6 +116,65 @@ u32 msm_readl(const void __iomem *addr)
 	return val;
 }
 
+struct vblank_event {
+	struct list_head node;
+	int crtc_id;
+	bool enable;
+};
+
+static void vblank_ctrl_worker(struct work_struct *work)
+{
+	struct msm_vblank_ctrl *vbl_ctrl = container_of(work,
+						struct msm_vblank_ctrl, work);
+	struct msm_drm_private *priv = container_of(vbl_ctrl,
+					struct msm_drm_private, vblank_ctrl);
+	struct msm_kms *kms = priv->kms;
+	struct vblank_event *vbl_ev, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&vbl_ctrl->lock, flags);
+	list_for_each_entry_safe(vbl_ev, tmp, &vbl_ctrl->event_list, node) {
+		list_del(&vbl_ev->node);
+		spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
+
+		if (vbl_ev->enable)
+			kms->funcs->enable_vblank(kms,
+						priv->crtcs[vbl_ev->crtc_id]);
+		else
+			kms->funcs->disable_vblank(kms,
+						priv->crtcs[vbl_ev->crtc_id]);
+
+		kfree(vbl_ev);
+
+		spin_lock_irqsave(&vbl_ctrl->lock, flags);
+	}
+
+	spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
+}
+
+static int vblank_ctrl_queue_work(struct msm_drm_private *priv,
+					int crtc_id, bool enable)
+{
+	struct msm_vblank_ctrl *vbl_ctrl = &priv->vblank_ctrl;
+	struct vblank_event *vbl_ev;
+	unsigned long flags;
+
+	vbl_ev = kzalloc(sizeof(*vbl_ev), GFP_ATOMIC);
+	if (!vbl_ev)
+		return -ENOMEM;
+
+	vbl_ev->crtc_id = crtc_id;
+	vbl_ev->enable = enable;
+
+	spin_lock_irqsave(&vbl_ctrl->lock, flags);
+	list_add_tail(&vbl_ev->node, &vbl_ctrl->event_list);
+	spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
+
+	queue_work(priv->wq, &vbl_ctrl->work);
+
+	return 0;
+}
+
 /*
  * DRM operations:
  */
@@ -125,6 +184,18 @@ static int msm_unload(struct drm_device *dev)
 	struct msm_drm_private *priv = dev->dev_private;
 	struct msm_kms *kms = priv->kms;
 	struct msm_gpu *gpu = priv->gpu;
+	struct msm_vblank_ctrl *vbl_ctrl = &priv->vblank_ctrl;
+	struct vblank_event *vbl_ev, *tmp;
+
+	/* We must cancel and cleanup any pending vblank enable/disable
+	 * work before drm_irq_uninstall() to avoid work re-enabling an
+	 * irq after uninstall has disabled it.
+	 */
+	cancel_work_sync(&vbl_ctrl->work);
+	list_for_each_entry_safe(vbl_ev, tmp, &vbl_ctrl->event_list, node) {
+		list_del(&vbl_ev->node);
+		kfree(vbl_ev);
+	}
 
 	drm_kms_helper_poll_fini(dev);
 	drm_mode_config_cleanup(dev);
@@ -282,6 +353,9 @@ static int msm_load(struct drm_device *dev, unsigned long flags)
 
 	INIT_LIST_HEAD(&priv->inactive_list);
 	INIT_LIST_HEAD(&priv->fence_cbs);
+	INIT_LIST_HEAD(&priv->vblank_ctrl.event_list);
+	INIT_WORK(&priv->vblank_ctrl.work, vblank_ctrl_worker);
+	spin_lock_init(&priv->vblank_ctrl.lock);
 
 	drm_mode_config_init(dev);
 
@@ -464,7 +538,7 @@ static int msm_enable_vblank(struct drm_device *dev, int crtc_id)
 	if (!kms)
 		return -ENXIO;
 	DBG("dev=%p, crtc=%d", dev, crtc_id);
-	return kms->funcs->enable_vblank(kms, priv->crtcs[crtc_id]);
+	return vblank_ctrl_queue_work(priv, crtc_id, true);
 }
 
 static void msm_disable_vblank(struct drm_device *dev, int crtc_id)
@@ -474,7 +548,7 @@ static void msm_disable_vblank(struct drm_device *dev, int crtc_id)
 	if (!kms)
 		return;
 	DBG("dev=%p, crtc=%d", dev, crtc_id);
-	kms->funcs->disable_vblank(kms, priv->crtcs[crtc_id]);
+	vblank_ctrl_queue_work(priv, crtc_id, false);
 }
 
 /*

drivers/gpu/drm/msm/msm_drv.h

@@ -71,6 +71,12 @@ enum msm_mdp_plane_property {
 	PLANE_PROP_MAX_NUM
 };
 
+struct msm_vblank_ctrl {
+	struct work_struct work;
+	struct list_head event_list;
+	spinlock_t lock;
+};
+
 struct msm_drm_private {
 
 	struct msm_kms *kms;
@@ -147,6 +153,8 @@ struct msm_drm_private {
 		 */
 		struct drm_mm mm;
 	} vram;
+
+	struct msm_vblank_ctrl vblank_ctrl;
 };
 
 struct msm_format {