Re: [Freedreno] [PATCH v2 5/5] drm/msm: subclass work object for vblank events

Jeykumar Sankaran <jsanka@xxxxxxxxxxxxxx> · Thu, 06 Dec 2018 18:32:09 -0800

On 2018-12-06 10:56, Jeykumar Sankaran wrote:
On 2018-11-07 07:55, Sean Paul wrote:
On Tue, Nov 06, 2018 at 02:36:30PM -0800, Jeykumar Sankaran wrote:
msm maintains a separate structure to define vblank
work definitions and a list to track events submitted
to the workqueue. We can avoid this redundant list
and its protection mechanism, if we subclass the
work object to encapsulate vblank event parameters.

changes in v2:
	- subclass optimization on system wq (Sean Paul)

I wouldn't do it like this, tbh. One problem is that you've lost your
flush() on
unbind, so there's no way to know if you have workers in the wild 
waiting
to
enable/disable vblank.

I believe I didnt respond to this quesition of yours. This patch is
removing the flush on the work. But flush_workqueue before destroying 
the WQ
will make sure all the queued work jobs are run to completion.

To honor the comment, I will fix the patch to move the flush/destroy
wq before the
irq_unininstall.

Above is possible if we use priv->wq for vblank requests. Posted v4 with
the above fixes.

Thanks,
Jeykumar S.

Another issues is that AFAICT, we don't need a queue of 
enables/disables,
but
rather just the last requested state (ie: should we be on or off). So
things
don't need to be this complicated (and we're possibly thrashing vblank
on/off
for no reason).

I'm still of the mind that you should just make this synchronous and 
be
done
with the threads (especially since we're still uncovering/introducing
races!).

Sean


Signed-off-by: Jeykumar Sankaran <jsanka@xxxxxxxxxxxxxx>
---
 drivers/gpu/drm/msm/msm_drv.c | 67
+++++++++++++------------------------------
 drivers/gpu/drm/msm/msm_drv.h |  7 -----
 2 files changed, 20 insertions(+), 54 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c
b/drivers/gpu/drm/msm/msm_drv.c
index 6d6c73b..8da5be2 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -203,61 +203,44 @@ u32 msm_readl(const void __iomem *addr)
 	return val;
 }

-struct vblank_event {
-	struct list_head node;
+struct msm_vblank_work {
+	struct work_struct work;
 	int crtc_id;
 	bool enable;
+	struct msm_drm_private *priv;
 };

 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_vblank_work *vbl_work = container_of(work,
+						struct msm_vblank_work,
work);
+	struct msm_drm_private *priv = vbl_work->priv;
 	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);
-	}
+	if (vbl_work->enable)
+		kms->funcs->enable_vblank(kms,
priv->crtcs[vbl_work->crtc_id]);
+	else
+		kms->funcs->disable_vblank(kms,
priv->crtcs[vbl_work->crtc_id]);

-	spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
+	kfree(vbl_work);
 }

 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;
+	struct msm_vblank_work *vbl_work;

-	vbl_ev = kzalloc(sizeof(*vbl_ev), GFP_ATOMIC);
-	if (!vbl_ev)
+	vbl_work = kzalloc(sizeof(*vbl_work), GFP_ATOMIC);
+	if (!vbl_work)
 		return -ENOMEM;

-	vbl_ev->crtc_id = crtc_id;
-	vbl_ev->enable = enable;
+	INIT_WORK(&vbl_work->work, vblank_ctrl_worker);

-	spin_lock_irqsave(&vbl_ctrl->lock, flags);
-	list_add_tail(&vbl_ev->node, &vbl_ctrl->event_list);
-	spin_unlock_irqrestore(&vbl_ctrl->lock, flags);
+	vbl_work->crtc_id = crtc_id;
+	vbl_work->enable = enable;
+	vbl_work->priv = priv;

-	schedule_work(&vbl_ctrl->work);
+	schedule_work(&vbl_work->work);

 	return 0;
 }
@@ -269,14 +252,13 @@ static int msm_drm_uninit(struct device *dev)
 	struct msm_drm_private *priv = ddev->dev_private;
 	struct msm_kms *kms = priv->kms;
 	struct msm_mdss *mdss = priv->mdss;
-	struct msm_vblank_ctrl *vbl_ctrl = &priv->vblank_ctrl;
-	struct vblank_event *vbl_ev, *tmp;
 	int i;

 	/* 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.
 	 */
+
 	msm_gem_shrinker_cleanup(ddev);

 	drm_kms_helper_poll_fini(ddev);
@@ -292,12 +274,6 @@ static int msm_drm_uninit(struct device *dev)
 #endif
 	drm_mode_config_cleanup(ddev);

-	flush_work(&vbl_ctrl->work);
-	list_for_each_entry_safe(vbl_ev, tmp, &vbl_ctrl->event_list, node)
{
-		list_del(&vbl_ev->node);
-		kfree(vbl_ev);
-	}
-
 	/* clean up event worker threads */
 	for (i = 0; i < priv->num_crtcs; i++) {
 		if (priv->event_thread[i].thread) {
@@ -469,9 +445,6 @@ static int msm_drm_init(struct device *dev, 
struct
drm_driver *drv)
 	priv->wq = alloc_ordered_workqueue("msm", 0);

 	INIT_LIST_HEAD(&priv->inactive_list);
-	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(ddev);

diff --git a/drivers/gpu/drm/msm/msm_drv.h
b/drivers/gpu/drm/msm/msm_drv.h
index 05d33a7..d4cbde2 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -77,12 +77,6 @@ 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;
-};
-
 #define MSM_GPU_MAX_RINGS 4
 #define MAX_H_TILES_PER_DISPLAY 2

@@ -225,7 +219,6 @@ struct msm_drm_private {
 	struct notifier_block vmap_notifier;
 	struct shrinker shrinker;

-	struct msm_vblank_ctrl vblank_ctrl;
 	struct drm_atomic_state *pm_state;
 };

--
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--
Jeykumar S






