On 2018-11-05 09:24, Sean Paul wrote:
On Fri, Nov 02, 2018 at 04:38:48PM -0700, Jeykumar Sankaran wrote:
On 2018-11-01 12:18, Sean Paul wrote:
> On Wed, Oct 31, 2018 at 05:19:05PM -0700, Jeykumar Sankaran wrote:
> > msm maintains a separate structure to define vblank
> > work definitions and a list to track events submitted
> > to the display worker thread. We can avoid these
> > redundant list and its protection mechanism, if we
> > subclass the work object to encapsulate vblank
> > event parameters.
> >
> > Signed-off-by: Jeykumar Sankaran <jsanka@xxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/msm/msm_drv.c | 70
> ++++++++++++-------------------------------
> > drivers/gpu/drm/msm/msm_drv.h | 7 -----
> > 2 files changed, 19 insertions(+), 58 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c
> b/drivers/gpu/drm/msm/msm_drv.c
> > index 1f384b3..67a96ee 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
/snip
> > 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;
> > + kthread_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;
> >
> > - kthread_queue_work(&priv->disp_thread.worker, &vbl_ctrl->work);
> > + kthread_queue_work(&priv->disp_thread.worker, &vbl_work->work);
>
> So I think this can get even more simplified. In the short term, you
can
> just
> use the systemwq to do the enable and disable.
you mean priv->wq?
I meant the system workqueue, we probably don't need our own for this.
>
> In the long term, the enable_vblank/disable_vblank functions should be
> optimized so they don't sleep. I took a quick look at them perhaps
this
> is
> all because of the crtc_lock mutex? That lock seems a bit suspicious
to
> me,
> especially being dropped around the pm_runtime calls in
> _dpu_crtc_vblank_enable_no_lock(). I think we could probably rely on
the
> modeset
> locks for some of these functions, and perhaps convert it to a
spinlock
> if
> we
> can't get rid of it entirely.
crtc_lock has a history of usage in the downstream driver. It was
introduced
to protect
vblank variables when vblank requests were handled in the user thread
(not the display thread). When event threads were introduced to
receive
encoder events, the lock was further expanded to protect few more
vars.
It
was
also needed to synchronize CRTC accesses between debugfs dump calls
and display thread.
The debugfs case can be solved pretty easily by using the modeset
locks. I
haven't looked closely at the event threads, could we convert crtc_lock
to
a
spinlock and then make vblank enable/disable synchronous?
Did a little digging into the reason why vblank enable/disable was made
asynchronous
in the first place. Looks like Rob was also using priv->wq to queue
vblank requests
before display threads were introduced by the DPU driver.
The only reason I can think of was to support smart panels, where we
wait for
CTL_START interrupt instead of PING_PONG_DONE which is needed for fence
releases. Need to confirm with Rob for MDP5 behaviour before switcing to
sync.
For now, I submit a patch to use system wq.
Sean
Would like to deal with this cleanup bit later once we lose these
extra
threads.
Thanks and Regards,
Jeykumar S.
>
> Sean
>
> >
> > return 0;
> > }
> > @@ -269,20 +252,8 @@ 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.
> > - */
> > - kthread_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);
> > - }
> > -
> > kthread_flush_worker(&priv->disp_thread.worker);
> > kthread_stop(priv->disp_thread.thread);
> > priv->disp_thread.thread = NULL;
> > @@ -474,9 +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);
> > - kthread_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 e81b1fa..b91e306 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 kthread_work work;
> > - struct list_head event_list;
> > - spinlock_t lock;
> > -};
> > -
> > #define MSM_GPU_MAX_RINGS 4
> > #define MAX_H_TILES_PER_DISPLAY 2
> >
> > @@ -226,7 +220,6 @@ struct msm_drm_private {
> > struct notifier_block vmap_notifier;
> > struct shrinker shrinker;
> >
> > - struct msm_vblank_ctrl vblank_ctrl;
> > struct drm_atomic_state *pm_state;
> > };
> >
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
> > a Linux Foundation Collaborative Project
> >
> > _______________________________________________
> > Freedreno mailing list
> > Freedreno@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/freedreno
--
Jeykumar S
--
Jeykumar S
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