Re: [PATCH] drm/msm/dp: stop event kernel thread when DP unbind

[Dmitry Baryshkov]

On 12/04/2022 03:21, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2022-04-11 17:08:49)
> > Current DP driver implementation, event thread is kept running
> > after DP display is unbind. This patch fix this problem by disabling
> > DP irq and stop event thread to exit gracefully at dp_display_unbind().
> >
> > Fixes: e91e3065a806 ("drm/msm/dp: Add DP compliance tests on Snapdragon Chipsets")
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
>
> Should add a Reported-by tag from Dmitry here.
>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_display.c | 24 ++++++++++++++++++++++--
> >   1 file changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 01453db..fa1ef8e 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -273,6 +274,8 @@ static int dp_display_bind(struct device *dev, struct device *master,
> >          return rc;
> >   }
> >
> > +static void dp_hpd_event_stop(struct dp_display_private *dp_priv);
>
> Why can't the function be defined here?
>
> > +
> >   static void dp_display_unbind(struct device *dev, struct device *master,
> >                                void *data)
> >   {
> > @@ -280,6 +283,8 @@ static void dp_display_unbind(struct device *dev, struct device *master,
> >          struct drm_device *drm = dev_get_drvdata(master);
> >          struct msm_drm_private *priv = drm->dev_private;
> >
> > +       disable_irq(dp->irq);
> > +       dp_hpd_event_stop(dp);
> >          dp_power_client_deinit(dp->power);
> >          dp_aux_unregister(dp->aux);
> >          priv->dp[dp->id] = NULL;
> > @@ -1054,7 +1059,7 @@ static int hpd_event_thread(void *data)
> >
> >          dp_priv = (struct dp_display_private *)data;
> >
> > -       while (1) {
> > +       while (!kthread_should_stop()) {
> >                  if (timeout_mode) {
> >                          wait_event_timeout(dp_priv->event_q,
> >                                  (dp_priv->event_pndx == dp_priv->event_gndx),
> > @@ -1137,7 +1142,22 @@ static void dp_hpd_event_setup(struct dp_display_private *dp_priv)
> >          init_waitqueue_head(&dp_priv->event_q);
> >          spin_lock_init(&dp_priv->event_lock);
> >
> > -       kthread_run(hpd_event_thread, dp_priv, "dp_hpd_handler");
> > +       dp_priv->ev_tsk = kthread_run(hpd_event_thread, dp_priv, "dp_hpd_handler");
> > +
> > +       if (IS_ERR(dp_priv->ev_tsk))
> > +               DRM_ERROR("failed to create DP event thread\n");
>
> Why can't we error out? Why can't this kthread be started in probe?

Just my 2c. I don't think starting it in probe is a good idea. The 
driver uses components, so, in my opinion, the thread should be started 
from bind and stopped in unbind.

> > +}
> > +
> > +static void dp_hpd_event_stop(struct dp_display_private *dp_priv)
> > +{
> > +       if (IS_ERR(dp_priv->ev_tsk))
> > +               return;
> > +
> > +       kthread_stop(dp_priv->ev_tsk);
> > +
> > +       /* reset event q to empty */
> > +       dp_priv->event_gndx = 0;
> > +       dp_priv->event_pndx = 0;
> >   }


--
With best wishes
Dmitry