Re: [PATCH v7] drm/msm/dp: stop event kernel thread when DP unbind

[Kuogee Hsieh]

On 4/15/2022 3:48 PM, Dmitry Baryshkov wrote:
> On Sat, 16 Apr 2022 at 01:34, Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> wrote:
> > 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().
> >
> > Changes in v2:
> > -- start event thread at dp_display_bind()
> >
> > Changes in v3:
> > -- disable all HDP interrupts at unbind
> > -- replace dp_hpd_event_setup() with dp_hpd_event_thread_start()
> > -- replace dp_hpd_event_stop() with dp_hpd_event_thread_stop()
> > -- move init_waitqueue_head(&dp->event_q) to probe()
> > -- move spin_lock_init(&dp->event_lock) to probe()
> >
> > Changes in v4:
> > -- relocate both dp_display_bind() and dp_display_unbind() to bottom of file
> >
> > Changes in v5:
> > -- cancel relocation of both dp_display_bind() and dp_display_unbind()
> >
> > Changes in v6:
> > -- move empty event q to dp_event_thread_start()
> >
> > Changes in v7:
> > -- call ktheread_stop() directly instead of dp_hpd_event_thread_stop() function
> >
> > Fixes: e91e3065a806 ("drm/msm/dp: Add DP compliance tests on Snapdragon Chipsets")
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > Reported-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_display.c | 31 ++++++++++++++++++++++++-------
> >   1 file changed, 24 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 01453db..680e500 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -113,6 +113,7 @@ struct dp_display_private {
> >          u32 hpd_state;
> >          u32 event_pndx;
> >          u32 event_gndx;
> > +       struct task_struct *ev_tsk;
> >          struct dp_event event_list[DP_EVENT_Q_MAX];
> >          spinlock_t event_lock;
> >
> > @@ -230,6 +231,8 @@ void dp_display_signal_audio_complete(struct msm_dp *dp_display)
> >          complete_all(&dp->audio_comp);
> >   }
> >
> > +static int dp_hpd_event_thread_start(struct dp_display_private *dp_priv);
> > +
> >   static int dp_display_bind(struct device *dev, struct device *master,
> >                             void *data)
> >   {
> > @@ -269,6 +272,7 @@ static int dp_display_bind(struct device *dev, struct device *master,
> >          if (rc)
> >                  DRM_ERROR("Audio registration Dp failed\n");
> I think I asked it in v3 and didn't get an answer:
> Isn't 'goto end' missing here?
I did follow you suggestion at v3 and made changes at 
dp_hpd_event_thread_start()
> > +       rc = dp_hpd_event_thread_start(dp);
> if (rc) { DRM_ERROR(....); goto end; }
> return 0;
>
> Please.
This is at dp_display_bind(),  "end" is the next statement why goto needed?
> >   end:
> >          return rc;
> >   }
> > @@ -280,6 +284,11 @@ 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 all HPD interrupts */
> > +       dp_catalog_hpd_config_intr(dp->catalog, DP_DP_HPD_INT_MASK, false);
> > +
> > +       kthread_stop(dp->ev_tsk);
> > +
> >          dp_power_client_deinit(dp->power);
> >          dp_aux_unregister(dp->aux);
> >          priv->dp[dp->id] = NULL;
> > @@ -1054,7 +1063,7 @@ 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),
> > @@ -1132,12 +1141,19 @@ static int hpd_event_thread(void *data)
> >          return 0;
> >   }
> >
> > -static void dp_hpd_event_setup(struct dp_display_private *dp_priv)
> > +static int dp_hpd_event_thread_start(struct dp_display_private *dp_priv)
> >   {
> > -       init_waitqueue_head(&dp_priv->event_q);
> > -       spin_lock_init(&dp_priv->event_lock);
> > +       /* set event q to empty */
> > +       dp_priv->event_gndx = 0;
> > +       dp_priv->event_pndx = 0;
> > +
> > +       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");
> > +               return PTR_ERR(dp_priv->ev_tsk);
> > +       }
> >
> > -       kthread_run(hpd_event_thread, dp_priv, "dp_hpd_handler");
> > +       return 0;
> >   }
> >
> >   static irqreturn_t dp_display_irq_handler(int irq, void *dev_id)
> > @@ -1266,7 +1282,10 @@ static int dp_display_probe(struct platform_device *pdev)
> >                  return -EPROBE_DEFER;
> >          }
> >
> > +       /* setup event q */
> >          mutex_init(&dp->event_mutex);
> > +       init_waitqueue_head(&dp->event_q);
> > +       spin_lock_init(&dp->event_lock);
> >
> >          /* Store DP audio handle inside DP display */
> >          dp->dp_display.dp_audio = dp->audio;
> > @@ -1441,8 +1460,6 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
> >
> >          dp = container_of(dp_display, struct dp_display_private, dp_display);
> >
> > -       dp_hpd_event_setup(dp);
> > -
> >          dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
> >   }
> >
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project