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

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Message-ID: <CAA8EJpr54Wrjv9+7H97n9i+2zPX6qNH3Vqf-92CRtayhQexhYQ@mail.gmail.com>
Date:   Sat, 16 Apr 2022 02:27:36 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org,
        quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7] drm/msm/dp: stop event kernel thread when DP unbind

On Sat, 16 Apr 2022 at 02:10, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>
>
> On 4/15/2022 3:48 PM, Dmitry Baryshkov wrote:
> > On Sat, 16 Apr 2022 at 01:34, Kuogee Hsieh <quic_khsieh@...cinc.com> 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@...cinc.com>
> >> Reported-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> >> ---
> >>   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()

I'm asking about this place. Should we return an immediate error if
audio registration has failed or not?

> >> +       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?

To be explicit that this is a fatal error. Compare this to my question
regarding the audio registration failure.

> >>   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
> >>
> >



-- 
With best wishes
Dmitry