Date:   Sat, 16 Apr 2022 02:40:30 +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 v8] drm/msm/dp: stop event kernel thread when DP unbind

On Sat, 16 Apr 2022 at 02:36, 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
>
> Changes in v8:
> -- return error immediately if audio registration failed.
>
> 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 | 35 +++++++++++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 01453db..590f90b 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)
>  {
> @@ -266,9 +269,12 @@ static int dp_display_bind(struct device *dev, struct device *master,
>         }
>
>         rc = dp_register_audio_driver(dev, dp->audio);
> -       if (rc)
> +       if (rc) {
>                 DRM_ERROR("Audio registration Dp failed\n");
> +               goto end;
> +       }
>
> +       rc = dp_hpd_event_thread_start(dp);

At least a DRM_ERROR is missing here. And yes, I'd ask again for a
goto/return 0;

>  end:
>         return rc;
>  }
> @@ -280,6 +286,11 @@ 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 +1065,7 @@ 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 +1143,19 @@ 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 +1284,10 @@ 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 +1462,6 @@ 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

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