Re: [PATCH v2] drm/msm/dp: enhance both connect and disconnect pending_timeout handle

[Stephen Boyd <swboyd@chromium.org>]

The subject is still misleading. It is fixing something. It may be
enhancing it as well but it is clearly fixing it first.

Quoting Kuogee Hsieh (2022-04-06 14:28:13)
> dp_hpd_plug_handle() is responsible for setting up main link and send
> uevent to notify user space framework to start video stream. Similarly,
> dp_hdp_unplug_handle is responsible to send uevent to notify user space
> framework to stop video stream and then tear down main link.
> However there are rare cases, such as in the middle of system suspending,
> that uevent could not be delivered to user space framework. Therefore
> some kind of recover mechanism armed by timer need to be in place in the
> case of user space framework does not respond to uevent.
>
> This patch have both dp_conenct_pending_timeout and
> dp_disconnect_pending_timeout are used to stop video stream and tear down
> main link and eventually restore DP driver state to known default
> DISCONNECTED state in the case of timer fired due to framework does not
> respond to uevent so that DP driver can recover itself gracefully at next
> dongle unplug followed by plugin event.
>
> Changes in v2:
> -- replace dp_display_usbpd_disconnect_cb with dp_display_notify_disconnect

I'd prefer this part to be a different patch. It can come after the fix
to ease backporting.

Also, is there any response to Dmitry's question yet? I haven't seen
anything.

> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> index 2433edb..ffafe17 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.h
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> @@ -22,6 +22,7 @@ struct dp_ctrl {
>  int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl);
>  int dp_ctrl_on_stream(struct dp_ctrl *dp_ctrl);
>  int dp_ctrl_off_link_stream(struct dp_ctrl *dp_ctrl);
> +int dp_ctrl_off_link(struct dp_ctrl *dp_ctrl);
>  int dp_ctrl_off(struct dp_ctrl *dp_ctrl);
>  void dp_ctrl_push_idle(struct dp_ctrl *dp_ctrl);
>  void dp_ctrl_isr(struct dp_ctrl *dp_ctrl);
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 178b774..a6200a5 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -451,11 +451,14 @@ static int dp_display_usbpd_configure_cb(struct device *dev)
>
>  static int dp_display_usbpd_disconnect_cb(struct device *dev)

We shouldn't need to keep around an empty function.

>  {
> +       return 0;
> +}
> +
> +static void dp_display_notify_disconnect(struct device *dev)
> +{
>         struct dp_display_private *dp = dev_get_dp_display_private(dev);
>
>         dp_add_event(dp, EV_USER_NOTIFICATION, false, 0);
> -
> -       return 0;
>  }
>
>  static void dp_display_handle_video_request(struct dp_display_private *dp)
> @@ -593,10 +596,16 @@ static int dp_connect_pending_timeout(struct dp_display_private *dp, u32 data)
>
>         mutex_lock(&dp->event_mutex);
>
> +       /*
> +        * main link had been setup but video is not ready yet
> +        * only tear down main link
> +        */
>         state = dp->hpd_state;
>         if (state == ST_CONNECT_PENDING) {
> -               dp->hpd_state = ST_CONNECTED;
>                 DRM_DEBUG_DP("type=%d\n", dp->dp_display.connector_type);
> +               dp_ctrl_off_link(dp->ctrl);
> +               dp_display_host_phy_exit(dp);
> +               dp->hpd_state = ST_DISCONNECTED;
>         }
>
>         mutex_unlock(&dp->event_mutex);
> @@ -645,6 +654,7 @@ static int dp_hpd_unplug_handle(struct dp_display_private *dp, u32 data)
>                 if (dp->link->sink_count == 0) {
>                         dp_display_host_phy_exit(dp);
>                 }
> +               dp_display_notify_disconnect(&dp->pdev->dev);
>                 mutex_unlock(&dp->event_mutex);
>                 return 0;
>         }
> @@ -661,19 +671,22 @@ static int dp_hpd_unplug_handle(struct dp_display_private *dp, u32 data)
>                 return 0;
>         }
>
> -       dp->hpd_state = ST_DISCONNECT_PENDING;
> -
>         /* disable HPD plug interrupts */
>         dp_catalog_hpd_config_intr(dp->catalog, DP_DP_HPD_PLUG_INT_MASK, false);
>
>         /*
>          * We don't need separate work for disconnect as
>          * connect/attention interrupts are disabled
> -        */
> -       dp_display_usbpd_disconnect_cb(&dp->pdev->dev);
> +       */

This comment end is wrong. It should be unchanged.

> +       dp_display_notify_disconnect(&dp->pdev->dev);
>
> -       /* start sentinel checking in case of missing uevent */
> -       dp_add_event(dp, EV_DISCONNECT_PENDING_TIMEOUT, 0, DP_TIMEOUT_5_SECOND);
> +       if (state == ST_DISPLAY_OFF) {
> +               dp->hpd_state = ST_DISCONNECTED;
> +       } else {
> +               /* start sentinel checking in case of missing uevent */
> +               dp_add_event(dp, EV_DISCONNECT_PENDING_TIMEOUT, 0, DP_TIMEOUT_5_SECOND);
> +               dp->hpd_state = ST_DISCONNECT_PENDING;
> +       }
>
>         /* signal the disconnect event early to ensure proper teardown */
>         dp_display_handle_plugged_change(&dp->dp_display, false);
> @@ -695,10 +708,16 @@ static int dp_disconnect_pending_timeout(struct dp_display_private *dp, u32 data
>
>         mutex_lock(&dp->event_mutex);
>
> +       /*
> +        * main link had been set up and video is ready
> +        * tear down main link, video stream and phy
> +        */
>         state =  dp->hpd_state;
>         if (state == ST_DISCONNECT_PENDING) {
> -               dp->hpd_state = ST_DISCONNECTED;
>                 DRM_DEBUG_DP("type=%d\n", dp->dp_display.connector_type);
> +               dp_ctrl_off(dp->ctrl);
> +               dp_display_host_phy_exit(dp);
> +               dp->hpd_state = ST_DISCONNECTED;
>         }
>
>         mutex_unlock(&dp->event_mutex);