Re: [PATCH v3 4/7] drm/msm/dp: incorporate pm_runtime framework into DP driver

[Kuogee Hsieh]

On 9/15/2023 6:07 PM, Dmitry Baryshkov wrote:
> On Sat, 16 Sept 2023 at 00:38, Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> wrote:
> > Currently DP driver is executed independent of PM runtime framework.
> > This lead DP driver incompatible with others. Incorporating pm runtime
> Why is it incompatible? Which others are mentioned here?
>
> > framework into DP driver so that both power and clocks to enable/disable
> > host controller fits with PM runtime mechanism. Once pm runtime framework
> > is incorporated into DP driver, wake up device from power up path is not
> > necessary. Hence remove it. Both EV_POWER_PM_GET and EV_POWER_PM_PUT events
> > are introduced to perform pm runtime control for the HPD GPIO routing to a
> > display-connector case.
> >
> > Changes in v3:
> > -- incorporate removing pm_runtime_xx() from dp_pwer.c to this patch
> > -- use pm_runtime_resume_and_get() instead of pm_runtime_get()
> > -- error checking pm_runtime_resume_and_get() return value
> > -- add EV_POWER_PM_GET and PM_EV_POWER_PUT to handle HPD_GPIO case
> Previous changelog?
>
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_aux.c     |   5 ++
> >   drivers/gpu/drm/msm/dp/dp_display.c | 114 +++++++++++++++++++++++++++---------
> >   drivers/gpu/drm/msm/dp/dp_power.c   |   9 ---
> >   3 files changed, 90 insertions(+), 38 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c
> > index 8e3b677..8fa93c5 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_aux.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
> > @@ -291,6 +291,9 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
> >                  return -EINVAL;
> >          }
> >
> > +       if (pm_runtime_resume_and_get(dp_aux->dev))
> > +               return  -EINVAL;
> Please propagate error values instead of reinventing them.
>
> > +
> >          mutex_lock(&aux->mutex);
> >          if (!aux->initted) {
> >                  ret = -EIO;
> > @@ -364,6 +367,8 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
> >
> >   exit:
> >          mutex_unlock(&aux->mutex);
> > +       pm_runtime_mark_last_busy(dp_aux->dev);
> > +       pm_runtime_put_autosuspend(dp_aux->dev);
> What is the reason for using autosuspend? Such design decisions should
> be described in the commit message.
>
> >          return ret;
> >   }
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 59f9d85..e7af7f7 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -60,6 +60,8 @@ enum {
> >          EV_IRQ_HPD_INT,
> >          EV_HPD_UNPLUG_INT,
> >          EV_USER_NOTIFICATION,
> > +       EV_POWER_PM_GET,
> > +       EV_POWER_PM_PUT,
> >   };
> >
> >   #define EVENT_TIMEOUT  (HZ/10) /* 100ms */
> > @@ -276,13 +278,6 @@ static int dp_display_bind(struct device *dev, struct device *master,
> >          dp->dp_display.drm_dev = drm;
> >          priv->dp[dp->id] = &dp->dp_display;
> >
> > -       rc = dp->parser->parse(dp->parser);
> > -       if (rc) {
> > -               DRM_ERROR("device tree parsing failed\n");
> > -               goto end;
> > -       }
> > -
> > -
> >          dp->drm_dev = drm;
> >          dp->aux->drm_dev = drm;
> >          rc = dp_aux_register(dp->aux);
> > @@ -291,12 +286,6 @@ static int dp_display_bind(struct device *dev, struct device *master,
> >                  goto end;
> >          }
> >
> > -       rc = dp_power_client_init(dp->power);
> > -       if (rc) {
> > -               DRM_ERROR("Power client create failed\n");
> > -               goto end;
> > -       }
> > -
> >          rc = dp_register_audio_driver(dev, dp->audio);
> >          if (rc) {
> >                  DRM_ERROR("Audio registration Dp failed\n");
> > @@ -320,10 +309,6 @@ static void dp_display_unbind(struct device *dev, struct device *master,
> >          struct dp_display_private *dp = dev_get_dp_display_private(dev);
> >          struct msm_drm_private *priv = dev_get_drvdata(master);
> >
> > -       /* disable all HPD interrupts */
> > -       if (dp->core_initialized)
> > -               dp_catalog_hpd_config_intr(dp->catalog, DP_DP_HPD_INT_MASK, false);
> > -
> >          kthread_stop(dp->ev_tsk);
> >
> >          of_dp_aux_depopulate_bus(dp->aux);
> > @@ -467,6 +452,18 @@ static void dp_display_host_deinit(struct dp_display_private *dp)
> >          dp->core_initialized = false;
> >   }
> >
> > +static void dp_display_pm_get(struct dp_display_private *dp)
> > +{
> > +       if (pm_runtime_resume_and_get(&dp->pdev->dev))
> > +               DRM_ERROR("failed to start power\n");
> > +}
> Huge NAK here. This means that the error is completely ignored (other
> than being dumped to the log). This is a short path to Sync error and
> other kinds of reboot.
>
> > +
> > +static void dp_display_pm_put(struct dp_display_private *dp)
> > +{
> > +       pm_runtime_mark_last_busy(&dp->pdev->dev);
> > +       pm_runtime_put_autosuspend(&dp->pdev->dev);
> > +}
> > +
> >   static int dp_display_usbpd_configure_cb(struct device *dev)
> >   {
> >          struct dp_display_private *dp = dev_get_dp_display_private(dev);
> > @@ -1096,7 +1093,6 @@ static int hpd_event_thread(void *data)
> >
> >                  switch (todo->event_id) {
> >                  case EV_HPD_INIT_SETUP:
> > -                       dp_display_host_init(dp_priv);
> >                          break;
> >                  case EV_HPD_PLUG_INT:
> >                          dp_hpd_plug_handle(dp_priv, todo->data);
> > @@ -1111,6 +1107,12 @@ static int hpd_event_thread(void *data)
> >                          dp_display_send_hpd_notification(dp_priv,
> >                                                  todo->data);
> >                          break;
> > +               case EV_POWER_PM_GET:
> > +                       dp_display_pm_get(dp_priv);
> > +                       break;
> > +               case EV_POWER_PM_PUT:
> > +                       dp_display_pm_put(dp_priv);
> > +                       break;
> No. runtime_get / runtime_put are not HPD events. They should be
> executed directly from the place where the drivers needs the device to
> be powered up.
>
> >                  default:
> >                          break;
> >                  }
> > @@ -1251,6 +1253,18 @@ static int dp_display_probe(struct platform_device *pdev)
> >                  return -EPROBE_DEFER;
> >          }
> >
> > +       rc = dp->parser->parse(dp->parser);
> > +       if (rc) {
> > +               DRM_ERROR("device tree parsing failed\n");
> > +               return -EPROBE_DEFER;
> > +       }
> > +
> > +       rc = dp_power_client_init(dp->power);
> > +       if (rc) {
> > +               DRM_ERROR("Power client create failed\n");
> > +               return -EPROBE_DEFER;
> > +       }
> Why? This moves resource allocation to the probe function, which is
> irrelevant to the pm_runtime code. If this is required, you can move
> these changes to a separate patch.
>
> > +
> >          /* setup event q */
> >          mutex_init(&dp->event_mutex);
> >          init_waitqueue_head(&dp->event_q);
> > @@ -1263,6 +1277,10 @@ static int dp_display_probe(struct platform_device *pdev)
> >
> >          platform_set_drvdata(pdev, &dp->dp_display);
> >
> > +       devm_pm_runtime_enable(&pdev->dev);
> error code handling?
>
> > +       pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
> > +       pm_runtime_use_autosuspend(&pdev->dev);
> > +
> >          rc = dp_display_request_irq(dp);
> >          if (rc)
> >                  return rc;
> > @@ -1285,6 +1303,36 @@ static int dp_display_remove(struct platform_device *pdev)
> >
> >          platform_set_drvdata(pdev, NULL);
> >
> > +       pm_runtime_put_sync_suspend(&pdev->dev);
> Why? Who is holding the pm count here?
>
> > +       pm_runtime_dont_use_autosuspend(&pdev->dev);
> > +       pm_runtime_disable(&pdev->dev);
> Why do you need _disable if you have a devm_pm_runtime_enable()? Not
> to mention that pm_runtime_disable_action() already has a call to
> pm_runtime_dont_use_autosuspend()
>
> > +
> > +       return 0;
> > +}
> > +
> > +static int dp_pm_runtime_suspend(struct device *dev)
> > +{
> > +       struct dp_display_private *dp = dev_get_dp_display_private(dev);
> > +
> > +       if (dp->dp_display.is_edp) {
> > +               dp_display_host_phy_exit(dp);
> > +               dp_catalog_ctrl_hpd_disable(dp->catalog);
> > +       }
> > +       dp_display_host_deinit(dp);
> > +
> > +       return 0;
> > +}
> > +
> > +static int dp_pm_runtime_resume(struct device *dev)
> > +{
> > +       struct dp_display_private *dp = dev_get_dp_display_private(dev);
> > +
> > +       dp_display_host_init(dp);
> > +       if (dp->dp_display.is_edp) {
> > +               dp_catalog_ctrl_hpd_enable(dp->catalog);
> > +               dp_display_host_phy_init(dp);
> > +       }
> > +
> >          return 0;
> >   }
> >
> > @@ -1389,6 +1437,7 @@ static int dp_pm_suspend(struct device *dev)
> >   }
> >
> >   static const struct dev_pm_ops dp_pm_ops = {
> > +       SET_RUNTIME_PM_OPS(dp_pm_runtime_suspend, dp_pm_runtime_resume, NULL)
> >          .suspend = dp_pm_suspend,
> >          .resume =  dp_pm_resume,
> >   };
> > @@ -1473,10 +1522,6 @@ static int dp_display_get_next_bridge(struct msm_dp *dp)
> >          aux_bus = of_get_child_by_name(dev->of_node, "aux-bus");
> >
> >          if (aux_bus && dp->is_edp) {
> > -               dp_display_host_init(dp_priv);
> > -               dp_catalog_ctrl_hpd_enable(dp_priv->catalog);
> > -               dp_display_host_phy_init(dp_priv);
> > -
> >                  /*
> >                   * The code below assumes that the panel will finish probing
> >                   * by the time devm_of_dp_aux_populate_ep_devices() returns.
> > @@ -1578,6 +1623,11 @@ void dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
> >                  dp_hpd_plug_handle(dp_display, 0);
> >
> >          mutex_lock(&dp_display->event_mutex);
> > +       if (pm_runtime_resume_and_get(&dp_display->pdev->dev)) {
> > +               DRM_ERROR("failed to start power\n");
> > +               mutex_unlock(&dp_display->event_mutex);
> > +               return;
> > +       }
> >
> >          state = dp_display->hpd_state;
> >          if (state != ST_DISPLAY_OFF && state != ST_MAINLINK_READY) {
> > @@ -1658,6 +1708,8 @@ void dp_bridge_atomic_post_disable(struct drm_bridge *drm_bridge,
> >          }
> >
> >          drm_dbg_dp(dp->drm_dev, "type=%d Done\n", dp->connector_type);
> > +
> > +       pm_runtime_put_sync(&dp_display->pdev->dev);
> So, no autosuspend now?
>
> Also, I think we can get an unbalanced runtime status, as there is no
> guarantee that atomic_enable / atomic_disable will be paired. Please
> correct me if I'm wrong.

 I always assume atomic_enable / atomic_disable should be paired.
Otherwise nothing will work.
Could you please give me example what situations they are not paired?

> And also there is a possible return earlier in this function. The
> driver will leak the runtime status again.
>
> >          mutex_unlock(&dp_display->event_mutex);
> >   }
> >
> > @@ -1697,6 +1749,9 @@ void dp_bridge_hpd_enable(struct drm_bridge *bridge)
> >          struct dp_display_private *dp = container_of(dp_display, struct dp_display_private, dp_display);
> >
> >          mutex_lock(&dp->event_mutex);
> > +       if (pm_runtime_resume_and_get(&dp->pdev->dev))
> > +               DRM_ERROR("failed to start power\n");
> Return?
>
> > +
> >          dp_catalog_ctrl_hpd_enable(dp->catalog);
> >
> >          /* enable HDP interrupts */
> > @@ -1718,6 +1773,9 @@ void dp_bridge_hpd_disable(struct drm_bridge *bridge)
> >          dp_catalog_ctrl_hpd_disable(dp->catalog);
> >
> >          dp_display->internal_hpd = false;
> > +
> > +       pm_runtime_mark_last_busy(&dp->pdev->dev);
> > +       pm_runtime_put_autosuspend(&dp->pdev->dev);
> >          mutex_unlock(&dp->event_mutex);
> >   }
> >
> > @@ -1732,13 +1790,11 @@ void dp_bridge_hpd_notify(struct drm_bridge *bridge,
> >          if (dp_display->internal_hpd)
> >                  return;
> >
> > -       if (!dp->core_initialized) {
> > -               drm_dbg_dp(dp->drm_dev, "not initialized\n");
> > -               return;
> > -       }
> > -
> > -       if (!dp_display->link_ready && status == connector_status_connected)
> > +       if (!dp_display->link_ready && status == connector_status_connected) {
> > +               dp_add_event(dp, EV_POWER_PM_GET, 0, 0);
> Why? What for?
>
> >                  dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
> > -       else if (dp_display->link_ready && status == connector_status_disconnected)
> > +       } else if (dp_display->link_ready && status == connector_status_disconnected) {
> >                  dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> > +               dp_add_event(dp, EV_POWER_PM_PUT, 0, 0);
> > +       }
> >   }
> > diff --git a/drivers/gpu/drm/msm/dp/dp_power.c b/drivers/gpu/drm/msm/dp/dp_power.c
> > index 5cb84ca..ed2f62a 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_power.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_power.c
> > @@ -152,8 +152,6 @@ int dp_power_client_init(struct dp_power *dp_power)
> >
> >          power = container_of(dp_power, struct dp_power_private, dp_power);
> >
> > -       pm_runtime_enable(power->dev);
> > -
> >          return dp_power_clk_init(power);
> >   }
> >
> > @@ -162,8 +160,6 @@ void dp_power_client_deinit(struct dp_power *dp_power)
> >          struct dp_power_private *power;
> >
> >          power = container_of(dp_power, struct dp_power_private, dp_power);
> > -
> > -       pm_runtime_disable(power->dev);
> >   }
> >
> >   int dp_power_init(struct dp_power *dp_power)
> > @@ -173,11 +169,7 @@ int dp_power_init(struct dp_power *dp_power)
> >
> >          power = container_of(dp_power, struct dp_power_private, dp_power);
> >
> > -       pm_runtime_get_sync(power->dev);
> > -
> >          rc = dp_power_clk_enable(dp_power, DP_CORE_PM, true);
> > -       if (rc)
> > -               pm_runtime_put_sync(power->dev);
> >
> >          return rc;
> >   }
> > @@ -189,7 +181,6 @@ int dp_power_deinit(struct dp_power *dp_power)
> >          power = container_of(dp_power, struct dp_power_private, dp_power);
> >
> >          dp_power_clk_enable(dp_power, DP_CORE_PM, false);
> > -       pm_runtime_put_sync(power->dev);
> >          return 0;
> >   }
> >
> > --
> > 2.7.4