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In-Reply-To: <febc4aaf-c36c-b683-d1c5-403279bd980a@quicinc.com>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Mon, 25 Sep 2023 12:06:34 +0300
Message-ID: <CAA8EJprcKwGRjsORCMRObjd5XvF2CQMtV41OM82EgHfwBYZQNQ@mail.gmail.com>
Subject: Re: [PATCH v3 4/7] drm/msm/dp: incorporate pm_runtime framework into
 DP driver
To:     Kuogee Hsieh <quic_khsieh@quicinc.com>
Cc:     dri-devel@lists.freedesktop.org, robdclark@gmail.com,
        sean@poorly.run, swboyd@chromium.org, dianders@chromium.org,
        vkoul@kernel.org, daniel@ffwll.ch, airlied@gmail.com,
        agross@kernel.org, andersson@kernel.org, quic_abhinavk@quicinc.com,
        quic_jesszhan@quicinc.com, quic_sbillaka@quicinc.com,
        marijn.suijten@somainline.org, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, 21 Sept 2023 at 01:46, Kuogee Hsieh <quic_khsieh@quicinc.com> wrote:
>
>
> On 9/15/2023 6:07 PM, Dmitry Baryshkov wrote:
> > On Sat, 16 Sept 2023 at 00:38, Kuogee Hsieh <quic_khsieh@quicinc.com> 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@quicinc.com>
> >> ---
> >>   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?

Please excuse me, it took a while to check the docs. Indeed, you were
right. For atomic drivers corresponding encoder helper calls are
required to be inverse pairs. Thus bridge calls should also be an
inverse of each other.

>
> > 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
> >>
> >


-- 
With best wishes
Dmitry