Re: [PATCH v1 2/5] drm/msm/dp: incorporate pm_runtime framework into DP driver

[Kuogee Hsieh]

On 7/7/2023 5:04 PM, Dmitry Baryshkov wrote:
> On 08/07/2023 02:52, Kuogee Hsieh wrote:
> > Incorporating pm runtime framework into DP driver so that power
> > and clock resource handling can be centralized allowing easier
> > control of these resources in preparation of registering aux bus
> > uring probe.
> >
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_aux.c     |  3 ++
> >   drivers/gpu/drm/msm/dp/dp_display.c | 75 
> > +++++++++++++++++++++++++++++--------
> >   2 files changed, 63 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c 
> > b/drivers/gpu/drm/msm/dp/dp_aux.c
> > index 8e3b677..c592064 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_aux.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_aux.c
> > @@ -291,6 +291,7 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux 
> > *dp_aux,
> >           return -EINVAL;
> >       }
> >   +    pm_runtime_get_sync(dp_aux->dev);
>
> Let me quote the function's documentation:
> Consider using pm_runtime_resume_and_get() instead of it, especially 
> if its return value is checked by the caller, as this is likely to 
> result in cleaner code.
>
> So two notes concerning the whole patch:
> - error checking is missing
> - please use pm_runtime_resume_and_get() instead.
>
> >       mutex_lock(&aux->mutex);
> >       if (!aux->initted) {
> >           ret = -EIO;
> > @@ -364,6 +365,8 @@ 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);
> >         return ret;
> >   }
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
> > b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 76f1395..2c5706a 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -309,6 +309,10 @@ static int dp_display_bind(struct device *dev, 
> > struct device *master,
> >           goto end;
> >       }
> >   +    pm_runtime_enable(dev);
>
> devm_pm_runtime_enable() removes need for a cleanup.
>
> > +    pm_runtime_set_autosuspend_delay(dev, 1000);
> > +    pm_runtime_use_autosuspend(dev);
>
> Why do you want to use autosuspend here?
>
> > +
> >       return 0;
> >   end:
> >       return rc;
> > @@ -320,9 +324,8 @@ 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);
> > +    pm_runtime_dont_use_autosuspend(dev);
> > +    pm_runtime_disable(dev);
> >         kthread_stop(dp->ev_tsk);
> >   @@ -466,10 +469,12 @@ static void dp_display_host_init(struct 
> > dp_display_private *dp)
> >           dp->dp_display.connector_type, dp->core_initialized,
> >           dp->phy_initialized);
> >   -    dp_power_init(dp->power);
> > -    dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
> > -    dp_aux_init(dp->aux);
> > -    dp->core_initialized = true;
> > +    if (!dp->core_initialized) {
> > +        dp_power_init(dp->power);
> > +        dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
> > +        dp_aux_init(dp->aux);
> > +        dp->core_initialized = true;
> > +    }
>
> Is this relevant to PM runtime? I don't think so.
>
> >   }
> >     static void dp_display_host_deinit(struct dp_display_private *dp)
> > @@ -478,10 +483,12 @@ static void dp_display_host_deinit(struct 
> > dp_display_private *dp)
> >           dp->dp_display.connector_type, dp->core_initialized,
> >           dp->phy_initialized);
> >   -    dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
> > -    dp_aux_deinit(dp->aux);
> > -    dp_power_deinit(dp->power);
> > -    dp->core_initialized = false;
> > +    if (dp->core_initialized) {
> > +        dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
> > +        dp_aux_deinit(dp->aux);
> > +        dp_power_deinit(dp->power);
> > +        dp->core_initialized = false;
> > +    }
> >   }
> >     static int dp_display_usbpd_configure_cb(struct device *dev)
> > @@ -1304,6 +1311,39 @@ static int dp_display_remove(struct 
> > platform_device *pdev)
> >       dp_display_deinit_sub_modules(dp);
> >         platform_set_drvdata(pdev, NULL);
> > +    pm_runtime_put_sync_suspend(&pdev->dev);
> > +
> > +    return 0;
> > +}
> > +
> > +static int dp_pm_runtime_suspend(struct device *dev)
> > +{
> > +    struct platform_device *pdev = to_platform_device(dev);
> > +    struct msm_dp *dp_display = platform_get_drvdata(pdev);
> > +    struct dp_display_private *dp;
> > +
> > +    dp = container_of(dp_display, struct dp_display_private, 
> > dp_display);
> > +
> > +    dp_display_host_phy_exit(dp);
> > +    dp_catalog_ctrl_hpd_enable(dp->catalog);
>
> What? NO!
>
> > +    dp_display_host_deinit(dp);
> > +
> > +    return 0;
> > +}
> > +
> > +static int dp_pm_runtime_resume(struct device *dev)
> > +{
> > +    struct platform_device *pdev = to_platform_device(dev);
> > +    struct msm_dp *dp_display = platform_get_drvdata(pdev);
> > +    struct dp_display_private *dp;
> > +
> > +    dp = container_of(dp_display, struct dp_display_private, 
> > dp_display);
> > +
> > +    dp_display_host_init(dp);
> > +    if (dp_display->is_edp) {
> > +        dp_catalog_ctrl_hpd_enable(dp->catalog);
> > +        dp_display_host_phy_init(dp);
> > +    }
> >         return 0;
> >   }
> > @@ -1409,6 +1449,7 @@ 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,
>
> With the runtime PM in place, can we change suspend/resume to use 
> pm_runtime_force_suspend() and pm_runtime_force_resume() ?
>
>
> >   };
> > @@ -1493,10 +1534,6 @@ 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);
>
> Are you going to populate the AUX bus (which can cause AUX bus access) 
> without waking up the device?

no,  pm_runtime_get_sync() will be called inside 
generic_edp_panel_probe() which will trigger dp_pm_runtime_resume() be 
called to wake up device (initialize dp host) before retrieve

panel_id from edp panel through aux bus.

> > -
> >           /*
> >            * The code below assumes that the panel will finish probing
> >            * by the time devm_of_dp_aux_populate_ep_devices() returns.
> > @@ -1604,6 +1641,7 @@ void dp_bridge_atomic_enable(struct drm_bridge 
> > *drm_bridge,
> >           dp_hpd_plug_handle(dp_display, 0);
>
> Nearly the same question. Resume device before accessing registers.
>
> > mutex_lock(&dp_display->event_mutex);
> > +    pm_runtime_get_sync(&dp_display->pdev->dev);
> >         state = dp_display->hpd_state;
> >       if (state != ST_DISPLAY_OFF && state != ST_MAINLINK_READY) {
> > @@ -1684,6 +1722,8 @@ 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);
> >       mutex_unlock(&dp_display->event_mutex);
> >   }
> >   @@ -1723,6 +1763,8 @@ 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);
> > +    pm_runtime_get_sync(&dp->pdev->dev);
> > +
> >       dp_catalog_ctrl_hpd_enable(dp->catalog);
> >         /* enable HDP interrupts */
> > @@ -1744,6 +1786,9 @@ 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);
> >   }