Re: [PATCH v6 4/9] media: mtk-mdp: don't pm_run_time_get/put for master comp in clock_on

[Enric Balletbo Serra]

Hi Eizan,

Thank you for your patch.

Missatge de Eizan Miyamoto <eizan@xxxxxxxxxxxx> del dia dl., 2 d’ag.
2021 a les 14:13:

>
> The original intent of commit 86698b9505bbc ("media: mtk-mdp: convert
> mtk_mdp_dev.comp array to list") was to create a list to track all the
> MDP components that needed to have their clocks enabled/disabled when
> calling mtk_mdp_comp_clock_on/off. However, there was a bug inside
> mtk_mdp_register_component where the args to a call to list_add were
> swapped. The result is that only one component was added to
> mtk_mdp_dev.comp_list because comp_list was instead being
> repeatedly added to the single element lists headed by each
> mtk_mdp_comp.
>
> The order of the args to list_add in mtk_mdp_register_component was
> fixed in https://patchwork.kernel.org/patch/11742895/ (Fix Null pointer
> dereference when calling list_add).
>
> Then, as a result of https://patchwork.kernel.org/patch/11530769/
> (mtk-mdp: use pm_runtime in MDP component driver) if all the components
> are added to the component list, the mdp "master" / rdma0 component
> ends up having pm_runtime_get_sync() called on it twice recursively:
>
>     rpm_resume+0x694/0x8f8
>     __pm_runtime_resume+0x7c/0xa0 ***NOTE***
>     mtk_mdp_comp_clock_on+0x48/0x104 [mtk_mdp]
>     mtk_mdp_pm_resume+0x2c/0x44 [mtk_mdp]
>     pm_generic_runtime_resume+0x34/0x48
>     __genpd_runtime_resume+0x6c/0x80
>     genpd_runtime_resume+0x104/0x1ac
>     __rpm_callback+0x120/0x238
>     rpm_callback+0x34/0x8c
>     rpm_resume+0x7a0/0x8f8
>     __pm_runtime_resume+0x7c/0xa0 ***NOTE***
>     mtk_mdp_m2m_start_streaming+0x2c/0x3c [mtk_mdp]
>
> (The calls to pm_runtime_get_sync are inlined and correspond to the
> calls to __pm_runtime_resume). It is not correct to have
> pm_runtime_get_sync called recursively and the second call will block
> indefinitely.
>
> As a result of all that, this change factors mtk_mdp_comp_clock_on/off
> into mtk_mdp_comp_power_on/off and moves the calls to
> pm_runtime_get/put into the power_on/off functions.
>
> This change then special-cases the master/rdma0 MDP component and does
> these things:
> - the master/rdma0 component is not added to mtk_mdp_dev.comp_list
> - the master/rdma0 component has its clocks (*but not power*) toggled
>   by mtk_mpd_comp_clock_on/off inside mtk_mdp_clock_on/off.
> - the other components have their clocks *and* power toggled with
>   mtk_mdp_comp_power_on/off.
>
> This change introduces the assumption that mtk_mdp_pm_resume will
> always be called though a callback from pm_runtime_get_sync made on the
> master / rdma0 component.
>
> Signed-off-by: Eizan Miyamoto <eizan@xxxxxxxxxxxx>
> ---
>
> (no changes since v1)
>
>  drivers/media/platform/mtk-mdp/mtk_mdp_comp.c | 57 ++++++++++++++---
>  drivers/media/platform/mtk-mdp/mtk_mdp_comp.h |  5 +-
>  drivers/media/platform/mtk-mdp/mtk_mdp_core.c | 62 ++++++++++++++-----
>  3 files changed, 98 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> index 472c261b01e8..7b6c8a3f3455 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> @@ -51,9 +51,9 @@ static const struct of_device_id mtk_mdp_comp_driver_dt_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, mtk_mdp_comp_driver_dt_match);
>
> -int mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
> +int mtk_mdp_comp_power_on(struct mtk_mdp_comp *comp)
>  {
> -       int i, err, status;
> +       int status, err;
>
>         if (comp->larb_dev) {
>                 err = mtk_smi_larb_get(comp->larb_dev);
> @@ -63,12 +63,54 @@ int mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
>
>         err = pm_runtime_get_sync(comp->dev);
>         if (err < 0) {
> -               dev_err(comp->dev,
> -                       "failed to runtime get, err %d.\n",
> -                       err);
> +               dev_err(comp->dev, "failed to runtime get, err %d.\n", err);
>                 return err;
>         }
>
> +       err = mtk_mdp_comp_clock_on(comp);
> +       if (err) {
> +               dev_err(comp->dev, "failed to turn on clock. err=%d", err);
> +               status = err;
> +               goto err_mtk_mdp_comp_clock_on;
> +       }
> +
> +       return 0;
> +
> +err_mtk_mdp_comp_clock_on:
> +       err = pm_runtime_put_sync(comp->dev);
> +       if (err)
> +               dev_err(comp->dev, "failed to runtime put in cleanup. err=%d", err);
> +
> +       return status;
> +}
> +
> +int mtk_mdp_comp_power_off(struct mtk_mdp_comp *comp)
> +{
> +       int status, err;
> +
> +       mtk_mdp_comp_clock_off(comp);
> +
> +       err = pm_runtime_put_sync(comp->dev);
> +       if (err < 0) {
> +               dev_err(comp->dev, "failed to runtime put, err %d.\n", err);
> +               status = err;
> +               goto err_pm_runtime_put_sync;
> +       }
> +
> +       return 0;
> +
> +err_pm_runtime_put_sync:
> +       err = mtk_mdp_comp_clock_on(comp);
> +       if (err)
> +               dev_err(comp->dev, "failed to turn on clock in cleanup. err=%d", err);
> +
> +       return status;
> +}
> +
> +int mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
> +{
> +       int i, err, status;
> +
>         for (i = 0; i < ARRAY_SIZE(comp->clk); i++) {
>                 if (IS_ERR(comp->clk[i]))
>                         continue;
> @@ -94,7 +136,8 @@ int mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp)
>         return status;
>  }
>
> -int mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp)
> +
> +void mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp)
>  {
>         int i;
>
> @@ -106,8 +149,6 @@ int mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp)
>
>         if (comp->larb_dev)
>                 mtk_smi_larb_put(comp->larb_dev);
> -
> -       return pm_runtime_put_sync(comp->dev);
>  }
>
>  static int mtk_mdp_comp_bind(struct device *dev, struct device *master, void *data)
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
> index f2e22e7e7c45..e3d6aef52869 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.h
> @@ -23,8 +23,11 @@ struct mtk_mdp_comp {
>
>  int mtk_mdp_comp_init(struct mtk_mdp_comp *comp, struct device *dev);
>
> +int mtk_mdp_comp_power_on(struct mtk_mdp_comp *comp);
> +int mtk_mdp_comp_power_off(struct mtk_mdp_comp *comp);
> +
>  int mtk_mdp_comp_clock_on(struct mtk_mdp_comp *comp);
> -int mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp);
> +void mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp);
>
>  extern struct platform_driver mtk_mdp_component_driver;
>
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> index 714154450981..a72a9ba41ea6 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> @@ -57,29 +57,64 @@ static int mtk_mdp_clock_on(struct mtk_mdp_dev *mdp)
>         struct device *dev = &mdp->pdev->dev;
>         int err;
>
> +       /*
> +        * The master / rdma0 component will have pm_runtime_get_sync called
> +        * on it through mtk_mdp_m2m_start_streaming, making it unnecessary to
> +        * have mtk_mdp_comp_power_on called on it.
> +        */
> +       err = mtk_mdp_comp_clock_on(&mdp->comp_self);
> +       if (err)
> +               return err;
> +
>         list_for_each_entry(comp_node, &mdp->comp_list, node) {
> -               err = mtk_mdp_comp_clock_on(comp_node);
> +               err = mtk_mdp_comp_power_on(comp_node);
>                 if (err) {
>                         status = err;
> -                       goto err_mtk_mdp_comp_clock_on;
> +                       goto err_mtk_mdp_comp_power_on;
>                 }
>         }
>
>         return 0;
>
> -err_mtk_mdp_comp_clock_on:
> -       list_for_each_entry_continue_reverse(comp_node, &mdp->comp_list, node)
> -               mtk_mdp_comp_clock_off(comp_node);
> -
> +err_mtk_mdp_comp_power_on:
> +       list_for_each_entry_continue_reverse(comp_node, &mdp->comp_list, node) {
> +               err = mtk_mdp_comp_power_off(comp_node);
> +               if (err)
> +                       dev_err(&mdp->pdev->dev, "failed to power off after error. err=%d", err);
> +       }
>         return status;
>  }
>
> -static void mtk_mdp_clock_off(struct mtk_mdp_dev *mdp)
> +static int mtk_mdp_clock_off(struct mtk_mdp_dev *mdp)
>  {
>         struct mtk_mdp_comp *comp_node;
> +       int status, err;
> +
> +       list_for_each_entry(comp_node, &mdp->comp_list, node) {
> +               err = mtk_mdp_comp_power_off(comp_node);
> +               if (err) {
> +                       status = err;
> +                       goto err_mtk_mdp_comp_power_off;
> +               }
> +       }
>
> -       list_for_each_entry(comp_node, &mdp->comp_list, node)
> -               mtk_mdp_comp_clock_off(comp_node);
> +       /*
> +        * The master / rdma0 component will have pm_runtime_put called
> +        * on it through mtk_mdp_m2m_stop_streaming, making it unnecessary to
> +        * have mtk_mdp_comp_power_off called on it.
> +        */
> +       mtk_mdp_comp_clock_off(&mdp->comp_self);
> +
> +       return 0;
> +
> +err_mtk_mdp_comp_power_off:
> +       list_for_each_entry_continue_reverse(comp_node, &mdp->comp_list, node) {
> +               err = mtk_mdp_comp_power_on(comp_node);
> +               if (err)
> +                       dev_err(&mdp->pdev->dev, "failed to power on after error. err=%d", err);
> +       }
> +
> +       return status;
>  }
>
>  static void mtk_mdp_wdt_worker(struct work_struct *work)
> @@ -118,8 +153,6 @@ static int mtk_mdp_master_bind(struct device *dev)
>         int status;
>         struct mtk_mdp_dev *mdp = dev_get_drvdata(dev);
>
> -       mtk_mdp_register_component(mdp, &mdp->comp_self);
> -
>         status = component_bind_all(dev, mdp);
>         if (status) {
>                 dev_err(dev, "Failed to bind all components: %d\n", status);
> @@ -140,8 +173,6 @@ static int mtk_mdp_master_bind(struct device *dev)
>         component_unbind_all(dev, mdp);
>
>  err_component_bind_all:
> -       mtk_mdp_unregister_component(mdp, &mdp->comp_self);
> -
>         return status;
>  }
>
> @@ -152,7 +183,6 @@ static void mtk_mdp_master_unbind(struct device *dev)
>         pm_runtime_disable(dev);
>         mtk_mdp_unregister_m2m_device(mdp);
>         component_unbind_all(dev, mdp);
> -       mtk_mdp_unregister_component(mdp, &mdp->comp_self);
>  }
>
>  static const struct component_master_ops mtk_mdp_com_ops = {
> @@ -337,9 +367,7 @@ static int __maybe_unused mtk_mdp_pm_suspend(struct device *dev)
>  {
>         struct mtk_mdp_dev *mdp = dev_get_drvdata(dev);
>
> -       mtk_mdp_clock_off(mdp);
> -
> -       return 0;
> +       return mtk_mdp_clock_off(mdp);
>  }
>
>  static int __maybe_unused mtk_mdp_pm_resume(struct device *dev)
> --
> 2.32.0.554.ge1b32706d8-goog
>