Re: [PATCH] remoteproc: qcom: Add NOTIFY_FATAL event type to SSR subdevice

[Mukesh Ojha <quic_mojha@xxxxxxxxxxx>]

On 5/3/2023 4:56 PM, Mukesh Ojha wrote:
> On 5/3/2023 11:51 AM, Vignesh Viswanathan wrote:
> > Currently the SSR subdevice notifies the client driver on crash of the
> > rproc from the recovery workqueue using the BEFORE_SHUTDOWN event.
> > However the client driver might be interested to know that the device
> > has crashed immediately to pause any further transactions with the
> > rproc. This calls for an event to be sent to the driver in the IRQ
> > context as soon as the rproc crashes.
> >
> > Add NOTIFY_FATAL event to SSR subdevice to atomically notify rproc has
> > crashed to the client driver.
> >
> > Validated the event in IPQ9574 and IPQ5332 by forcing the rproc to crash
> > and ensuring the registered notifier function receives the notification
> > in IRQ context.
>
> This was one of valid use case we encounter in android, We have some 
> other way of doing the same thing without core kernel change with
> something called early notifiers.
>
> https://git.codelinaro.org/clo/la/kernel/msm-5.15/-/commit/7583d24de337aa1bf7c375a7da706af9b995b9a1#a840754ebb0e24e88adbf48177e1abd0830b72d2
>
> https://git.codelinaro.org/clo/la/kernel/msm-5.15/-/commit/257de41c63a5a51a081cc7887cdaa4a46e4d1744
>
> But good to address this if possible.

Ack the idea of early notifier;
But here, atomic does not guarantees it to be atomic.

Acked-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>

-- Mukesh


> -Mukesh
> > Signed-off-by: Vignesh Viswanathan <quic_viswanat@xxxxxxxxxxx>
> > ---
> >   drivers/remoteproc/qcom_common.c      | 60 +++++++++++++++++++++++++++
> >   drivers/remoteproc/remoteproc_core.c  | 12 ++++++
> >   include/linux/remoteproc.h            |  3 ++
> >   include/linux/remoteproc/qcom_rproc.h | 17 ++++++++
> >   4 files changed, 92 insertions(+)
> >
> > diff --git a/drivers/remoteproc/qcom_common.c 
> > b/drivers/remoteproc/qcom_common.c
> > index a0d4238492e9..76542229aeb6 100644
> > --- a/drivers/remoteproc/qcom_common.c
> > +++ b/drivers/remoteproc/qcom_common.c
> > @@ -84,6 +84,7 @@ struct minidump_global_toc {
> >   struct qcom_ssr_subsystem {
> >       const char *name;
> >       struct srcu_notifier_head notifier_list;
> > +    struct atomic_notifier_head atomic_notifier_list;
> >       struct list_head list;
> >   };
> > @@ -366,6 +367,7 @@ static struct qcom_ssr_subsystem 
> > *qcom_ssr_get_subsys(const char *name)
> >       }
> >       info->name = kstrdup_const(name, GFP_KERNEL);
> >       srcu_init_notifier_head(&info->notifier_list);
> > +    ATOMIC_INIT_NOTIFIER_HEAD(&info->atomic_notifier_list);
> >       /* Add to global notification list */
> >       list_add_tail(&info->list, &qcom_ssr_subsystem_list);
> > @@ -417,6 +419,51 @@ int qcom_unregister_ssr_notifier(void *notify, 
> > struct notifier_block *nb)
> >   }
> >   EXPORT_SYMBOL_GPL(qcom_unregister_ssr_notifier);
> > +/**
> > + * qcom_register_ssr_atomic_notifier() - register SSR Atomic 
> > notification
> > + *                     handler
> > + * @name:    Subsystem's SSR name
> > + * @nb:    notifier_block to be invoked upon subsystem's state change
> > + *
> > + * This registers the @nb notifier block as part the atomic notifier
> > + * chain for a remoteproc associated with @name. The notifier block's 
> > callback
> > + * will be invoked when the remote processor crashes in atomic 
> > context before
> > + * the recovery process is queued.
> > + *
> > + * Return: a subsystem cookie on success, ERR_PTR on failure.
> > + */
> > +void *qcom_register_ssr_atomic_notifier(const char *name,
> > +                    struct notifier_block *nb)
> > +{
> > +    struct qcom_ssr_subsystem *info;
> > +
> > +    info = qcom_ssr_get_subsys(name);
> > +    if (IS_ERR(info))
> > +        return info;
> > +
> > +    atomic_notifier_chain_register(&info->atomic_notifier_list, nb);
> > +
> > +    return &info->atomic_notifier_list;
> > +}
> > +EXPORT_SYMBOL_GPL(qcom_register_ssr_atomic_notifier);
> > +
> > +/**
> > + * qcom_unregister_ssr_atomic_notifier() - unregister SSR Atomic 
> > notification
> > + *                       handler
> > + * @notify:    subsystem cookie returned from qcom_register_ssr_notifier
> > + * @nb:        notifier_block to unregister
> > + *
> > + * This function will unregister the notifier from the atomic notifier
> > + * chain.
> > + *
> > + * Return: 0 on success, %ENOENT otherwise.
> > + */
> > +int qcom_unregister_ssr_atomic_notifier(void *notify, struct 
> > notifier_block *nb)
> > +{
> > +    return atomic_notifier_chain_unregister(notify, nb);
> > +}
> > +EXPORT_SYMBOL_GPL(qcom_unregister_ssr_atomic_notifier);
> > +
> >   static int ssr_notify_prepare(struct rproc_subdev *subdev)
> >   {
> >       struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> > @@ -467,6 +514,18 @@ static void ssr_notify_unprepare(struct 
> > rproc_subdev *subdev)
> >                    QCOM_SSR_AFTER_SHUTDOWN, &data);
> >   }
> > +static void ssr_notify_crash(struct rproc_subdev *subdev)
> > +{
> > +    struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> > +    struct qcom_ssr_notify_data data = {
> > +        .name = ssr->info->name,
> > +        .crashed = true,
> > +    };
> > +
> > +    atomic_notifier_call_chain(&ssr->info->atomic_notifier_list,
> > +                   QCOM_SSR_NOTIFY_CRASH, &data);
> > +}
> > +
> >   /**
> >    * qcom_add_ssr_subdev() - register subdevice as restart 
> > notification source
> >    * @rproc:    rproc handle
> > @@ -493,6 +552,7 @@ void qcom_add_ssr_subdev(struct rproc *rproc, 
> > struct qcom_rproc_ssr *ssr,
> >       ssr->subdev.start = ssr_notify_start;
> >       ssr->subdev.stop = ssr_notify_stop;
> >       ssr->subdev.unprepare = ssr_notify_unprepare;
> > +    ssr->subdev.notify_crash = ssr_notify_crash;
> >       rproc_add_subdev(rproc, &ssr->subdev);
> >   }
> > diff --git a/drivers/remoteproc/remoteproc_core.c 
> > b/drivers/remoteproc/remoteproc_core.c
> > index 695cce218e8c..3de0ece158ea 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -1139,6 +1139,16 @@ static void rproc_unprepare_subdevices(struct 
> > rproc *rproc)
> >       }
> >   }
> > +static void rproc_notify_crash_subdevices(struct rproc *rproc)
> > +{
> > +    struct rproc_subdev *subdev;
> > +
> > +    list_for_each_entry_reverse(subdev, &rproc->subdevs, node) {
> > +        if (subdev->notify_crash)
> > +            subdev->notify_crash(subdev);
> > +    }
> > +}
> > +
> >   /**
> >    * rproc_alloc_registered_carveouts() - allocate all carveouts 
> > registered
> >    * in the list
> > @@ -2687,6 +2697,8 @@ void rproc_report_crash(struct rproc *rproc, 
> > enum rproc_crash_type type)
> >       dev_err(&rproc->dev, "crash detected in %s: type %s\n",
> >           rproc->name, rproc_crash_to_string(type));
> > +    rproc_notify_crash_subdevices(rproc);
> > +
> >       queue_work(rproc_recovery_wq, &rproc->crash_handler);
> >   }
> >   EXPORT_SYMBOL(rproc_report_crash);
> > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > index fe8978eb69f1..f3c0e0103e81 100644
> > --- a/include/linux/remoteproc.h
> > +++ b/include/linux/remoteproc.h
> > @@ -596,6 +596,8 @@ struct rproc {
> >    * @stop: stop function, called before the rproc is stopped; the 
> > @crashed
> >    *        parameter indicates if this originates from a recovery
> >    * @unprepare: unprepare function, called after the rproc has been 
> > stopped
> > + * @notify_crash: notify_crash function, called in atomic context to 
> > notify
> > + *          rproc has crashed and recovery is about to start
> >    */
> >   struct rproc_subdev {
> >       struct list_head node;
> > @@ -604,6 +606,7 @@ struct rproc_subdev {
> >       int (*start)(struct rproc_subdev *subdev);
> >       void (*stop)(struct rproc_subdev *subdev, bool crashed);
> >       void (*unprepare)(struct rproc_subdev *subdev);
> > +    void (*notify_crash)(struct rproc_subdev *subdev);
> >   };
> >   /* we currently support only two vrings per rvdev */
> > diff --git a/include/linux/remoteproc/qcom_rproc.h 
> > b/include/linux/remoteproc/qcom_rproc.h
> > index 82b211518136..f3d06900f297 100644
> > --- a/include/linux/remoteproc/qcom_rproc.h
> > +++ b/include/linux/remoteproc/qcom_rproc.h
> > @@ -11,12 +11,14 @@ struct notifier_block;
> >    * @QCOM_SSR_AFTER_POWERUP:    Remoteproc is running (start stage)
> >    * @QCOM_SSR_BEFORE_SHUTDOWN:    Remoteproc crashed or shutting down 
> > (stop stage)
> >    * @QCOM_SSR_AFTER_SHUTDOWN:    Remoteproc is down (unprepare stage)
> > + * @QCOM_SSR_NOTIFY_CRASH:    Remoteproc crashed
> >    */
> >   enum qcom_ssr_notify_type {
> >       QCOM_SSR_BEFORE_POWERUP,
> >       QCOM_SSR_AFTER_POWERUP,
> >       QCOM_SSR_BEFORE_SHUTDOWN,
> >       QCOM_SSR_AFTER_SHUTDOWN,
> > +    QCOM_SSR_NOTIFY_CRASH,
> >   };
> >   struct qcom_ssr_notify_data {
> > @@ -29,6 +31,10 @@ struct qcom_ssr_notify_data {
> >   void *qcom_register_ssr_notifier(const char *name, struct 
> > notifier_block *nb);
> >   int qcom_unregister_ssr_notifier(void *notify, struct notifier_block 
> > *nb);
> > +void *qcom_register_ssr_atomic_notifier(const char *name,
> > +                    struct notifier_block *nb);
> > +int qcom_unregister_ssr_atomic_notifier(void *notify,
> > +                    struct notifier_block *nb);
> >   #else
> >   static inline void *qcom_register_ssr_notifier(const char *name,
> > @@ -43,6 +49,17 @@ static inline int qcom_unregister_ssr_notifier(void 
> > *notify,
> >       return 0;
> >   }
> > +static inline void *qcom_register_ssr_atomic_notifier(const char *name,
> > +                              struct notifier_block *nb)
> > +{
> > +    return 0;
> > +}
> > +
> > +static inline int qcom_unregister_ssr_atomic_notifier(void *notify,
> > +                              struct notifier_block *nb)
> > +{
> > +    return 0;
> > +}
> >   #endif
> >   #endif