Date:   Thu, 15 Jun 2023 16:10:13 +0530
From:   Vignesh Viswanathan <quic_viswanat@...cinc.com>
To:     Mukesh Ojha <quic_mojha@...cinc.com>, <agross@...nel.org>,
        <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
        <mathieu.poirier@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>
CC:     <quic_srichara@...cinc.com>, <quic_varada@...cinc.com>,
        <quic_kathirav@...cinc.com>, <quic_devipriy@...cinc.com>,
        <quic_sjaganat@...cinc.com>
Subject: Re: [PATCH] remoteproc: qcom: Add NOTIFY_FATAL event type to SSR
 subdevice



On 5/29/2023 9:27 AM, Vignesh Viswanathan wrote:
> Gentle Reminder.
> 
> On 5/22/2023 3:03 PM, Mukesh Ojha wrote:
>>
>>
>> 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@...cinc.com>
>>
>> -- Mukesh
>>
Gentle Reminder!

Thanks,
Vignesh

>>
>>>
>>> -Mukesh
>>>>
>>>> Signed-off-by: Vignesh Viswanathan <quic_viswanat@...cinc.com>
>>>> ---
>>>>   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
>>>

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