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Message-ID: <cfe32c1c-6d9b-1c74-c7d1-6597591edf77@quicinc.com>
Date:   Mon, 22 May 2023 15:03:14 +0530
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Subject: Re: [PATCH] remoteproc: qcom: Add NOTIFY_FATAL event type to SSR
 subdevice
Content-Language: en-US
From:   Mukesh Ojha <quic_mojha@quicinc.com>
To:     Vignesh Viswanathan <quic_viswanat@quicinc.com>,
        <agross@kernel.org>, <andersson@kernel.org>,
        <konrad.dybcio@linaro.org>, <mathieu.poirier@linaro.org>,
        <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-remoteproc@vger.kernel.org>
CC:     <quic_srichara@quicinc.com>, <quic_varada@quicinc.com>,
        <quic_kathirav@quicinc.com>, <quic_devipriy@quicinc.com>,
        <quic_sjaganat@quicinc.com>
References: <20230503062146.3891-1-quic_viswanat@quicinc.com>
 <f7a0c15d-a7d7-c2ed-875d-c8c24ebf0dab@quicinc.com>
In-Reply-To: <f7a0c15d-a7d7-c2ed-875d-c8c24ebf0dab@quicinc.com>
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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@quicinc.com>

-- Mukesh


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