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Message-ID: <3687b420-0993-7f76-7116-114b1784de05@quicinc.com>
Date:   Mon, 29 May 2023 09:27:14 +0530
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Subject: Re: [PATCH] remoteproc: qcom: Add NOTIFY_FATAL event type to SSR
 subdevice
To:     Mukesh Ojha <quic_mojha@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>
 <cfe32c1c-6d9b-1c74-c7d1-6597591edf77@quicinc.com>
Content-Language: en-US
From:   Vignesh Viswanathan <quic_viswanat@quicinc.com>
In-Reply-To: <cfe32c1c-6d9b-1c74-c7d1-6597591edf77@quicinc.com>
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Precedence: bulk

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@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
>>