linux-kernel - Re: [PATCH v4 2/2] remoteproc: qcom: Add notification types to SSR

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Date:   Thu, 18 Jun 2020 18:00:34 -0500
From:   Alex Elder <elder@...e.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     bjorn.andersson@...aro.org, tsoni@...eaurora.org,
        psodagud@...eaurora.org, sidgup@...eaurora.org
Subject: Re: [PATCH v4 2/2] remoteproc: qcom: Add notification types to SSR

On 5/27/20 10:34 PM, Rishabh Bhatnagar wrote:
> From: Siddharth Gupta <sidgup@...eaurora.org>
> 
> The SSR subdevice only adds callback for the unprepare event. Add callbacks
> for unprepare, start and prepare events. The client driver for a particular

   for prepare, start, and stop events

> remoteproc might be interested in knowing the status of the remoteproc
> while undergoing SSR, not just when the remoteproc has finished shutting
> down.
> 
> Signed-off-by: Siddharth Gupta <sidgup@...eaurora.org>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> ---
>   drivers/remoteproc/qcom_common.c      | 46 +++++++++++++++++++++++++++++++++--
>   include/linux/remoteproc/qcom_rproc.h | 14 +++++++++++
>   2 files changed, 58 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/qcom_common.c b/drivers/remoteproc/qcom_common.c
> index 61ff2dd..5c5a1eb 100644
> --- a/drivers/remoteproc/qcom_common.c
> +++ b/drivers/remoteproc/qcom_common.c
> @@ -228,7 +228,7 @@ struct qcom_ssr_subsystem *qcom_ssr_get_subsys(const char *name)
>    *
>    * This registers the @nb notifier block as part the notifier chain for a
>    * remoteproc associated with @name. The notifier block's callback
> - * will be invoked when the particular remote processor is stopped.
> + * will be invoked when the particular remote processor is started/stopped.

Maybe something more like:
   will be invoked when an SSR event occurs for the named
   remote processor.

>    */
>   void *qcom_register_ssr_notifier(const char *name, struct notifier_block *nb)
>   {
> @@ -258,6 +258,44 @@ int qcom_unregister_ssr_notifier(void *notify, struct notifier_block *nb)
>   }
>   EXPORT_SYMBOL_GPL(qcom_unregister_ssr_notifier);
>   
> +static int ssr_notify_prepare(struct rproc_subdev *subdev)
> +{
> +	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> +	struct qcom_ssr_notif_data data = {
> +		.name = ssr->info->name,
> +		.crashed = false,
> +	};
> +
> +	srcu_notifier_call_chain(&ssr->info->notifier_list,
> +				 QCOM_SSR_BEFORE_POWERUP, &data);
> +	return 0;
> +}
> +
> +static int ssr_notify_start(struct rproc_subdev *subdev)
> +{
> +	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> +	struct qcom_ssr_notif_data data = {
> +		.name = ssr->info->name,
> +		.crashed = false,
> +	};
> +
> +	srcu_notifier_call_chain(&ssr->info->notifier_list,
> +				 QCOM_SSR_AFTER_POWERUP, &data);
> +	return 0;
> +}
> +
> +static void ssr_notify_stop(struct rproc_subdev *subdev, bool crashed)
> +{
> +	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> +	struct qcom_ssr_notif_data data = {
> +		.name = ssr->info->name,
> +		.crashed = crashed,
> +	};
> +
> +	srcu_notifier_call_chain(&ssr->info->notifier_list,
> +				 QCOM_SSR_BEFORE_SHUTDOWN, &data);
> +}
> +
>   static void ssr_notify_unprepare(struct rproc_subdev *subdev)
>   {
>   	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> @@ -266,7 +304,8 @@ static void ssr_notify_unprepare(struct rproc_subdev *subdev)
>   		.crashed = false,
>   	};
>   
> -	srcu_notifier_call_chain(&ssr->info->notifier_list, 0, &data);
> +	srcu_notifier_call_chain(&ssr->info->notifier_list,
> +				 QCOM_SSR_AFTER_SHUTDOWN, &data);
>   }
>   
>   
> @@ -294,6 +333,9 @@ void qcom_add_ssr_subdev(struct rproc *rproc, struct qcom_rproc_ssr *ssr,
>   
>   	mutex_unlock(&qcom_ssr_subsys_lock);
>   	ssr->info = info;
> +	ssr->subdev.prepare = ssr_notify_prepare;
> +	ssr->subdev.start = ssr_notify_start;
> +	ssr->subdev.stop = ssr_notify_stop;
>   	ssr->subdev.unprepare = ssr_notify_unprepare;
>   
>   	rproc_add_subdev(rproc, &ssr->subdev);
> diff --git a/include/linux/remoteproc/qcom_rproc.h b/include/linux/remoteproc/qcom_rproc.h
> index 58422b1..a558183 100644
> --- a/include/linux/remoteproc/qcom_rproc.h
> +++ b/include/linux/remoteproc/qcom_rproc.h
> @@ -5,6 +5,20 @@
>   
>   #if IS_ENABLED(CONFIG_QCOM_RPROC_COMMON)
>   
> +/**
> + * enum qcom_ssr_notif_type - Different stages of remoteproc notifications
> + * @QCOM_SSR_BEFORE_SHUTDOWN:	unprepare stage of  remoteproc
> + * @QCOM_SSR_AFTER_SHUTDOWN:	stop stage of  remoteproc
> + * @QCOM_SSR_BEFORE_POWERUP:	prepare stage of  remoteproc
> + * @QCOM_SSR_AFTER_POWERUP:	start stage of  remoteproc

I think your explanations of these symbols are less clear than
the symbol names themselves...  In any case, I wouldn't refer
to these as "stages of notifications" but instead something
more like startup/shutdown related events for a remote processor.

I personally might have ordered them differently too:
So maybe more like:
	BEFORE_POWERUP	Remoteproc about to start (prepare)
	AFTER_POWERUP	Remoteproc is running (start)
	BEFORE_SHUTDOWN	Remoteproc crashed, or shutting down (stop)
	AFTER_SHUTDOWN	Remoteproc is down (unprepare)

					-Alex
	
> + */
> +enum qcom_ssr_notif_type {
> +	QCOM_SSR_BEFORE_SHUTDOWN,
> +	QCOM_SSR_AFTER_SHUTDOWN,
> +	QCOM_SSR_BEFORE_POWERUP,
> +	QCOM_SSR_AFTER_POWERUP,
> +};
> +
>   struct qcom_ssr_notif_data {
>   	const char *name;
>   	bool crashed;
>