Subject: Re: [PATCH 6/6] remoteproc: qcom: Add notification types to SSR

From: Mathieu Poirier <[email-masked]>
Date: Thu, 27 Feb 2020 14:59:40 -0700

On Wed, Feb 19, 2020 at 06:57:45PM -0800, Siddharth Gupta wrote:
> The SSR subdevice only adds callback for the unprepare event. Add callbacks
> for unprepare, start and prepare events. The client driver for a particular
> 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 <[email-masked]>
> ---
>  drivers/remoteproc/qcom_common.c | 39 +++++++++++++++++++++++++++++++++++----
>  include/linux/remoteproc.h       | 15 +++++++++++++++
>  2 files changed, 50 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/remoteproc/qcom_common.c b/drivers/remoteproc/qcom_common.c
> index 6714f27..6f04a5b 100644
> --- a/drivers/remoteproc/qcom_common.c
> +++ b/drivers/remoteproc/qcom_common.c
> @@ -183,9 +183,9 @@ EXPORT_SYMBOL_GPL(qcom_remove_smd_subdev);
>   *
>   * Returns pointer to srcu notifier head on success, ERR_PTR on failure.
>   *
> - * This registers the @notify function as handler for restart notifications. As
> - * remote processors are stopped this function will be called, with the rproc
> - * pointer passed as a parameter.
> + * This registers the @notify function as handler for powerup/shutdown
> + * notifications. This function will be invoked inside the callbacks registered
> + * for the ssr subdevice, with the rproc pointer passed as a parameter.
>   */
>  void *qcom_register_ssr_notifier(struct rproc *rproc, struct notifier_block *nb)
>  {
> @@ -227,11 +227,39 @@ 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);
> +
> +	srcu_notifier_call_chain(ssr->rproc_notif_list,
> +				 RPROC_BEFORE_POWERUP, (void *)ssr->name);
> +	return 0;
> +}
> +
> +static int ssr_notify_start(struct rproc_subdev *subdev)
> +{
> +	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> +
> +	srcu_notifier_call_chain(ssr->rproc_notif_list,
> +				 RPROC_AFTER_POWERUP, (void *)ssr->name);
> +	return 0;
> +}
> +
> +static void ssr_notify_stop(struct rproc_subdev *subdev, bool crashed)
> +{
> +	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
> +
> +	srcu_notifier_call_chain(ssr->rproc_notif_list,
> +				 RPROC_BEFORE_SHUTDOWN, (void *)ssr->name);
> +}
> +
> +
>  static void ssr_notify_unprepare(struct rproc_subdev *subdev)
>  {
>  	struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
>  
> -	srcu_notifier_call_chain(ssr->rproc_notif_list, 0, (void *)ssr->name);
> +	srcu_notifier_call_chain(ssr->rproc_notif_list,
> +				 RPROC_AFTER_SHUTDOWN, (void *)ssr->name);
>  }
>  
>  /**
> @@ -248,6 +276,9 @@ void qcom_add_ssr_subdev(struct rproc *rproc, struct qcom_rproc_ssr *ssr,
>  {
>  	ssr->name = ssr_name;
>  	ssr->subdev.name = kstrdup("ssr_notifs", GFP_KERNEL);
> +	ssr->subdev.prepare = ssr_notify_prepare;
> +	ssr->subdev.start = ssr_notify_start;
> +	ssr->subdev.stop = ssr_notify_stop;

Now that I have a better understanding of what this patchset is doing, I realise
my comments in patch 04 won't work.  To differentiate the subdevs of an rproc I
suggest to wrap them in a generic structure with a type and an enum.  That way
you can differenciate between subdevices without having to add to the core.

That being said, I don't understand what patches 5 and 6 are doing...
Registering with the global ssr_notifiers allowed to gracefully shutdown all the
MCUs in the system when one of them would go down.  But now that we are using
the notifier on a per MCU, I really don't see why each subdev couldn't implement
the right prepare/start/stop functions.

Am I missing something here?

>  	ssr->subdev.unprepare = ssr_notify_unprepare;
>  	ssr->rproc_notif_list = kzalloc(sizeof(struct srcu_notifier_head),
>  								GFP_KERNEL);
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index e2f60cc..4be4478 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -449,6 +449,21 @@ struct rproc_dump_segment {
>  };
>  
>  /**
> + * enum rproc_notif_type - Different stages of remoteproc notifications
> + * @RPROC_BEFORE_SHUTDOWN:	unprepare stage of  remoteproc
> + * @RPROC_AFTER_SHUTDOWN:	stop stage of  remoteproc
> + * @RPROC_BEFORE_POWERUP:	prepare stage of  remoteproc
> + * @RPROC_AFTER_POWERUP:	start stage of  remoteproc
> + */
> +enum rproc_notif_type {
> +	RPROC_BEFORE_SHUTDOWN,
> +	RPROC_AFTER_SHUTDOWN,
> +	RPROC_BEFORE_POWERUP,
> +	RPROC_AFTER_POWERUP,
> +	RPROC_MAX
> +};
> +
> +/**
>   * struct rproc - represents a physical remote processor device
>   * @node: list node of this rproc object
>   * @domain: iommu domain
> -- 
> Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 
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