linux-kernel - Re: [PATCH v3 10/14] remoteproc: Deal with synchronisation when shutting down

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Date:   Wed, 29 Apr 2020 10:19:49 +0200
From:   Arnaud POULIQUEN <arnaud.pouliquen@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        <bjorn.andersson@...aro.org>, <ohad@...ery.com>
CC:     <loic.pallardy@...com>, <s-anna@...com>,
        <linux-remoteproc@...r.kernel.org>, <corbet@....net>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 10/14] remoteproc: Deal with synchronisation when
 shutting down



On 4/24/20 10:01 PM, Mathieu Poirier wrote:
> The remoteproc core must not allow function rproc_shutdown() to
> proceed if currently synchronising with a remote processor and
> the synchronisation operations of that remote processor does not
> support it.  Also part of the process is to set the synchronisation
> flag so that the remoteproc core can make the right decisions when
> restarting the system.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  drivers/remoteproc/remoteproc_core.c     | 32 ++++++++++++++++++++++++
>  drivers/remoteproc/remoteproc_internal.h |  7 ++++++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 3a84a38ba37b..48afa1f80a8f 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1849,6 +1849,27 @@ int rproc_boot(struct rproc *rproc)
>  }
>  EXPORT_SYMBOL(rproc_boot);
>  
> +static bool rproc_can_shutdown(struct rproc *rproc)
> +{
> +	/*
> +	 * The remoteproc core is the lifecycle manager, no problem
> +	 * calling for a shutdown.
> +	 */
> +	if (!rproc_needs_syncing(rproc))
> +		return true;
> +
> +	/*
> +	 * The remoteproc has been loaded by another entity (as per above
> +	 * condition) and the platform code has given us the capability
> +	 * of stopping it.
> +	 */
> +	if (rproc->sync_ops->stop)
> +		return true;

This means that if rproc->sync_ops->stop is null rproc_stop_subdevices will not
be called? seems not symmetric with the start sequence.
Probably not useful to test it here as condition is already handled in rproc_stop_device...

Regards
Arnaud
> +
> +	/* Any other condition should not be allowed */
> +	return false;
> +}
> +
>  /**
>   * rproc_shutdown() - power off the remote processor
>   * @rproc: the remote processor
> @@ -1879,6 +1900,9 @@ void rproc_shutdown(struct rproc *rproc)
>  		return;
>  	}
>  
> +	if (!rproc_can_shutdown(rproc))
> +		goto out;
> +
>  	/* if the remote proc is still needed, bail out */
>  	if (!atomic_dec_and_test(&rproc->power))
>  		goto out;
> @@ -1898,6 +1922,14 @@ void rproc_shutdown(struct rproc *rproc)
>  	kfree(rproc->cached_table);
>  	rproc->cached_table = NULL;
>  	rproc->table_ptr = NULL;
> +
> +	/*
> +	 * The remote processor has been switched off - tell the core what
> +	 * operation to use from hereon, i.e whether an external entity will
> +	 * reboot the remote processor or it is now the remoteproc core's
> +	 * responsability.
> +	 */
> +	rproc_set_sync_flag(rproc, RPROC_SYNC_STATE_SHUTDOWN);
>  out:
>  	mutex_unlock(&rproc->lock);
>  }
> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
> index 61500981155c..7dcc0a26892b 100644
> --- a/drivers/remoteproc/remoteproc_internal.h
> +++ b/drivers/remoteproc/remoteproc_internal.h
> @@ -27,6 +27,9 @@ struct rproc_debug_trace {
>  /*
>   * enum rproc_sync_states - remote processsor sync states
>   *
> + * @RPROC_SYNC_STATE_SHUTDOWN	state to use after the remoteproc core
> + *				has shutdown (rproc_shutdown()) the
> + *				remote processor.
>   * @RPROC_SYNC_STATE_CRASHED	state to use after the remote processor
>   *				has crashed but has not been recovered by
>   *				the remoteproc core yet.
> @@ -36,6 +39,7 @@ struct rproc_debug_trace {
>   * operation to use.
>   */
>  enum rproc_sync_states {
> +	RPROC_SYNC_STATE_SHUTDOWN,
>  	RPROC_SYNC_STATE_CRASHED,
>  };
>  
> @@ -43,6 +47,9 @@ static inline void rproc_set_sync_flag(struct rproc *rproc,
>  				       enum rproc_sync_states state)
>  {
>  	switch (state) {
> +	case RPROC_SYNC_STATE_SHUTDOWN:
> +		rproc->sync_with_rproc = rproc->sync_flags.after_stop;
> +		break;
>  	case RPROC_SYNC_STATE_CRASHED:
>  		rproc->sync_with_rproc = rproc->sync_flags.after_crash;
>  		break;
>