linux-kernel - Re: [PATCH v3 09/14] remoteproc: Deal with synchronisation when crashing

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Date:   Tue, 5 May 2020 18:01:56 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     ohad@...ery.com, loic.pallardy@...com, arnaud.pouliquen@...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 09/14] remoteproc: Deal with synchronisation when
 crashing

On Fri 24 Apr 13:01 PDT 2020, Mathieu Poirier wrote:

> Refactor function rproc_trigger_recovery() in order to avoid
> reloading the firmware image when synchronising with a remote
> processor rather than booting it.  Also part of the process,
> properly set the synchronisation flag in order to properly
> recover the system.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>  drivers/remoteproc/remoteproc_core.c     | 23 ++++++++++++++------
>  drivers/remoteproc/remoteproc_internal.h | 27 ++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index ef88d3e84bfb..3a84a38ba37b 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1697,7 +1697,7 @@ static void rproc_coredump(struct rproc *rproc)
>   */
>  int rproc_trigger_recovery(struct rproc *rproc)
>  {
> -	const struct firmware *firmware_p;
> +	const struct firmware *firmware_p = NULL;
>  	struct device *dev = &rproc->dev;
>  	int ret;
>  
> @@ -1718,14 +1718,16 @@ int rproc_trigger_recovery(struct rproc *rproc)
>  	/* generate coredump */
>  	rproc_coredump(rproc);
>  
> -	/* load firmware */
> -	ret = request_firmware(&firmware_p, rproc->firmware, dev);
> -	if (ret < 0) {
> -		dev_err(dev, "request_firmware failed: %d\n", ret);
> -		goto unlock_mutex;
> +	/* load firmware if need be */
> +	if (!rproc_needs_syncing(rproc)) {
> +		ret = request_firmware(&firmware_p, rproc->firmware, dev);
> +		if (ret < 0) {
> +			dev_err(dev, "request_firmware failed: %d\n", ret);
> +			goto unlock_mutex;
> +		}
>  	}
>  
> -	/* boot the remote processor up again */
> +	/* boot up or synchronise with the remote processor again */
>  	ret = rproc_start(rproc, firmware_p);
>  
>  	release_firmware(firmware_p);
> @@ -1761,6 +1763,13 @@ static void rproc_crash_handler_work(struct work_struct *work)
>  	dev_err(dev, "handling crash #%u in %s\n", ++rproc->crash_cnt,
>  		rproc->name);
>  
> +	/*
> +	 * The remote processor has crashed - tell the core what operation
> +	 * to use from hereon, i.e whether an external entity will reboot
> +	 * the MCU or it is now the remoteproc core's responsability.
> +	 */
> +	rproc_set_sync_flag(rproc, RPROC_SYNC_STATE_CRASHED);

If I follow the logic correctly, you're essentially using
rproc->sync_with_rproc to pass an additional parameter down through
rproc_trigger_recovery() to tell everyone below to "load firmware and
boot the core or not".

And given that the comment alludes to some unknown logic determining the
continuation I think it would be much preferable to essentially just
pass rproc->sync_flags.after_crash down through these functions.


And per my comment on a previous patch, is there any synchronization
with the remote controller when this happens?

Regards,
Bjorn

> +
>  	mutex_unlock(&rproc->lock);
>  
>  	if (!rproc->recovery_disabled)
> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
> index 3985c084b184..61500981155c 100644
> --- a/drivers/remoteproc/remoteproc_internal.h
> +++ b/drivers/remoteproc/remoteproc_internal.h
> @@ -24,6 +24,33 @@ struct rproc_debug_trace {
>  	struct rproc_mem_entry trace_mem;
>  };
>  
> +/*
> + * enum rproc_sync_states - remote processsor sync states
> + *
> + * @RPROC_SYNC_STATE_CRASHED	state to use after the remote processor
> + *				has crashed but has not been recovered by
> + *				the remoteproc core yet.
> + *
> + * Keeping these separate from the enum rproc_state in order to avoid
> + * introducing coupling between the state of the MCU and the synchronisation
> + * operation to use.
> + */
> +enum rproc_sync_states {
> +	RPROC_SYNC_STATE_CRASHED,
> +};
> +
> +static inline void rproc_set_sync_flag(struct rproc *rproc,
> +				       enum rproc_sync_states state)
> +{
> +	switch (state) {
> +	case RPROC_SYNC_STATE_CRASHED:
> +		rproc->sync_with_rproc = rproc->sync_flags.after_crash;
> +		break;
> +	default:
> +		break;
> +	}
> +}
> +
>  /* from remoteproc_core.c */
>  void rproc_release(struct kref *kref);
>  irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int vq_id);
> -- 
> 2.20.1
>