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

Arnaud POULIQUEN
2020-05-04T11:34:59Z

On 4/30/20 10:23 PM, Mathieu Poirier wrote:
> On Wed, Apr 29, 2020 at 10:19:49AM +0200, Arnaud POULIQUEN wrote:
>>
>>
>> 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@linaro.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.
>
> If rproc->sync_ops->stop is not provided then the remoteproc core can't stop the
> remote processor at all after it has synchronised with it. If a usecase
> requires some kind of soft reset then a stop() function that uses a mailbox
> notification or some other mechanism can be provided to tell the remote
> processor to put itself back in startup mode again.
>
> Is this fine with you or there is still something I don't get?

My point here is more around the subdevices. But perhaps i missed something...

In rproc_start rproc_start_subdevices is called, even if sync_start is null.
But in rproc_shutdown rproc_stop is not called, if sync_ops->stop is null.
So rproc_stop_subdevices is not called in this case.
Then if sync_flags.after_stop is false, it looks like that something will go wrong
at next start.

>
>> 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;
>>>