Re: [PATCH v3 12/14] remoteproc: Introducing function rproc_set_state_machine()

Arnaud POULIQUEN
2020-05-04T11:58:11Z

On 4/30/20 10:42 PM, Mathieu Poirier wrote:
> On Wed, Apr 29, 2020 at 11:22:28AM +0200, Arnaud POULIQUEN wrote:
>>
>>
>> On 4/24/20 10:01 PM, Mathieu Poirier wrote:
>>> Introducting function rproc_set_state_machine() to add
>>> operations and a set of flags to use when synchronising with
>>> a remote processor.
>>>
>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> ---
>>> drivers/remoteproc/remoteproc_core.c | 54 ++++++++++++++++++++++++
>>> drivers/remoteproc/remoteproc_internal.h | 6 +++
>>> include/linux/remoteproc.h | 3 ++
>>> 3 files changed, 63 insertions(+)
>>>
>>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>>> index 48afa1f80a8f..5c48714e8702 100644
>>> --- a/drivers/remoteproc/remoteproc_core.c
>>> +++ b/drivers/remoteproc/remoteproc_core.c
>>> @@ -2065,6 +2065,59 @@ int devm_rproc_add(struct device *dev, struct rproc *rproc)
>>> }
>>> EXPORT_SYMBOL(devm_rproc_add);
>>>
>>> +/**
>>> + * rproc_set_state_machine() - Set a synchronisation ops and set of flags
>>> + * to use with a remote processor
>>> + * @rproc: The remote processor to work with
>>> + * @sync_ops: The operations to use when synchronising with a remote
>>> + * processor
>>> + * @sync_flags: The flags to use when deciding if the remoteproc core
>>> + * should be synchronising with a remote processor
>>> + *
>>> + * Returns 0 on success, an error code otherwise.
>>> + */
>>> +int rproc_set_state_machine(struct rproc *rproc,
>>> + const struct rproc_ops *sync_ops,
>>> + struct rproc_sync_flags sync_flags)
>>
>> So this API should be called by platform driver only in case of synchronization
>> support, right?
>
> Correct
>
>> In this case i would rename it as there is also a state machine in "normal" boot
>> proposal: rproc_set_sync_machine or rproc_set_sync_state_machine
>
> That is a valid observation - rproc_set_sync_state_machine() sounds descriptive
> enough for me.
>
>>
>>> +{
>>> + if (!rproc || !sync_ops)
>>> + return -EINVAL;
>>> +
>>> + /*
>>> + * No point in going further if we never have to synchronise with
>>> + * the remote processor.
>>> + */
>>> + if (!sync_flags.on_init &&
>>> + !sync_flags.after_stop && !sync_flags.after_crash)
>>> + return 0;
>>> +
>>> + /*
>>> + * Refuse to go further if remoteproc operations have been allocated
>>> + * but they will never be used.
>>> + */
>>> + if (rproc->ops && sync_flags.on_init &&
>>> + sync_flags.after_stop && sync_flags.after_crash)
>>> + return -EINVAL;
>>> +
>>> + /*
>>> + * Don't allow users to set this more than once to avoid situations
>>> + * where the remote processor can't be recovered.
>>> + */
>>> + if (rproc->sync_ops)
>>> + return -EINVAL;
>>> +
>>> + rproc->sync_ops = kmemdup(sync_ops, sizeof(*sync_ops), GFP_KERNEL);
>>> + if (!rproc->sync_ops)
>>> + return -ENOMEM;
>>> +
>>> + rproc->sync_flags = sync_flags;
>>> + /* Tell the core what to do when initialising */
>>> + rproc_set_sync_flag(rproc, RPROC_SYNC_STATE_INIT);
>>
>> Is there a use case where sync_flags.on_init is false and other flags are true?
>
> I haven't seen one yet, which doesn't mean it doesn't exist or won't in the
> future. I wanted to make this as flexible as possible. I started with the idea
> of making synchronisation at initialisation time implicit if
> rproc_set_state_machine() is called but I know it is only a matter of time
> before people come up with some exotic use case where .on_init is false.

So having on_init false but after_crash && after_stop true, means loading the
firmware on first start, and the synchronize with it, right?
Yes probably could be an exotic valid use case. :)

>
>>
>> Look like on_init is useless and should not be exposed to the platform driver.
>> Or comments are missing to explain the usage of it vs the other flags.
>
> Comments added in remoteproc_internal.h and the new section in
> Documentation/remoteproc.txt aren't sufficient? Can you give me a hint as to
> what you think is missing?

IMO something is quite confusing...
On one side on_init can be set to false.
But on the other side the flag is set by call rproc_set_state_machine.
In Documentation/remoteproc.txt rproc_set_state_machine description is:

"This function should be called for cases where the remote processor has
been started by another entity, be it a boot loader or trusted environment,
and the remoteproc core is to synchronise with the remote processor rather
then boot it."

So how on_init could be false if "the remote processor has
been started by another entity"?

Regards,
Arnaud

>
>>
>> Regards,
>> Arnaud
>>
>>> +
>>> + return 0;
>>> +}
>>> +EXPORT_SYMBOL(rproc_set_state_machine);
>>> +
>>> /**
>>> * rproc_type_release() - release a remote processor instance
>>> * @dev: the rproc's device
>>> @@ -2088,6 +2141,7 @@ static void rproc_type_release(struct device *dev)
>>> kfree_const(rproc->firmware);
>>> kfree_const(rproc->name);
>>> kfree(rproc->ops);
>>> + kfree(rproc->sync_ops);
>>> kfree(rproc);
>>> }
>>>
>>> diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
>>> index 7dcc0a26892b..c1a293a37c78 100644
>>> --- a/drivers/remoteproc/remoteproc_internal.h
>>> +++ b/drivers/remoteproc/remoteproc_internal.h
>>> @@ -27,6 +27,8 @@ struct rproc_debug_trace {
>>> /*
>>> * enum rproc_sync_states - remote processsor sync states
>>> *
>>> + * @RPROC_SYNC_STATE_INIT state to use when the remoteproc core
>>> + * is initialising.
>>> * @RPROC_SYNC_STATE_SHUTDOWN state to use after the remoteproc core
>>> * has shutdown (rproc_shutdown()) the
>>> * remote processor.
>>> @@ -39,6 +41,7 @@ struct rproc_debug_trace {
>>> * operation to use.
>>> */
>>> enum rproc_sync_states {
>>> + RPROC_SYNC_STATE_INIT,
>>> RPROC_SYNC_STATE_SHUTDOWN,
>>> RPROC_SYNC_STATE_CRASHED,
>>> };
>>> @@ -47,6 +50,9 @@ static inline void rproc_set_sync_flag(struct rproc *rproc,
>>> enum rproc_sync_states state)
>>> {
>>> switch (state) {
>>> + case RPROC_SYNC_STATE_INIT:
>>> + rproc->sync_with_rproc = rproc->sync_flags.on_init;
>>> + break;
>>> case RPROC_SYNC_STATE_SHUTDOWN:
>>> rproc->sync_with_rproc = rproc->sync_flags.after_stop;
>>> break;
>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>> index ceb3b2bba824..a75ed92b3de6 100644
>>> --- a/include/linux/remoteproc.h
>>> +++ b/include/linux/remoteproc.h
>>> @@ -619,6 +619,9 @@ struct rproc *rproc_get_by_child(struct device *dev);
>>> struct rproc *rproc_alloc(struct device *dev, const char *name,
>>> const struct rproc_ops *ops,
>>> const char *firmware, int len);
>>> +int rproc_set_state_machine(struct rproc *rproc,
>>> + const struct rproc_ops *sync_ops,
>>> + struct rproc_sync_flags sync_flags);
>>> void rproc_put(struct rproc *rproc);
>>> int rproc_add(struct rproc *rproc);
>>> int rproc_del(struct rproc *rproc);
>>>