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

Mathieu Poirier
2020-04-30T20:42:38Z

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.

>
> 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?

>
> 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);
> >