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

Mathieu Poirier
2020-05-05T21:43:23Z

On Mon, May 04, 2020 at 01:57:59PM +0200, Arnaud POULIQUEN wrote:
>
>
> 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"?

I see your point and I think it is a question of documentation. I will rephrase
this to be more accurate.

>
> 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);
> >>>