Subject: Re: [PATCH 6/6] remoteproc: qcom: Add notification types to SSR

From: [email-masked]
Date: Tue, 03 Mar 2020 15:30:37 -0800

On 2020-03-03 10:05, Mathieu Poirier wrote:
> On Mon, 2 Mar 2020 at 13:54, <[email-masked]> wrote:
>> 
>> On 2020-02-28 10:38, Mathieu Poirier wrote:
>> > On Thu, Feb 27, 2020 at 04:00:21PM -0800, [email-masked]
>> > wrote:
>> >> On 2020-02-27 13:59, Mathieu Poirier wrote:
>> >> > On Wed, Feb 19, 2020 at 06:57:45PM -0800, Siddharth Gupta wrote:
>> >> > > The SSR subdevice only adds callback for the unprepare event. Add
>> >> > > callbacks
>> >> > > for unprepare, start and prepare events. The client driver for a
>> >> > > particular
>> >> > > remoteproc might be interested in knowing the status of the remoteproc
>> >> > > while undergoing SSR, not just when the remoteproc has finished
>> >> > > shutting
>> >> > > down.
>> >> > >
>> >> > > Signed-off-by: Siddharth Gupta <[email-masked]>
>> >> > > ---
>> >> > >  drivers/remoteproc/qcom_common.c | 39
>> >> > > +++++++++++++++++++++++++++++++++++----
>> >> > >  include/linux/remoteproc.h       | 15 +++++++++++++++
>> >> > >  2 files changed, 50 insertions(+), 4 deletions(-)
>> >> > >
>> >> > > diff --git a/drivers/remoteproc/qcom_common.c
>> >> > > b/drivers/remoteproc/qcom_common.c
>> >> > > index 6714f27..6f04a5b 100644
>> >> > > --- a/drivers/remoteproc/qcom_common.c
>> >> > > +++ b/drivers/remoteproc/qcom_common.c
>> >> > > @@ -183,9 +183,9 @@ EXPORT_SYMBOL_GPL(qcom_remove_smd_subdev);
>> >> > >   *
>> >> > >   * Returns pointer to srcu notifier head on success, ERR_PTR on
>> >> > > failure.
>> >> > >   *
>> >> > > - * This registers the @notify function as handler for restart
>> >> > > notifications. As
>> >> > > - * remote processors are stopped this function will be called, with
>> >> > > the rproc
>> >> > > - * pointer passed as a parameter.
>> >> > > + * This registers the @notify function as handler for
>> >> > > powerup/shutdown
>> >> > > + * notifications. This function will be invoked inside the
>> >> > > callbacks registered
>> >> > > + * for the ssr subdevice, with the rproc pointer passed as a
>> >> > > parameter.
>> >> > >   */
>> >> > >  void *qcom_register_ssr_notifier(struct rproc *rproc, struct
>> >> > > notifier_block *nb)
>> >> > >  {
>> >> > > @@ -227,11 +227,39 @@ int qcom_unregister_ssr_notifier(void *notify,
>> >> > > struct notifier_block *nb)
>> >> > >  }
>> >> > >  EXPORT_SYMBOL_GPL(qcom_unregister_ssr_notifier);
>> >> > >
>> >> > > +static int ssr_notify_prepare(struct rproc_subdev *subdev)
>> >> > > +{
>> >> > > +        struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
>> >> > > +
>> >> > > +        srcu_notifier_call_chain(ssr->rproc_notif_list,
>> >> > > +                                 RPROC_BEFORE_POWERUP, (void *)ssr->name);
>> >> > > +        return 0;
>> >> > > +}
>> >> > > +
>> >> > > +static int ssr_notify_start(struct rproc_subdev *subdev)
>> >> > > +{
>> >> > > +        struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
>> >> > > +
>> >> > > +        srcu_notifier_call_chain(ssr->rproc_notif_list,
>> >> > > +                                 RPROC_AFTER_POWERUP, (void *)ssr->name);
>> >> > > +        return 0;
>> >> > > +}
>> >> > > +
>> >> > > +static void ssr_notify_stop(struct rproc_subdev *subdev, bool
>> >> > > crashed)
>> >> > > +{
>> >> > > +        struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
>> >> > > +
>> >> > > +        srcu_notifier_call_chain(ssr->rproc_notif_list,
>> >> > > +                                 RPROC_BEFORE_SHUTDOWN, (void *)ssr->name);
>> >> > > +}
>> >> > > +
>> >> > > +
>> >> > >  static void ssr_notify_unprepare(struct rproc_subdev *subdev)
>> >> > >  {
>> >> > >          struct qcom_rproc_ssr *ssr = to_ssr_subdev(subdev);
>> >> > >
>> >> > > -        srcu_notifier_call_chain(ssr->rproc_notif_list, 0, (void
>> >> > > *)ssr->name);
>> >> > > +        srcu_notifier_call_chain(ssr->rproc_notif_list,
>> >> > > +                                 RPROC_AFTER_SHUTDOWN, (void *)ssr->name);
>> >> > >  }
>> >> > >
>> >> > >  /**
>> >> > > @@ -248,6 +276,9 @@ void qcom_add_ssr_subdev(struct rproc *rproc,
>> >> > > struct qcom_rproc_ssr *ssr,
>> >> > >  {
>> >> > >          ssr->name = ssr_name;
>> >> > >          ssr->subdev.name = kstrdup("ssr_notifs", GFP_KERNEL);
>> >> > > +        ssr->subdev.prepare = ssr_notify_prepare;
>> >> > > +        ssr->subdev.start = ssr_notify_start;
>> >> > > +        ssr->subdev.stop = ssr_notify_stop;
>> >> >
>> >> > Now that I have a better understanding of what this patchset is doing, I
>> >> > realise
>> >> > my comments in patch 04 won't work.  To differentiate the subdevs of an
>> >> > rproc I
>> >> > suggest to wrap them in a generic structure with a type and an enum.
>> >> > That way
>> >> > you can differenciate between subdevices without having to add to the
>> >> > core.
>> >> Ok. I can try that.
>> >> >
>> >> > That being said, I don't understand what patches 5 and 6 are doing...
>> >> > Registering with the global ssr_notifiers allowed to gracefully shutdown
>> >> > all the
>> >> > MCUs in the system when one of them would go down.  But now that we are
>> >> > using
>> >> > the notifier on a per MCU, I really don't see why each subdev couldn't
>> >> > implement
>> >> > the right prepare/start/stop functions.
>> >> >
>> >> > Am I missing something here?
>> >> We only want kernel clients to be notified when the Remoteproc they
>> >> are
>> >> interested
>> >> in changes state. For e.g. audio kernel driver should be notified when
>> >> audio
>> >> processor goes down but it does not care about any other remoteproc.
>> >> If you are suggesting that these kernel clients be added as subdevices
>> >> then
>> >> we will end up having many subdevices registered to each remoteproc.
>> >> So we
>> >> implemented a notifier chain per Remoteproc. This keeps the SSR
>> >> notifications as
>> >> the subdevice per remoteproc, and all interested clients can register
>> >> to it.
>> >
>> > It seems like I am missing information...  Your are referring to
>> > "kernel
>> > clients" and as such I must assume some drivers that are not part of
>> > the
>> > remoteproc/rpmsg subsystems are calling qcom_register_ssr_notifier().
>> > I must
>> Yes these are not part of remoteproc framework and they will register
>> for notifications.
>> > also assume these drivers (or that functionality) are not yet upsream
>> > because
>> > all I can see calling qcom_register_ssr_notifier() is
>> > qcom_glink_ssr_probe().
>> Correct.These are not upstreamed.
> 
> Ok, things are starting to make sense.
> 
>> >
>> > Speaking of which, what is the role of the qcom_glink_ssr_driver?  Is
>> > the glink
>> > device that driver is handling the same as the glink device registed in
>> > adsp_probe() and q6v5_probe()?
>> glink ssr driver will send out notifications to remoteprocs that have
>> opened the
>> "glink_ssr" channel that some subsystem has gone down or booted up. 
>> This
>> helps notify
>> neighboring subsystems about change in state of any other subsystem.
> 
> I am still looking for an answer to my second question.
Yes its the subdevice of the glink device that is registered in 
adsp_probe.
It uses the "glink_ssr" glink channel.
> 
>> >
>> >> >
>> >> >
>> >> > >          ssr->subdev.unprepare = ssr_notify_unprepare;
>> >> > >          ssr->rproc_notif_list = kzalloc(sizeof(struct srcu_notifier_head),
>> >> > >                                                                  GFP_KERNEL);
>> >> > > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>> >> > > index e2f60cc..4be4478 100644
>> >> > > --- a/include/linux/remoteproc.h
>> >> > > +++ b/include/linux/remoteproc.h
>> >> > > @@ -449,6 +449,21 @@ struct rproc_dump_segment {
>> >> > >  };
>> >> > >
>> >> > >  /**
>> >> > > + * enum rproc_notif_type - Different stages of remoteproc
>> >> > > notifications
>> >> > > + * @RPROC_BEFORE_SHUTDOWN:      unprepare stage of  remoteproc
>> >> > > + * @RPROC_AFTER_SHUTDOWN:       stop stage of  remoteproc
>> >> > > + * @RPROC_BEFORE_POWERUP:       prepare stage of  remoteproc
>> >> > > + * @RPROC_AFTER_POWERUP:        start stage of  remoteproc
>> >> > > + */
>> >> > > +enum rproc_notif_type {
>> >> > > +        RPROC_BEFORE_SHUTDOWN,
>> >> > > +        RPROC_AFTER_SHUTDOWN,
>> >> > > +        RPROC_BEFORE_POWERUP,
>> >> > > +        RPROC_AFTER_POWERUP,
>> >> > > +        RPROC_MAX
>> >> > > +};
>> >> > > +
>> >> > > +/**
>> >> > >   * struct rproc - represents a physical remote processor device
>> >> > >   * @node: list node of this rproc object
>> >> > >   * @domain: iommu domain
>> >> > > --
>> >> > > Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> >> > > a Linux Foundation Collaborative Project
>> >> > >
>> >> > > _______________________________________________
>> >> > > linux-arm-kernel mailing list
>> >> > > [email-masked]
>> >> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>> 
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