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

From: rishabhb
Date: Mon Mar 02 2020 - 15:54:28 EST


On 2020-02-28 10:38, Mathieu Poirier wrote:
On Thu, Feb 27, 2020 at 04:00:21PM -0800, rishabhb@xxxxxxxxxxxxxx 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 <sidgup@xxxxxxxxxxxxxx>
> > ---
> > 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.

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.

>
>
> > 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
> >
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