[PATCH v4 00/13] SCMI Notifications Core Support

Cristian Marussi
2020-03-04T16:26:38Z

Hi all,

this series wants to introduce SCMI Notification Support, built on top of
the standard Kernel notification chain subsystem.

At initialization time each SCMI Protocol takes care to register with the
new SCMI notification core the set of its own events which it intends to
support.

Using the API exposed via scmi_handle.notify_ops a Kernel user can register
its own notifier_t callback (via a notifier_block as usual) against any
registered event as identified by the tuple:

(proto_id, event_id, src_id)

where src_id represents a generic source identifier which is protocol
dependent like domain_id, performance_id, sensor_id and so forth.
(users can anyway do NOT provide any src_id, and subscribe instead to ALL
the existing (if any) src_id sources for that proto_id/evt_id combination)

Each of the above tuple-specified event will be served on its own dedicated
blocking notification chain, dynamically allocated on-demand when at least
one user has shown interest on that event.

Upon a notification delivery all the users' registered notifier_t callbacks
will be in turn invoked and fed with the event_id as @action param and a
generated custom per-event struct _report as @data param.
(as in include/linux/scmi_protocol.h)

The final step of notification delivery via users' callback invocation is
instead delegated to a pool of deferred workers (Kernel cmwq): each
SCMI protocol has its own dedicated worker and dedicated queue to push
events from the rx ISR to the worker.

Based on scmi-next 5.6 [1], on top of:

commit 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of
the transport type")

This series has been tested on JUNO with an experimental firmware only
supporting Perf Notifications.

Thanks

Cristian
----

v3 --> v4:
- dropped RFC tag
- avoid one unneeded evt payload memcpy on the ISR RC code path by
redesigning dispatcher to handle partial queue-reads (in_flight events,
only header)
- fixed the initialization issue exposed by late SCMI modules loading by
reviewing the init process to support possible late events registrations
by protocols and early callbacks registrations by users (pending)
- cleanup/simplification of exit path: SCMI protocols are generally never
de-initialized after the initial device creation, so do not deinit
notification core either (we do halt the delivery, stop the wq and empty
the queues though)
- reduced contention on regustered_events_handler to the minimum during
delivery by splitting the common registered_events_handlers hashtable
into a number of per-protocol tables
- converted registered_protocols and registered_events hastable to
fixed size arrays: simpler and lockless in our usage scenario

v2 --> v3:
- added platform instance awareness to the notification core: a
notification instance is created for each known handle
- reviewed notification core initialization and shutdown process
- removed generic non-handle-rooted registration API
- added WQ_SYSFS flag to workqueue instance

v1 --> v2:
- dropped anti-tampering patch
- rebased on top of scmi-for-next-5.6, which includes Viresh series that
make SCMI core independent of transport (5c8a47a5a91d)
- add a few new SCMI transport methods on top of Viresh patch to address
needs of SCMI Notifications
- reviewed/renamed scmi_handle_xfer_delayed_resp()
- split main SCMI Notification core patch (~1k lines) into three chunks:
protocol-registration / callbacks-registration / dispatch-and-delivery
- removed awkward usage of IDR maps in favour of pure hashtables
- added enable/disable refcounting in notification core (was broken in v1)
- removed per-protocol candidate API: a single generic API is now proposed
instead of scmi_register_<proto>_event_notifier(evt_id, *src_id, *nb)
- added handle->notify_ops as an alternative notification API
for scmi_driver
- moved ALL_SRCIDs enabled handling from protocol code to core code
- reviewed protocol registration/unregistration logic to use devres
- reviewed cleanup phase on shutdown
- fixed ERROR: reference preceded by free as reported by kbuild test robot

[1] git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git

Cristian Marussi (10):
firmware: arm_scmi: Add notifications support in transport layer
firmware: arm_scmi: Add notification protocol-registration
firmware: arm_scmi: Add notification callbacks-registration
firmware: arm_scmi: Add notification dispatch and delivery
firmware: arm_scmi: Enable notification core
firmware: arm_scmi: Add Power notifications support
firmware: arm_scmi: Add Perf notifications support
firmware: arm_scmi: Add Sensor notifications support
firmware: arm_scmi: Add Reset notifications support
firmware: arm_scmi: Add Base notifications support

Sudeep Holla (3):
firmware: arm_scmi: Add receive buffer support for notifications
firmware: arm_scmi: Update protocol commands and notification list
firmware: arm_scmi: Add support for notifications message processing

drivers/firmware/arm_scmi/Makefile | 2 +-
drivers/firmware/arm_scmi/base.c | 116 +++
drivers/firmware/arm_scmi/common.h | 12 +
drivers/firmware/arm_scmi/driver.c | 118 ++-
drivers/firmware/arm_scmi/mailbox.c | 17 +
drivers/firmware/arm_scmi/notify.c | 1471 +++++++++++++++++++++++++++
drivers/firmware/arm_scmi/notify.h | 78 ++
drivers/firmware/arm_scmi/perf.c | 135 +++
drivers/firmware/arm_scmi/power.c | 129 +++
drivers/firmware/arm_scmi/reset.c | 96 ++
drivers/firmware/arm_scmi/sensors.c | 73 ++
drivers/firmware/arm_scmi/shmem.c | 15 +
include/linux/scmi_protocol.h | 110 ++
13 files changed, 2345 insertions(+), 27 deletions(-)
create mode 100644 drivers/firmware/arm_scmi/notify.c
create mode 100644 drivers/firmware/arm_scmi/notify.h

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2.17.1