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From:   Cristian Marussi <cristian.marussi@arm.com>
To:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc:     sudeep.holla@arm.com, lukasz.luba@arm.com,
        james.quinlan@broadcom.com, Jonathan.Cameron@Huawei.com,
        f.fainelli@gmail.com, etienne.carriere@linaro.org,
        thara.gopinath@linaro.org, vincent.guittot@linaro.org,
        souvik.chakravarty@arm.com, cristian.marussi@arm.com
Subject: [PATCH v4 0/37] SCMI vendor protocols and modularization
Date:   Wed,  6 Jan 2021 20:15:33 +0000
Message-Id: <20210106201610.26538-1-cristian.marussi@arm.com>
Precedence: bulk

Hi all,

The current SCMI implementation does not provide an interface to easily
develop and include a custom vendor protocol implementation as prescribed
by the SCMI standard, also because, there is not currently any custom
protocol in the upstream to justify the development of a custom interface
and its maintenance.

Moreover the current interface exposes protocol operations to the SCMI
driver users attaching per-protocol operations directly to the handle
structure, which, in this way, tends to grow indefinitely for each new
protocol addition.

Beside this, protocols private data are also exposed via handle *_priv
pointers, making such private data accessible also to the SCMI drivers
even if neither really needed nor advisable.

This series wants to address this by simplifying the SCMI protocols
interface and reducing it, roughly, to these common generic operations:

handle->devm_get_ops() / handle->devm_put_ops() / handle->notify_ops()

All protocols' private data pointers are removed from handle too and made
accessible only to the protocols code through dedicated internal helpers.

The concept of protocol handle is introduced in the SCMI protocol code
to represent a protocol instance initialized against a specific SCMI
instance (handle), so that all the new protocol code uses such protocol
handles wherever previously SCMI handle was used: this enable tighter
control of what is exposed to the protocol code vs the SCMI drivers.

Moreover protocol initialization is moved away from device probe and now
happens on demand when the first user shows up (first .get_ops), while
de-initialization is performed once the last user of the protocol (even in
terms of notifications) is gone, with the SCMI core taking care to perform
all the needed underlying resource accounting.

This way any new future standard or custom protocol implementation will
expose a common unified interface which does not need to be extended
endlessly: no need to maintain a custom interface only for vendor protos.
SCMI drivers written on top of standard or custom protocols will use this
same common interface to access any protocol operations.

All existent upstream SCMI drivers are converted to this new interface.

Patch [4/37] ("firmware: arm_scmi: introduce bare get/put protocols ops")
is marked as RFC because I was not sure if this non devres methods are
really needed (probbaly not).

In order to make this migration painless and to avoid the need of a big
un-mergeable jumbo patch touching all over the protocols and drivers (like
it was in v2), since v3 the migration process has been heavily split with a
bit of transient code added along the way (to preserve bisectability) and
finally removed towards the ends of the series.
Protocols and SCMI drivers migration to the new interface happens along
patches 11->30.

Note that in v4 all the related SCMI drivers maintainers are still NOT
CC'ed given I am still sort of gather consensus about the interface itself.

Leveraging this new centralized and common initialization flow we took
care also to refactor and simplify protocol-events registration and remove
*notify_priv from the handle interface making it accessible only to the
notification core.

Patch 36 builds on top of this new interface and introduces a mechanism to
define an SCMI protocol as a full blown module (possibly loadable) while
leaving the core dealing with proper resource accounting.
Standard protocols are still kept as builtins in this series, though.

Finally, patch 37 introduces dynamic SCMI devices creation to avoid having
to update the static module device table in the core each time a new driver
is added.

The whole SCMI stack can still be built alternatively as a module (including
all the standard protocols in scmi-module.ko in that case).

On top of this series an example SCMI Custom protocol 0x99 and related
SCMI Custom Dummy driver has been built and it is available at [1] as a
series of DEBUG patches on top this same series.

The series is currently based on for-next/scmi [2] on top of:

commit 6054d97ab512 MAINTAINERS: Update ARM SCMI entry

Any feedback welcome.

Thanks,

Cristian

---
v3 --> v4
- rebased on sudeep/for-next/scmi v5.11-rc1
- added a few comments more

v2 --> v3
- added dynamic SCMI devices creation (getting rid of static device table)
- heavy split of protocols and drivers migrations to the new interface
- rebased on top of next-20201201 so migrating also:
  + SCMIv3.0 Voltage Domain protocol & SCMI Regulator
  + SCMIv3.0 Sensor Extensions

v1 --> v2
- rebased on for-next/scmi v5.10-rc1
- introduced protocol handles
- added devres managed devm_ variant for protocols operations
- made all scmi_protocol refs const
- introduced IDR to handle protocols instead of static array
- refactored code around fast path

[1]:https://gitlab.arm.com/linux-arm/linux-cm/-/commits/scmi_modules_ext_V4/
[2]:https://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux.git/log/?h=for-next/scmi

Cristian Marussi (37):
  firmware: arm_scmi: review protocol registration interface
  firmware: arm_scmi: introduce protocol handle definitions
  firmware: arm_scmi: introduce devres get/put protocols operations
  [RFC] firmware: arm_scmi: introduce bare get/put protocols ops
  firmware: arm_scmi: make notifications aware of protocols users
  firmware: arm_scmi: introduce new devres notification ops
  firmware: arm_scmi: refactor events registration
  firmware: arm_scmi: convert events registration to protocol handles
  firmware: arm_scmi: add new protocol handle core xfer ops
  firmware: arm_scmi: add helper to access revision area memory
  firmware: arm_scmi: port Base protocol to new interface
  firmware: arm_scmi: port Perf protocol to new protocols interface
  cpufreq: scmi: port driver to the new scmi_perf_proto_ops interface
  firmware: arm_scmi: remove legacy scmi_perf_ops protocol interface
  firmware: arm_scmi: port Power protocol to new protocols interface
  firmware: arm_scmi: port GenPD driver to the new scmi_power_proto_ops
    interface
  firmware: arm_scmi: remove legacy scmi_power_ops protocol interface
  firmware: arm_scmi: port Clock protocol to new protocols interface
  clk: scmi: port driver to the new scmi_clk_proto_ops interface
  firmware: arm_scmi: remove legacy scmi_clk_ops protocol interface
  firmware: arm_scmi: port Reset protocol to new protocols interface
  reset: reset-scmi: port driver to the new scmi_reset_proto_ops
    interface
  firmware: arm_scmi: remove legacy scmi_reset_ops protocol interface
  firmware: arm_scmi: port Sensor protocol to new protocols interface
  hwmon: (scmi) port driver to the new scmi_sensor_proto_ops interface
  firmware: arm_scmi: remove legacy scmi_sensor_ops protocol interface
  firmware: arm_scmi: port SystemPower protocol to new protocols
    interface
  firmware: arm_scmi: port Voltage protocol to new protocols interface
  regulator: scmi: port driver to the new scmi_voltage_proto_ops
    interface
  firmware: arm_scmi: remove legacy scmi_voltage_ops protocol interface
  firmware: arm_scmi: make references to handle const
  firmware: arm_scmi: cleanup legacy protocol init code
  firmware: arm_scmi: cleanup unused core xfer wrappers
  firmware: arm_scmi: cleanup events registration transient code
  firmware: arm_scmi: make notify_priv really private
  firmware: arm_scmi: add protocol modularization support
  firmware: arm_scmi: add dynamic scmi devices creation

 drivers/clk/clk-scmi.c                     |  27 +-
 drivers/cpufreq/scmi-cpufreq.c             |  37 +-
 drivers/firmware/arm_scmi/base.c           | 140 ++--
 drivers/firmware/arm_scmi/bus.c            | 100 ++-
 drivers/firmware/arm_scmi/clock.c          | 129 ++--
 drivers/firmware/arm_scmi/common.h         | 117 +++-
 drivers/firmware/arm_scmi/driver.c         | 780 +++++++++++++++++++--
 drivers/firmware/arm_scmi/notify.c         | 297 ++++++--
 drivers/firmware/arm_scmi/notify.h         |  38 +-
 drivers/firmware/arm_scmi/perf.c           | 262 +++----
 drivers/firmware/arm_scmi/power.c          | 134 ++--
 drivers/firmware/arm_scmi/reset.c          | 146 ++--
 drivers/firmware/arm_scmi/scmi_pm_domain.c |  26 +-
 drivers/firmware/arm_scmi/sensors.c        | 230 +++---
 drivers/firmware/arm_scmi/system.c         |  61 +-
 drivers/firmware/arm_scmi/voltage.c        | 122 ++--
 drivers/hwmon/scmi-hwmon.c                 |  24 +-
 drivers/regulator/scmi-regulator.c         |  39 +-
 drivers/reset/reset-scmi.c                 |  33 +-
 include/linux/scmi_protocol.h              | 191 ++---
 20 files changed, 2024 insertions(+), 909 deletions(-)

-- 
2.17.1