[RFC PATCH v3 0/7] PM / devfreq: Simple QoS for exynos-bus using interconnect

[Artur Świgoń]

The following patchset adds interconnect[1][2] framework support to the
exynos-bus devfreq driver. Extending the devfreq driver with
interconnect functionality started as a response to the issue referenced
in [3]. The patches can be subdivided into three groups:

(a) Tweaking the interconnect framework to support the exynos-bus use
case (patches 01--03/07). Exporting of_icc_get_from_provider() allows to
avoid hardcoding every single graph edge in the DT or driver source, and
relaxing the requirement on #interconnect-cells removes the need to
provide dummy node IDs in the DT. A new field in struct icc_provider is
used to explicitly allow configuring node pairs from two different
providers.

(b) Implementing interconnect providers in the exynos-bus devfreq driver
and adding required DT properties for one selected platform, namely
Exynos4412 (patches 04--05/07). Due to the fact that this aims to be a
generic driver for various Exynos SoCs, node IDs are generated
dynamically (rather than hardcoded).

(c) Implementing a sample interconnect consumer for exynos-mixer
targeted at solving the issue referenced in [3], again with DT
properties only for Exynos4412 (patches 06--07/07).

Integration of devfreq and interconnect frameworks is achieved by using
the dev_pm_qos_*() API. When CONFIG_INTERCONNECT is 'n' (such as in
exynos_defconfig) all interconnect API functions are no-ops.

This series depends on these three patches (merged into devfreq-next[6]):
* https://patchwork.kernel.org/patch/11279087/
* https://patchwork.kernel.org/patch/11279093/
* https://patchwork.kernel.org/patch/11293765/
and on this series:
* https://patchwork.kernel.org/cover/11304545/
(which does not apply cleanly on next-20191220, adding
--exclude=arch/arm/boot/dts/exynos5422-odroid-core.dtsi to 'git am' is a
quick workaround)

---
Changes since v2 [5]:
* Use icc_std_aggregate().
* Implement a different modification of apply_constraints() in
  drivers/interconnect/core.c (patch 03).
* Use 'exynos,interconnect-parent-node' in the DT instead of
  'devfreq'/'parent', depending on the bus.
* Rebase on DT patches that deprecate the 'devfreq' DT property.
* Improve error handling, including freeing generated IDs on failure.
* Remove exynos_bus_icc_connect() and add exynos_bus_icc_get_parent().

---
Changes since v1 [4]:
* Rebase on coupled regulators patches.
* Use dev_pm_qos_*() API instead of overriding frequency in
  exynos_bus_target().
* Use IDR for node ID allocation.
* Reverse order of multiplication and division in
  mixer_set_memory_bandwidth() (patch 07) to avoid integer overflow.

---
Artur Świgoń
Samsung R&D Institute Poland
Samsung Electronics

---
References:
[1] Documentation/interconnect/interconnect.rst
[2] Documentation/devicetree/bindings/interconnect/interconnect.txt
[3] https://patchwork.kernel.org/patch/10861757/ (original issue)
[4] https://patchwork.kernel.org/cover/11054417/ (v1 of this RFC)
[5] https://patchwork.kernel.org/cover/11152595/ (v2 of this RFC)
[6] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/log/?h=devfreq-next

Artur Świgoń (6):
  interconnect: Export of_icc_get_from_provider()
  interconnect: Relax requirement in of_icc_get_from_provider()
  interconnect: Allow inter-provider pairs to be configured
  arm: dts: exynos: Add interconnect bindings for Exynos4412
  devfreq: exynos-bus: Add interconnect functionality to exynos-bus
  arm: dts: exynos: Add interconnects to Exynos4412 mixer

Marek Szyprowski (1):
  drm: exynos: mixer: Add interconnect support

 .../boot/dts/exynos4412-odroid-common.dtsi    |   5 +
 arch/arm/boot/dts/exynos4412.dtsi             |   1 +
 drivers/devfreq/exynos-bus.c                  | 144 ++++++++++++++++++
 drivers/gpu/drm/exynos/exynos_mixer.c         |  71 ++++++++-
 drivers/interconnect/core.c                   |  16 +-
 include/linux/interconnect-provider.h         |   8 +
 6 files changed, 232 insertions(+), 13 deletions(-)

--
2.17.1