[RFC,v6,0/6] Exynos: Simple QoS for exynos-bus using interconnect

Message

Sylwester Nawrocki/Kernel \(PLT\) /SRPOL/Staff Engineer/Samsung Electronics July 2, 2020, 4:37 p.m. UTC

This patchset adds interconnect API support for the Exynos SoC "samsung,
exynos-bus" compatible devices, which already have their corresponding
exynos-bus driver in the devfreq subsystem.  Complementing the devfreq
driver with an interconnect functionality allows to ensure the QoS
requirements of devices accessing the system memory (e.g. video processing
devices) are fulfilled and aallows to avoid issues like the one discussed
in thread [1].

This patch series adds implementation of the interconnect provider per each
"samsung,exynos-bus" compatible DT node, with one interconnect node per
provider.  The interconnect code which was previously added as a part of
the devfreq driver has been converted to a separate platform driver.
In the devfreq a corresponding virtual child platform device is registered.
Integration of devfreq and interconnect frameworks is achieved through
the PM QoS API.

A sample interconnect consumer for exynos-mixer is added in patches 5/6,
6/6, it is currently added only for exynos4412 and allows to address the
mixer DMA underrun error issues [1].

Main changes since v5 [3] is an addition of "bus-width: DT property, which
specifies data width of the interconnect bus (patches 1...2/6 and addition
of synchronization of the interconnect bandwidth setting with VSYNC
(patch 6/6).

The series has been tested on Odroid U3 board. It is based on icc-next
branch, which already includes required patches [2]:
 26c205e interconnect: Allow inter-provider pairs to be configured
 0db4ee05 interconnect: Relax requirement in of_icc_get_from_provider()
 6998a7c interconnect: Export of_icc_get_from_provider()

--
Regards,
Sylwester


Changes since v3 [4] (v4 skipped to align with patchset [1]), detailed
changes are listed in each patch:
 - conversion to a separate interconnect (platform) driver,
 - an update of the DT binding documenting new optional properties:
   #interconnect-cells, samsung,interconnect-parent in "samsung,exynos-bus"
   nodes,
 - new DT properties added to the SoC, rather than to the board specific
   files.

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 [6]:
 - 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.


References:
[1] https://patchwork.kernel.org/patch/10861757/ (original issue)
[2] https://www.spinics.net/lists/linux-samsung-soc/msg70014.html
[3] https://www.spinics.net/lists/arm-kernel/msg810722.html
[4] https://lore.kernel.org/linux-pm/[e-mail]
[5] https://patchwork.kernel.org/cover/11054417/ (v1 of this RFC)
[6] https://patchwork.kernel.org/cover/11152595/ (v2 of this RFC)


Artur Świgoń (1):
  ARM: dts: exynos: Add interconnects to Exynos4412 mixer

Sylwester Nawrocki (5):
  dt-bindings: exynos-bus: Add documentation for interconnect properties
  interconnect: Add generic interconnect driver for Exynos SoCs
  PM / devfreq: exynos-bus: Add registration of interconnect child
    device
  ARM: dts: exynos: Add interconnect properties to Exynos4412 bus nodes
  drm: exynos: mixer: Add interconnect support

 .../devicetree/bindings/devfreq/exynos-bus.txt     |  68 +++++++-
 arch/arm/boot/dts/exynos4412.dtsi                  |   7 +
 drivers/devfreq/exynos-bus.c                       |  17 ++
 drivers/gpu/drm/exynos/exynos_mixer.c              | 150 +++++++++++++++-
 drivers/interconnect/Kconfig                       |   1 +
 drivers/interconnect/Makefile                      |   1 +
 drivers/interconnect/exynos/Kconfig                |   6 +
 drivers/interconnect/exynos/Makefile               |   4 +
 drivers/interconnect/exynos/exynos.c               | 192 +++++++++++++++++++++
 9 files changed, 436 insertions(+), 10 deletions(-)
 create mode 100644 drivers/interconnect/exynos/Kconfig
 create mode 100644 drivers/interconnect/exynos/Makefile
 create mode 100644 drivers/interconnect/exynos/exynos.c

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2.7.4