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    Subject[RFC PATCH v2 00/11] Simple QoS for exynos-bus driver using interconnect
    Date
    The following patchset adds interconnect[1][2] framework support to the
    exynos-bus devfreq driver. Extending the devfreq driver with interconnect
    capabilities started as a response to the issue referenced in [3]. The
    patches can be subdivided into four logical groups:

    (a) Refactoring the existing devfreq driver in order to improve readability
    and accommodate for adding new code (patches 01--04/11).

    (b) Tweaking the interconnect framework to support the exynos-bus use case
    (patches 05--07/11). Exporting of_icc_get_from_provider() allows us to
    avoid hardcoding every single graph edge in the DT or driver source, and
    relaxing the requirement contained in that function removes the need to
    provide dummy node IDs in the DT. Adjusting the logic in
    apply_constraints() (drivers/interconnect/core.c) accounts for the fact
    that every bus is a separate entity and therefore a separate interconnect
    provider, albeit constituting a part of a larger hierarchy.

    (c) Implementing interconnect providers in the exynos-bus devfreq driver
    and adding required DT properties for one selected platform, namely
    Exynos4412 (patches 08--09/11). Due to the fact that this aims to be a
    generic driver for various Exynos SoCs, node IDs are generated dynamically
    rather than hardcoded. This has been determined to be a simpler approach,
    but depends on changes described in (b).

    (d) Implementing a sample interconnect consumer for exynos-mixer targeted
    at the issue referenced in [3], again with DT info only for Exynos4412
    (patches 10--11/11).

    Integration of devfreq and interconnect functionalities is achieved by
    using dev_pm_qos_*() API[5]. All new code works equally well when
    CONFIG_INTERCONNECT is 'n' (as in exynos_defconfig) in which case all
    interconnect API functions are no-ops.

    This patchset depends on [5].

    --- Changes since v1 [6]:
    * Rebase on [4] (coupled regulators).
    * Rebase on [5] (dev_pm_qos for devfreq).
    * Use dev_pm_qos_*() API[5] instead of overriding frequency in
    exynos_bus_target().
    * Use IDR for node ID allocation.
    * Avoid goto in functions extracted in patches 01 & 02 (cf. patch 04).
    * Reverse order of multiplication and division in
    mixer_set_memory_bandwidth() (patch 11) 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/11083663/ (coupled regulators; merged)
    [5] https://patchwork.kernel.org/cover/11149497/ (dev_pm_qos for devfreq)
    [6] https://patchwork.kernel.org/cover/11054417/ (v1 of this RFC)

    Artur Świgoń (10):
    devfreq: exynos-bus: Extract exynos_bus_profile_init()
    devfreq: exynos-bus: Extract exynos_bus_profile_init_passive()
    devfreq: exynos-bus: Change goto-based logic to if-else logic
    devfreq: exynos-bus: Clean up code
    interconnect: Export of_icc_get_from_provider()
    interconnect: Relax requirement in of_icc_get_from_provider()
    interconnect: Relax condition in apply_constraints()
    arm: dts: exynos: Add parents and #interconnect-cells to 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 | 1 +
    arch/arm/boot/dts/exynos4412.dtsi | 10 +
    drivers/devfreq/exynos-bus.c | 319 +++++++++++++-----
    drivers/gpu/drm/exynos/exynos_mixer.c | 71 +++-
    drivers/interconnect/core.c | 12 +-
    include/linux/interconnect-provider.h | 6 +
    6 files changed, 327 insertions(+), 92 deletions(-)

    --
    2.17.1

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