linux-kernel - Re: [RFC PATCH v5 0/6] Exynos: Simple QoS for exynos-bus using interconnect

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Date:   Mon, 1 Jun 2020 10:17:14 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     georgi.djakov@...aro.org, cw00.choi@...sung.com, krzk@...nel.org
Cc:     a.swigon@...sung.com, myungjoo.ham@...sung.com,
        inki.dae@...sung.com, sw0312.kim@...sung.com,
        b.zolnierkie@...sung.com, m.szyprowski@...sung.com,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [RFC PATCH v5 0/6] Exynos: Simple QoS for exynos-bus using
 interconnect

Cc: Rob, devicetree ML

On 29.05.2020 18:31, Sylwester Nawrocki wrote:
> 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 to avoid issues like the one discussed in thread [1].
> 
> This patch series depends on 3 patches from Artur for the interconnect API 
> [2], which introduce following changes:
> 
>  - exporting of_icc_get_from_provider() to avoid hard coding every graph 
>    edge in the DT or driver source,
>  - relaxing the requirement on #interconnect-cells, so there is no need 
>    to provide dummy node IDs in the DT, 
>  - adding new field in struct icc_provider to explicitly allow configuring 
>    node pairs from two different providers.
> 
> This series adds implementation of 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].
> 
> The series has been tested on Odroid U3 board. It is based on icc-next 
> branch with devfreq-next branch merged and patches [2] applied.
> 
> --
> Regards,
> Sylwester
> 
> --
> Changes since v3 [3] (v4 skipped to align with patchset [1]), detailed 
> changes are listed at 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 [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.
> 
> 
> References:
> [1] https://patchwork.kernel.org/patch/10861757/ (original issue)
> [2] https://www.spinics.net/lists/linux-samsung-soc/msg70014.html
> [3] https://lore.kernel.org/linux-pm/20191220115653.6487-1-a.swigon@samsung.com
> [4] https://patchwork.kernel.org/cover/11054417/ (v1 of this RFC)
> [5] https://patchwork.kernel.org/cover/11152595/ (v2 of this RFC)
> 
> 
> Artur Świgoń (1):
>   ARM: dts: exynos: Add interconnects to Exynos4412 mixer
> 
> Marek Szyprowski (1):
>   drm: exynos: mixer: Add interconnect support
> 
> Sylwester Nawrocki (4):
>   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
> 
>  .../devicetree/bindings/devfreq/exynos-bus.txt     |  15 +-
>  arch/arm/boot/dts/exynos4412.dtsi                  |   6 +
>  drivers/devfreq/exynos-bus.c                       |  17 ++
>  drivers/gpu/drm/exynos/exynos_mixer.c              |  73 +++++++-
>  drivers/interconnect/Kconfig                       |   1 +
>  drivers/interconnect/Makefile                      |   1 +
>  drivers/interconnect/exynos/Kconfig                |   6 +
>  drivers/interconnect/exynos/Makefile               |   4 +
>  drivers/interconnect/exynos/exynos.c               | 185 +++++++++++++++++++++
>  9 files changed, 301 insertions(+), 7 deletions(-)
>  create mode 100644 drivers/interconnect/exynos/Kconfig
>  create mode 100644 drivers/interconnect/exynos/Makefile
>  create mode 100644 drivers/interconnect/exynos/exynos.c