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    SubjectRe: [net-next: PATCH 00/12] ACPI support for DSA
    On Mon, Jun 20, 2022 at 05:02:13PM +0200, Marcin Wojtas wrote:
    > Hi!
    >
    > This patchset introduces the support for DSA in ACPI world. A couple of
    > words about the background and motivation behind those changes:
    >
    > The DSA code is strictly dependent on the Device Tree and Open Firmware
    > (of_*) interface, both in the drivers and the common high-level net/dsa API.
    > The only alternative is to pass the information about the topology via
    > platform data - a legacy approach used by older systems that compiled the
    > board description into the kernel.
    >
    > The above constraint is problematic for the embedded devices based e.g. on
    > x86_64 SoCs, which are described by ACPI tables - to use DSA, some tricks
    > and workarounds have to be applied. Addition of switch description to
    > DSDT/SSDT tables would help to solve many similar cases and use unmodified
    > kernel modules. It also enables this feature for ARM64 ACPI users.
    >
    > The key enablements allowing for adding ACPI support for DSA in Linux were
    > NIC drivers, MDIO, PHY, and phylink modifications – the latter three merged
    > in 2021. I thought it would be worth to experiment with DSA, which seemed
    > to be a natural follow-up challenge.
    >
    > It turned out that without much hassle it is possible to describe
    > DSA-compliant switches as child devices of the MDIO busses, which are
    > responsible for their enumeration based on the standard _ADR fields and
    > description in _DSD objects under 'device properties' UUID [1].
    > The vast majority of required changes were simple of_* to fwnode_*
    > transition, as the DT and ACPI topolgies are analogous, except for
    > 'ports' and 'mdio' subnodes naming, as they don't conform ACPI
    > namespace constraints [2].

    ...

    > Note that for now cascade topology remains unsupported in ACPI world
    > (based on "dsa" label and "link" property values). It seems to be feasible,
    > but would extend this patchset due to necessity of of_phandle_iterator
    > migration to fwnode_. Leave it as a possible future step.

    Wondering if this can be done using fwnode graph.

    --
    With Best Regards,
    Andy Shevchenko


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