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
