On Tue, Jul 28, 2020 at 11:56 PM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > On 7/28/2020 1:45 PM, Andrew Lunn wrote: > > On Tue, Jul 28, 2020 at 06:06:26PM +1000, Dan Callaghan wrote: > >> Excerpts from Andrew Lunn's message of 2020-07-24 21:14:36 +02:00: > >>> Now i could be wrong, but are Ethernet switches something you expect > >>> to see on ACPI/SBSA platforms? Or is this a legitimate use of the > >>> escape hatch? > >> > >> As an extra data point: right now I am working on an x86 embedded > >> appliance (ACPI not Device Tree) with 3x integrated Marvell switches. > >> I have been watching this patch series with great interest, because > >> right now there is no way for me to configure a complex switch topology > >> in DSA without Device Tree. > >> > >> For the device I am working on, we will have units shipping before these > >> questions about how to represent Ethernet switches in ACPI can be > >> resolved. So realistically, we will have to actually configure the > >> switches using software_node structures supplied by an out-of-tree > >> platform driver, or some hackery like that, rather than configuring them > >> through ACPI. > > > > Hi Dan > > > > I also have an x86 platform, but with a single switch. For that, i > > have a platform driver, which instantiates a bit banging MDIO bus, and > > sets up the switch using platform data. This works, but it is limited > > to internal Copper only PHYs. > > At some point I had a dsa2_platform_data implementation which was > intended to describe more complex switch set-ups and trees, the old code > is still there for your entertainment: > > https://github.com/ffainelli/linux/commits/dsa-pdata Platform data in the modern kernel is definitely the wrong approach. Software nodes of firmware nodes can be much more appreciated. > >> An approach I have been toying with is to port all of DSA to use the > >> fwnode_handle abstraction instead of Device Tree nodes, but that is > >> obviously a large task, and frankly I was not sure whether such a patch > >> series would be welcomed. > > > > I would actually suggest you look at using DT. We are struggling to > > get ACPI maintainers involved with really simple things, like the ACPI > > equivalent of a phandle from the MAC to the PHY. A full DSA binding > > for Marvell switches is pretty complex, especially if you need SFP > > support. I expect the ACPI maintainers will actively run away > > screaming when you make your proposal. > > > > DT can be used on x86, and i suspect it is a much easier path of least > > resistance. > > And you can easily overlay Device Tree to an existing system by using > either a full Device Tree overlay (dtbo) or using CONFIG_OF_DYNAMIC and > creating nodes on the fly. Why do you need DT on a system that runs without it and Linux has all means to extend to cover a lot of stuff DT provides for other types of firmware nodes? -- With Best Regards, Andy Shevchenko
