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 > >> 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. -- Florian
