linux-kernel - Re: [RFC} arm architecture board/feature deprecation timeline

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Message-Id: <a8c009b5-ada0-4f78-92f7-7a6c5075ccf1@app.fastmail.com>
Date: Mon, 19 Aug 2024 16:12:10 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Jeremy J. Peper" <jeremy@...emypeper.com>,
 linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, "Russell King" <linux@...linux.org.uk>,
 "Linus Walleij" <linus.walleij@...aro.org>,
 "Richard Earnshaw" <richard.earnshaw@....com>,
 "Richard Sandiford" <richard.sandiford@....com>,
 "Ramana Radhakrishnan" <ramanara@...dia.com>,
 "Nicolas Pitre" <nico@...xnic.net>,
 "Krzysztof Kozlowski" <krzk@...nel.org>,
 "Mark Brown" <broonie@...nel.org>,
 "Kristoffer Ericson" <kristoffer.ericson@...il.com>,
 "Robert Jarzmik" <robert.jarzmik@...e.fr>,
 "Aaro Koskinen" <aaro.koskinen@....fi>,
 "Janusz Krzysztofik" <jmkrzyszt@...il.com>,
 "Tony Lindgren" <tony@...mide.com>,
 Linux-OMAP <linux-omap@...r.kernel.org>,
 "Nikita Shubin" <nikita.shubin@...uefel.me>,
 linux-samsung-soc@...r.kernel.org, "Andrew Lunn" <andrew@...n.ch>,
 "Sebastian Hesselbarth" <sebastian.hesselbarth@...il.com>,
 "Gregory Clement" <gregory.clement@...tlin.com>,
 debian-arm@...ts.debian.org,
 "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
 "Alexandre Torgue" <alexandre.torgue@...s.st.com>
Subject: Re: [RFC} arm architecture board/feature deprecation timeline

Two small additions:

On Mon, Aug 19, 2024, at 11:17, Arnd Bergmann wrote:
> On Thu, Aug 15, 2024, at 21:53, jeremy@...emypeper.com wrote:
> I expect that the terastation pro2 is going to be fairly easy to
> convert to DT as there is already support for similar Orion5x
> machines. In this case I would just remove all the Orion5x board
> files and you can add a dts file later on. The bit I'm unsure
> about here is legacy PCI support. I see that the board file enables
> both PCI and PCIe, but I don't know if both are actually used,
> or if everything is on PCIe.
>
> I have some old patches for separating orion legacy PCI from
> PCIe support, as only the latter has a modern driver (shared
> with kirkwood and armadaxp). If you can confirm that the machine
> actually uses PCI, I can dig those out from my backups.

I did find this myself later, the machine does use an on-board
PCI connected SATA controller, which is obviously required to
make the machine useful.

Doing a PCI host bridge driver with DT support correctly is
a lot of work, especially if there is only a single machine
using it. Since this uses the same drivers/ata/sata-mv.c
driver as the other orion/kirkwood machines, I wonder if we
can just pretend that this is a platform device and skip
all of the PCI probing. I think this only needs a few
small changes to the sata-mv.c driver, but it does require
that the PCI bus is left in a known state by the boot loader.

> The WXL machine is going to be more work since there is currently
> no DT support for mv78xx0, but everything except the pin controller
> should at least have a driver since this SoC is somewhere between
> Kirkwood and Dove. Having a hack for the pin controller similar
> to what orion5x has is probably fine, especially if you only
> need to support one machine.

The complication here is that removing the board file would
imply that all of the mv78xx0 code immediately becomes dead
code. I guess the next best idea is to remove the orion5x
and dove board files first and then move bits of plat-orion
that are actually used by the WXL machine into the mv78xx0
directory.

      Arnd