linux-kernel - Re: [PATCH 00/10] ARM: pxa: use software nodes/properties for GPIOs

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Date: Fri, 28 Jun 2024 22:59:53 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
 "Haojian Zhuang" <haojian.zhuang@...il.com>,
 "Daniel Mack" <daniel@...que.org>, "Robert Jarzmik" <robert.jarzmik@...e.fr>,
 "Linus Walleij" <linus.walleij@...aro.org>, soc@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] ARM: pxa: use software nodes/properties for GPIOs

On Fri, Jun 28, 2024, at 20:08, Dmitry Torokhov wrote:
> This series converts legacy pxa boards (spitz, gumstix) to use software
> nodes/properties to describe various GPIOs instead of relying on GPIO
> lookup tables. The benefit is that structure and behavior is closer to
> DT-described GPIOs.
>
> The very first patch ("ARM: spitz: fix GPIO assignment for backlight")
> is actually a fix that IMO should be applied sooner rather than later,
> the rest of patches are enhancements. The reason it is sent with the
> rest of the series is that later changes contextually depend on it.
>
> The last patch ("ARM: spitz: Use software nodes for the ADS7846
> touchscreen") soft-depends on corresponding changes by Linus Walleij to
> the ads7846 driver in input tree. It compiles without it, but the device
> will not sync with display refreshes. I have created an immutable branch
> (branched from v6.9) at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git ib/ads7846-hsync
>
> in case you wish to pull it in.
>
> Regretfully it was only compiled as I do not have access to the relevant
> hardware.

Hi Dmitry,

I'm happy to pull these in directly, hopefully with some extra
review or ack from the maintainers. If there are no negative
comments, feel free to resend them to soc@...nel.org for me
to pick up.

Is your goal to of the series to eventually convert all
gpio descriptors over to software nodes, or are you working
towards converting all of mach-pxa to DT?

In the latter case, note that the reason we kept these
specific board files is that they have reasonable support in
qemu and you can probably figure out how to test them if you
try hard enough. I have not tried myself though, and there is
a high chance that current kernels won't boot without extra
fixes.

If your goal is to change all board files to software nodes,
I think we should take a step back, since most of those boards
are likely to get removed anyway. Two years ago, I removed
almost 90% of the board files remaining at the time after
showing that they were pretty much all unused. I kept the
ones that either had known users, or that someone wanted to
keep for some reason and work on doing the DT conversion.
For most of these (including PXA), there has been no work
on this in the past two years, so I think we should ask the
same question again and see which ones we can just remove
this time.

      Arnd