linux-kernel - Re: [PATCH] spi: mt7621: allow GPIO chip select lines

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Message-ID: <6c92fddd-f79b-40b5-bd52-61f43d6a7591@sirena.org.uk>
Date: Fri, 15 Mar 2024 17:47:17 +0000
From: Mark Brown <broonie@...nel.org>
To: Justin Swartz <justin.swartz@...ingedge.co.za>
Cc: Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] spi: mt7621: allow GPIO chip select lines

On Fri, Mar 15, 2024 at 06:23:09PM +0200, Justin Swartz wrote:
> On 2024-03-15 16:45, Mark Brown wrote:

> > The core should handle GPIO chip selects for you?

> As far as I can tell, it doesn't - at least as far the state
> of spi-mt7621.c is concerned prior to the patch, plus kernel
> configuration choices, device tree definition, and other
> factors I might not be taking into account.

> But maybe I'm doing something wrong, or perhaps have a
> misconfiguration somewhere. So, if you're able to point out
> something I've done incorrectly, it would be appreciated.

Look at other drivers that support GPIO chip selects?

> To attempt to confirm if the core will handle my desired
> GPIO chip select lines without explicit state toggling,
> I tried to set the value of use_gpio_descriptors to true,
> without any other modifications to spi-mt7621.c as of
> commit 90d35da658da8cff0d4ecbb5113f5fac9d00eb72:

Please include human readable descriptions of things like commits and
issues being discussed in e-mail in your mails, this makes them much
easier for humans to read especially when they have no internet access.
I do frequently catch up on my mail on flights or while otherwise
travelling so this is even more pressing for me than just being about
making things a bit easier to read.

The core needs to know that the GPIO chip selects are there but once it
knows that they're there things like setting the chip select should just
work.

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