linux-kernel - Re: [PATCH 0/4] Driver for Apple Z2 touchscreens.

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Message-ID: <CAMT+MTThJoYLYhtYAHwh6F3LTApid9Em+eP2AZYc3JChC2b9ig@mail.gmail.com>
Date: Wed, 27 Nov 2024 09:29:19 +0100
From: Sasha Finkelstein <fnkl.kernel@...il.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>, 
	Alyssa Rosenzweig <alyssa@...enzweig.io>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Henrik Rydberg <rydberg@...math.org>, asahi@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-input@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Janne Grunau <j@...nau.net>, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 0/4] Driver for Apple Z2 touchscreens.

On Wed, 27 Nov 2024 at 02:51, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> I believe this needs to be done at the SPI controller level. See
> "cs-gpiods" property in
> Documentation/devicetree/bindings/spi/spi-controller.yaml that, as far
> as I understand, allows overriding controller's native CS handling with
> a GPIO when needed.

I have already tried doing that (adding the relevant gpio as cs-gpios
on the controller)
and for some reason none of my attempts worked. Since there is no hardware
documentation, I can't really tell why, could be possible that we need both
native CS and that gpio, could be memory barrier issues somewhere in
the driver core,
but the method above is the only one i could get to work.