linux-kernel - Re: [PATCH v7 16/16] pinctrl: qcom: make the pinmuxing strict

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Message-ID: <8a54bbbd-2b7a-482f-9ab5-eac83264b1f6@sirena.org.uk>
Date: Wed, 3 Sep 2025 12:06:55 +0100
From: Mark Brown <broonie@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
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	Andy Shevchenko <andy@...nel.org>,
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	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
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	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v7 16/16] pinctrl: qcom: make the pinmuxing strict

On Wed, Sep 03, 2025 at 01:53:00PM +0300, Andy Shevchenko wrote:

> (Not sure, but SPI DesignWare requires programming SPI native chip selects even
>  if the GPIO is used for that, this might have also some implications, but here
>  it's for real 'purely speculative'.)

It is very common for SPI controllers to absolutely require setting a
chip select in order to do a transfer, when using GPIO chip selects with
such controllers the standard practice is to just not mux out the chip
select signal from the controller and do everything in software.  The IP
will be doing it's thing with it's chip select signal but that signal is
never actually connected to anything.

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