linux-kernel - Re: [PATCH] pinctrl-mcp23s08: Reset all pins to input at probe

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Message-ID: <CACRpkdYLDLM603DHJvkMbDRo8pVZZfB6DT+ck4070zVAB4SCBQ@mail.gmail.com>
Date: Tue, 15 Apr 2025 09:21:42 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Mike Looijmans <mike.looijmans@...ic.nl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Dmitry Mastykin <mastichi@...il.com>, Evgenii Shatokhin <e.shatokhin@...ro.com>, 
	Arturas Moskvinas <arturas.moskvinas@...il.com>, Andreas Kaessens <akaessens@...il.com>, 
	Radim Pavlik <radim.pavlik@...-biometrics.com>, 
	Thomas Preston <thomas.preston@...ethink.co.uk>
Subject: Re: [PATCH] pinctrl-mcp23s08: Reset all pins to input at probe

On Fri, Mar 14, 2025 at 4:18 PM Mike Looijmans <mike.looijmans@...ic.nl> wrote:


> At startup, the driver just assumes that all registers have their
> default values. But after a soft reset, the chip will just be in the
> state it was, and some pins may have been configured as outputs. Any
> modification of the output register will cause these pins to be driven
> low, which leads to unexpected/unwanted effects. To prevent this from
> happening, set the chip's IO configuration register to a known safe
> mode (all inputs) before toggling any other bits.
>
> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>

Patch tentatively applied for v6.16.

CC to some mcp23s08 users so they can check it out.

Yours,
Linus Walleij