linux-kernel - Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

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Date:   Thu, 18 Mar 2021 20:40:42 +0100
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Drew Fustini <drew@...gleboard.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>,
        Joe Perches <joe@...ches.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH v9 2/4] pinctrl: pinmux: Add pinmux-select debugfs file

On 13.03.21 19:47, Geert Uytterhoeven wrote:

>>> I've already been playing with similar idea, but for external muxes.
>>> For example, some boards have multiple SIM slots that can be switched
>>> via some gpio pin.
>>>
>>> Not sure whether traditional pinmux would be a good match for that.
>>
>> If you want to be able to use both, then I guess gpio-mux is what you
>> are looking for. Obviously, it will also require support in the bus
>> core. On what bus are those SIMs? (I guess the answer will be UART and
>> then unfortunately UARTs are not represented as busses).
> 
> We do have support for devices connected to UARTs.
> See patternProperties in Documentation/devicetree/bindings/serial/serial.yaml.
> Or do you mean something different?

in my case, the SIM cards are connected directly to the baseband
(there're extra lines on the m2 slots for that). CPU doesn't ever see
any of this traffic, just can select which SIM card is routed to the
m2 slot via gpio.


--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287