linux-kernel - Re: [PATCH v4 2/2] ARM: dts: am33xx-l4: change #pinctrl-cells from 1 to 2

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Date:   Tue, 08 Sep 2020 17:34:53 -0700
From:   Trent Piepho <tpiepho@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Drew Fustini <drew@...gleboard.org>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        devicetree@...r.kernel.org,
        "bcousson@...libre.comLinus Walleij" <linus.walleij@...aro.org>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v4 2/2] ARM: dts: am33xx-l4: change #pinctrl-cells from 1 to 2

On Tuesday, June 30, 2020 6:33:20 PM PDT Drew Fustini wrote:
> Increase #pinctrl-cells to 2 so that mux and conf be kept separate. This
> requires the AM33XX_PADCONF macro in omap.h to also be modified to keep pin
> conf and pin mux values separate.

> --- a/arch/arm/boot/dts/am33xx-l4.dtsi
> +++ b/arch/arm/boot/dts/am33xx-l4.dtsi
> @@ -278,7 +278,7 @@ scm: scm@0 {
>  				am33xx_pinmux: pinmux@800 {
>  					compatible = "pinctrl-single";
>  					reg = <0x800 0x238>;
> -					#pinctrl-cells = <1>;
> +					#pinctrl-cells = <2>;

>  #define AM33XX_IOPAD(pa, val)		OMAP_IOPAD_OFFSET((pa), 0x0800) (val)
> -#define AM33XX_PADCONF(pa, dir, mux)	OMAP_IOPAD_OFFSET((pa), 0x0800) ((dir) | (mux))
> +#define AM33XX_PADCONF(pa, conf, mux)	OMAP_IOPAD_OFFSET((pa), 0x0800) (conf) (mux)

If a dts file uses am33xx_pinmux from am33xx-l4.dtsi, but does not use the
AM33XX_PADCONF() macro for all pin settings, like say it uses AM33XX_IOPAD(),
then the dtb will be totally broken as pin addresses and values will all be
off.

Similarly, using AM33XX_PADCONF() with a different pinctrl defined elsewhere
would also break.

In the latest linux-next kernel, I found one case of the former problem, in
am335x-guardian.dts.

The barebox bootloader had all the am33xx boards broken when the dts change
was imported without adding the OR-two-values special case to the pinctrl
driver.  Which I then tracked to here.