linux-kernel - Re: [PATCH 3/6] dt-bindings: pinctrl: Add fsl,ls1012a-pinctrl yaml file

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Message-ID: <557150a3-aef5-40e7-d656-73ca6bba5857@digi.com>
Date: Wed, 28 Aug 2024 12:51:24 +1000 (AEST)
From: David Leonard <David.Leonard@...i.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
cc: linux-arm-kernel@...ts.infradead.org, Dong Aisheng <aisheng.dong@....com>, 
    Fabio Estevam <festevam@...il.com>, Shawn Guo <shawnguo@...nel.org>, 
    Jacky Bai <ping.bai@....com>, 
    Pengutronix Kernel Team <kernel@...gutronix.de>, 
    Linus Walleij <linus.walleij@...aro.org>, Rob Herring <robh@...nel.org>, 
    Krzysztof Kozlowski <krzk+dt@...nel.org>, 
    Conor Dooley <conor+dt@...nel.org>, linux-gpio@...r.kernel.org, 
    devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] dt-bindings: pinctrl: Add fsl,ls1012a-pinctrl yaml
 file

On Wed, 28 Aug 2024, David Leonard wrote:

>> OK, but I still wonder why is it here. Without it the hardware will work
>> in little-endian?
>
> Well, it's here firstly because I was trying to follow a perceived convention 
> in
> dts/freescale/fsl,ls1012a.dtsi. That DT uses big-endian in child
> nodes of /soc that match up with memory map tables from the datasheet.
> (Not only do different and adjacent parts of the register map have
> opposing endianess, some register layouts also seem to be reversed
> bitwise, others bytewise.)
>
> The second reason is practical/dodgy. The pinctrl driver should logically
> be a child of the scfg node, but the syscon driver doesn't populate its
> child nodes. To get the pinctrl driver to work meant making it a sibling
> node with an unsatisfactory overlap with the scfg's address region
> 0x1570000+0x10000. (No driver binds to "fsl,ls1012a-scfg".)

Sorry, my examples had mixed up some ls1046a with ls1012a, which
must be confusing. Corrections follow, should the meaning have been lost:

         soc {
                 compatible = "simple-bus";
                 #address-cells = <2>;
                 #size-cells = <2>;
                 ...

                 scfg: scfg@...0000 {
                         compatible = "fsl,ls1012a-scfg", "syscon";
                         reg = <0x0 0x1570000 0x0 0x10000>;
                         big-endian;
                 };

                 pinctrl: pinctrl@...0430 {
                         compatible = "fsl,ls1012a-pinctrl";
                         reg = <0x0 0x1570430 0x0 0x4>; /* SCFG PMUXCR0 */
                         big-endian;
                         fsl,dcfg-regmap = <&dcfg>;
                         ...
                 };
         };

> The better device tree would be:

         soc {
                 compatible = "simple-bus";
                 #address-cells = <2>;
                 #size-cells = <2>;
                 ...

                 scfg: scfg@...0000 {
                         compatible = "fsl,ls1012a-scfg", "syscon";
                         reg = <0x0 0x1570000 0x0 0x10000>;
                         big-endian;
                         #address-cells = <1>;
                         #size-cells = <1>;
                         ...

                         pinctrl: pinctrl@430 {
                                 compatible = "fsl,ls1012a-pinctrl";
                                 reg = <0x430 0x4>; /* SCFG PMUXCR0 */
                                 fsl,dcfg-regmap = <&dcfg (416/8)>;
                                 ...
                         };
                 };
         };

> And this would resolve the big-endian property issue.
>
> There was a discussion of syscon populating its child nodes at
> https://lore.kernel.org/lkml/1403513950.4136.34.camel@paszta.hi.pengutronix.de/T/