Re: [PATCH V2 1/6] dt-bindings: pinctrl: support specifying pins, groups & functions

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On 25.11.2021 09:49, Tony Lindgren wrote:
* Rafał Miłecki <zajec5@xxxxxxxxx> [211124 23:05]:
--- a/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl.yaml
@@ -42,4 +42,44 @@ properties:
        This property can be set either globally for the pin controller or in
        child nodes for individual pin group control.
+ pins:
+    type: object
+
+    patternProperties:
+      "^.*$":
+        type: object
+
+        properties:
+          number:
+            description: Pin number
+            $ref: /schemas/types.yaml#/definitions/uint32
+
+        additionalProperties: false

Please don't introduce Linux kernel internal numbering here. It's
like bringing back the interrupt numbers again.

This is a new bit to me and the reason why I got this binding that way.

I had no idea pin numbering is system specific thing. I always thought
pin numbers are present in every chip datasheets and that is just a part
of hardware.

Now I'm reading https://www.kernel.org/doc/Documentation/pinctrl.txt
again it indeed seems to mention that numbering is handled in a way not
related to specs: "I enumerated the pins from 0 in the upper left corner
to 63 in the lower right corner.".

Sorry for that, I hopefully understand your point correctly now.


Just make this into
a proper hardware offset from the controller base, so a reg property.
Sure in some cases the reg property is just an index depending on
the controller, we don't really care from the binding point of view.

We already have #pinctrl-cells, so plase do something like the four
ximaginary examples below:

	#pinctrl-cells = <1>;
	...
	pin@foo {
		reg = <0xf00 MUX_MODE0>;
		label = "foo_pin";
	};


	#pinctrl-cells = <2>;
	...
	pin@foo {
		reg = <0xf00 PIN_INPUT_PULLUP MUX_MODE3>;
	};


	#pinctrl-cells = <2>;
	...
	pin@f00 {
		reg = <0xf00 DELAY_PS(0) DELAY_PS(0)>;
	};


	#pinctrl-cells = <3>;
	...
	pin@f00 {
		reg = <0xf00 MUX_MODE3 PULL_UP_STRENGTH(36) PULL_DOWN_STRENGTH(20)>;
	};


Then let's attempt to use just standard numbers and defines for the
values where possible. Then a group of pins is just a list of the pin
phandles in the devicetree.

I need to ask for help on understanding that reg = <...> syntax.

(Why) do we need to put that extra info in a "reg" property? That seems
like either:
1. Pin specific info
or
2. Phandle arguments

In the first case, instead of:
	pin@f00 {
		reg = <0xf00 MUX_MODE3 PULL_UP_STRENGTH(36) PULL_DOWN_STRENGTH(20)>;
	};
I'd rather use:
	pin@f00 {
		reg = <0xf00>;
		mux_mode3;
		pull_up_strength = <36>;
		pull_down_strength = <20>;
	};

In the second case, shouldn't that be something like:
	pins {
		bar: pin@f00 {
			reg = <0xf00>;
			#pinctrl-cells = <3>;
		};
	};

	groups {
		qux {
			pins = <&bar MUX_MODE3 PULL_UP_STRENGTH(36) PULL_DOWN_STRENGTH(20)>;
		}
	};



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