[PATCH RFC 1/2] dt-bindings: pinctrl: Add pinctrl-packed

[Billy Tsai <billy_tsai@aspeedtech.com>]

Add a Devicetree binding for a generic pin controller where pinmux and/or
pin configuration are represented as fixed-width fields packed
sequentially within shared registers.

The binding targets controllers that are typically exposed as subnodes of
a syscon node and accessed via regmap-mmio through the parent.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 .../bindings/pinctrl/pinctrl-packed.yaml           | 166 +++++++++++++++++++++
 1 file changed, 166 insertions(+)

diff --git a/Documentation/devicetree/bindings/pinctrl/pinctrl-packed.yaml b/Documentation/devicetree/bindings/pinctrl/pinctrl-packed.yaml
new file mode 100644
index 000000000000..dd01ba2fed71
--- /dev/null
+++ b/Documentation/devicetree/bindings/pinctrl/pinctrl-packed.yaml
@@ -0,0 +1,166 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pinctrl/pinctrl-packed.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic Pin Controller with Packed-Field Registers
+
+maintainers:
+  - Billy Tsai <billy_tsai@aspeedtech.com>
+
+description:
+  This binding describes pin controller hardware where pinmux and/or
+  pin configuration fields are represented as fixed-width fields packed
+  sequentially within shared registers.
+
+  Such controllers are commonly embedded within a larger system control
+  unit (SCU) register block and may be exposed as subnodes of a syscon
+  device.
+
+  Conceptually, this model is related to the pinctrl-single binding,
+  but instead of describing individual register offsets via
+  <offset, value, mask> tuples, the hardware provides fixed-width,
+  per-pin fields packed linearly within shared registers.
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - pinctrl-packed
+          - pinconf-packed
+
+  reg:
+    maxItems: 1
+
+  '#pinctrl-cells':
+    description:
+      The pinctrl provider uses standard state nodes referenced by pinctrl-N
+      properties; consumers do not pass per-pin arguments via phandle.
+    const: 1
+
+  pinctrl-packed,function-mask:
+    description: Mask of the allowed register bits for a single pin.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+  pinctrl-packed,gpio-range:
+    description: Optional list of pin base, nr pins & gpio function.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      items:
+        - description: phandle of a gpio-range node
+        - description: pin base
+        - description: number of pins
+        - description: gpio function
+
+patternProperties:
+  '-pins(-[0-9]+)?$|-pin$':
+    type: object
+    additionalProperties: false
+
+    properties:
+      pinctrl-packed,pins:
+        description: Array of pin index and function selector pairs.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+
+      pinctrl-packed,bias-pullup:
+        description: Optional bias pull-up configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 4
+        items:
+          - description: Input value.
+          - description: Enabled pull-up bits.
+          - description: Disabled pull-up bits.
+          - description: Pull-up mask.
+        additionalItems: false
+
+      pinctrl-packed,bias-pulldown:
+        description: Optional bias pull-down configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 4
+        items:
+          - description: Input value.
+          - description: Enabled pull-down bits.
+          - description: Disabled pull-down bits.
+          - description: Pull-down mask.
+        additionalItems: false
+
+      pinctrl-packed,drive-strength:
+        description: Optional drive strength configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 2
+        items:
+          - description: Drive strength value.
+          - description: Drive strength mask.
+        additionalItems: false
+
+      pinctrl-packed,input-schmitt:
+        description: Optional input Schmitt trigger configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 2
+        items:
+          - description: Schmitt trigger value.
+          - description: Schmitt trigger mask.
+        additionalItems: false
+
+      pinctrl-packed,input-schmitt-enable:
+        description: Optional input Schmitt enable configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 4
+        items:
+          - description: Input value.
+          - description: Enable bits.
+          - description: Disable bits.
+          - description: Schmitt mask.
+        additionalItems: false
+
+      pinctrl-packed,low-power-mode:
+        description: Optional low power mode configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 2
+        items:
+          - description: Low power value.
+          - description: Low power mask.
+        additionalItems: false
+
+      pinctrl-packed,slew-rate:
+        description: Optional slew rate configuration.
+        $ref: /schemas/types.yaml#/definitions/uint32-array
+        maxItems: 2
+        items:
+          - description: Slew rate value.
+          - description: Slew rate mask.
+        additionalItems: false
+
+required:
+  - compatible
+  - reg
+  - "#pinctrl-cells"
+  - pinctrl-packed,function-mask
+
+additionalProperties: false
+
+allOf:
+  - $ref: pinctrl.yaml#
+
+examples:
+  - |
+    syscon@0 {
+        compatible = "syscon", "simple-mfd";
+        reg = <0x0 0x1000>;
+        ranges;
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        pinctrl@400 {
+            compatible = "pinctrl-packed";
+            reg = <0x400 0x80>;
+            #pinctrl-cells = <1>;
+            pinctrl-packed,function-mask = <0xf>;
+
+            uart0-pins {
+                /* <pin_index function_select> pairs */
+                pinctrl-packed,pins = <0 2>, <1 2>;
+            };
+        };
+    };

-- 
2.34.1