[PATCH 1/7] dt-bindings: iio: adc: add generic channel binding

[Olivier Moysan]

Add ADC generic channel binding. This binding should
be used as an alternate to legacy channel properties
whenever possible.
ADC generic channel binding allows to identify supported
internal channels through the following reserved label names:
"vddcore", "vrefint" and "vbat".
This binding also allows to set a different sampling time
for each channel.

Signed-off-by: Olivier Moysan <olivier.moysan at foss.st.com>
---
Note: The schema here is too permissive as either legacy or generic
channels properties are required. These properties are mutually
exclusive, however all attempts to describe this constraint are
failing. In particular the following schemas and their variants have
shown unsucessful.

oneOf:
  - anyOf:
	- required:
		- st,adc-channels
	- required:
		- st,adc-diff-channels
  - anyOf:
	- required:
		- $nodename

- if:
  patternProperties:
    "^channel@([0-9]|1[0-9])$":
      type: object
then:
  properties:
    st,adc-channels: false
    st,adc-diff-channels: false
else:
  - anyOf:
      - required:
          - st,adc-channels
      - required:
          - st,adc-diff-channels
---
 .../bindings/iio/adc/st,stm32-adc.yaml        | 100 ++++++++++++++++--
 1 file changed, 93 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.yaml
index a58334c3bb76..a1f6cbe144ba 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.yaml
@@ -222,6 +222,12 @@ patternProperties:
       '#io-channel-cells':
         const: 1
 
+      '#address-cells':
+        const: 1
+
+      '#size-cells':
+        const: 0
+
       interrupts:
         description: |
           IRQ Line for the ADC instance. Valid values are:
@@ -265,7 +271,9 @@ patternProperties:
           <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered from 0 to 19.
 
           Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is
-          required. Both properties can be used together. Some channels can be
+          required if no adc generic channel is defined. These legacy channel
+          properties are exclusive with adc generic channel bindings.
+          Both properties can be used together. Some channels can be
           used as single-ended and some other ones as differential (mixed). But
           channels can't be configured both as single-ended and differential.
         $ref: /schemas/types.yaml#/definitions/uint32-matrix
@@ -290,6 +298,44 @@ patternProperties:
           each channel.
         $ref: /schemas/types.yaml#/definitions/uint32-array
 
+    patternProperties:
+      "^channel@([0-9]|1[0-9])$":
+        type: object
+        $ref: "adc.yaml"
+        description: |
+          Represents the external channels which are connected to the ADC.
+
+        properties:
+          reg:
+            items:
+              minimum: 0
+              maximum: 19
+
+          label:
+            description: |
+              Unique name to identify which channel this is.
+              Reserved label names "vddcore", "vrefint" and "vbat"
+              are used to identify internal channels with matching names.
+
+          diff-channels:
+            $ref: /schemas/types.yaml#/definitions/uint32-array
+            items:
+              minimum: 0
+              maximum: 19
+
+          st,min-sample-time-nsecs:
+            $ref: /schemas/types.yaml#/definitions/uint32
+            description: |
+              Minimum sampling time in nanoseconds. Depending on hardware (board)
+              e.g. high/low analog input source impedance, fine tune of ADC
+              sampling time may be recommended.
+
+        required:
+          - reg
+
+    dependencies:
+      $nodename: [ '#address-cells', '#size-cells' ]
+
     allOf:
       - if:
           properties:
@@ -369,12 +415,6 @@ patternProperties:
 
     additionalProperties: false
 
-    anyOf:
-      - required:
-          - st,adc-channels
-      - required:
-          - st,adc-diff-channels
-
     required:
       - compatible
       - reg
@@ -451,4 +491,50 @@ examples:
         // other adc child node follow...
       };
 
+  - |
+    // Example 3: with stm32mp157c to setup ADC2 with:
+    // - internal channels 13, 14, 15.
+      #include <dt-bindings/interrupt-controller/arm-gic.h>
+      #include <dt-bindings/clock/stm32mp1-clks.h>
+      adc122: adc at 48003000 {
+        compatible = "st,stm32mp1-adc-core";
+        reg = <0x48003000 0x400>;
+        interrupts = <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH>,
+                     <GIC_SPI 90 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&rcc ADC12>, <&rcc ADC12_K>;
+        clock-names = "bus", "adc";
+        booster-supply = <&booster>;
+        vdd-supply = <&vdd>;
+        vdda-supply = <&vdda>;
+        vref-supply = <&vref>;
+        st,syscfg = <&syscfg>;
+        interrupt-controller;
+        #interrupt-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        adc at 100 {
+          compatible = "st,stm32mp1-adc";
+          #io-channel-cells = <1>;
+          reg = <0x100>;
+          interrupts = <1>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+          channel at 13 {
+            reg = <13>;
+            label = "vrefint";
+            st,min-sample-time-nsecs = <9000>;
+          };
+          channel at 14 {
+            reg = <14>;
+            label = "vddcore";
+            st,min-sample-time-nsecs = <9000>;
+          };
+          channel at 15 {
+            reg = <15>;
+            label = "vbat";
+            st,min-sample-time-nsecs = <9000>;
+          };
+        };
+      };
+
 ...
-- 
2.17.1