dt-bindings: iio: stm32-adc: add generic channel binding

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@foss.st.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211014131228.4692-2-olivier.moysan@foss.st.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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:
@@ -256,6 +262,7 @@ patternProperties:
             - 20 channels, numbered from 0 to 19 (for in0..in19) on stm32h7 and
               stm32mp1.
         $ref: /schemas/types.yaml#/definitions/uint32-array
+        deprecated: true
 
       st,adc-diff-channels:
         description: |
@@ -265,7 +272,9 @@ 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
@@ -279,6 +288,7 @@ patternProperties:
                 "vinn" indicates negative input number
               minimum: 0
               maximum: 19
+        deprecated: true
 
       st,min-sample-time-nsecs:
         description:
@@ -289,6 +299,42 @@ patternProperties:
           list, to set sample time resp. for all channels, or independently for
           each channel.
         $ref: /schemas/types.yaml#/definitions/uint32-array
+        deprecated: true
+
+    patternProperties:
+      "^channel@([0-9]|1[0-9])$":
+        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-ns:
+            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
+
+        additionalProperties: false
 
     allOf:
       - if:
@@ -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@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@100 {
+          compatible = "st,stm32mp1-adc";
+          #io-channel-cells = <1>;
+          reg = <0x100>;
+          interrupts = <1>;
+          #address-cells = <1>;
+          #size-cells = <0>;
+          channel@13 {
+            reg = <13>;
+            label = "vrefint";
+            st,min-sample-time-ns = <9000>;
+          };
+          channel@14 {
+            reg = <14>;
+            label = "vddcore";
+            st,min-sample-time-ns = <9000>;
+          };
+          channel@15 {
+            reg = <15>;
+            label = "vbat";
+            st,min-sample-time-ns = <9000>;
+          };
+        };
+      };
+
 ...