[PATCH v3 4/4] dt-bindings: iio: adc: ad7949: add per channel reference

[Liam Beguin <liambeguin@gmail.com>]

From: Liam Beguin <lvb@xiphos.com>

Add bindings documentation describing per channel reference voltage
selection.
This adds the adi,internal-ref-mv property, and child nodes for each
channel. This is required to properly configure the ADC sample request
based on which reference source should be used for the calculation.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 .../bindings/iio/adc/adi,ad7949.yaml          | 71 +++++++++++++++++--
 1 file changed, 67 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
index 9b56bd4d5510..18abba3b0b4d 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7949.yaml
@@ -26,19 +26,65 @@ properties:
   reg:
     maxItems: 1
 
+  vrefin-supply:
+    description:
+      Buffered ADC reference voltage supply.
+
   vref-supply:
     description:
-      ADC reference voltage supply
+      Unbuffered ADC reference voltage supply.
 
   spi-max-frequency: true
 
-  "#io-channel-cells":
+  '#io-channel-cells':
     const: 1
 
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+
 required:
   - compatible
   - reg
-  - vref-supply
+
+patternProperties:
+  '^channel@([0-7])$':
+    type: object
+    description: |
+      Represents the external channels which are connected to the ADC.
+
+    properties:
+      reg:
+        description: |
+          The channel number.
+          Up to 4 channels, numbered from 0 to 3 for adi,ad7682.
+          Up to 8 channels, numbered from 0 to 7 for adi,ad7689 and adi,ad7949.
+        items:
+          minimum: 0
+          maximum: 7
+
+      adi,internal-ref-mv:
+        description: |
+          Internal reference voltage selection in millivolts.
+
+          If no internal reference is specified, the channel will default to the
+          external reference defined by vrefin-supply (or vref-supply).
+          vrefin-supply will take precedence over vref-supply if both are defined.
+
+          If no supplies are defined, the reference selection will default to
+          4096mV internal reference.
+
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [2500, 4096]
+        default: 4096
+
+    required:
+      - reg
+
+    additionalProperties: false
 
 additionalProperties: false
 
@@ -49,9 +95,26 @@ examples:
         #size-cells = <0>;
 
         adc@0 {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
             compatible = "adi,ad7949";
             reg = <0>;
-            vref-supply = <&vdd_supply>;
+            vrefin-supply = <&vdd_supply>;
+
+            channel@0 {
+                adi,internal-ref-mv = <4096>;
+                reg = <0>;
+            };
+
+            channel@1 {
+                adi,internal-ref-mv = <2500>;
+                reg = <1>;
+            };
+
+            channel@2 {
+                reg = <2>;
+            };
         };
     };
 ...
-- 
2.30.1.489.g328c10930387