Re: [PATCH v2 1/2] dt-bindings: iio: dac: Add adi,ad3552r.yaml

On Mon, 11 Oct 2021 08:37:44 +0000
"Chindris, Mihail" [off-list ref] wrote:

quoted

-----Original Message-----
From: Jonathan Cameron <jic23@kernel.org>
Sent: Sunday, 10 October 2021 17:49
To: Chindris, Mihail <redacted>
Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
lars@metafoo.de; Hennerich, Michael [off-list ref];
Sa, Nuno [off-list ref]; Bogdan, Dragos
[off-list ref]; alexandru.ardelean@analog.com; Mark
Brown [off-list ref]
Subject: Re: [PATCH v2 1/2] dt-bindings: iio: dac: Add adi,ad3552r.yaml

On Fri, 8 Oct 2021 12:39:08 +0000
Mihail Chindris [off-list ref] wrote:
  

quoted

Add documentation for ad3552r

Signed-off-by: Mihail Chindris <redacted>  

Hi Mihael,

A few comments inline.

Thanks,

Jonathan

Just realized this is missing cc for Rob + dt list which is a must for
any new binding doc.  Query for Rob inline.

Thanks,

Jonathan

quoted

quoted

---
 .../bindings/iio/dac/adi,ad3552r.yaml         | 199 ++++++++++++++++++
 1 file changed, 199 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml

diff --git
a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
new file mode 100644
index 000000000000..1086e935d330

--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml

@@ -0,0 +1,199 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) # Copyright 2020
+Analog Devices Inc.
+%YAML 1.2
+---
+$id:
+https://urldefense.com/v3/__http://devicetree.org/schemas/iio/dac/adi
 

+,ad3552r.yaml*__;Iw!!A3Ni8CS0y2Y!pqvd1NyV8G8KXIcfAtV1erPpylxLUGXD
1Tx5  

quoted

+UoK2MMNNgQpv5RSyFb6NQDSL0sEuJOI$
+$schema:
+https://urldefense.com/v3/__http://devicetree.org/meta-  

schemas/core.y  

quoted

+aml*__;Iw!!A3Ni8CS0y2Y!pqvd1NyV8G8KXIcfAtV1erPpylxLUGXD1Tx5UoK2
MMNNgQ  

quoted

+pv5RSyFb6NQDSL3G5680U$
+
+title: Analog Devices AD2552R DAC device driver
+
+maintainers:
+  - Mihail Chindris [off-list ref]
+
+description: |
+  Bindings for the Analog Devices AD3552R  DAC device. Datasheet can
+be  

Extra space before DAC, and doesn't mention the other supported part.
One option to avoid a never ending list is "and similar."
  

quoted

+  found here:
+
+ https://www.analog.com/media/en/technical-documentation/data-  

sheets/  

quoted

+ ad3552r.pdf  

Good to have datasheet for the other part as well as I don't think this is a
shared datasheet?
  

quoted

+
+properties:
+  compatible:
+    enum:
+      - adi,ad3552r
+      - adi,ad3542r  

Alphabetical order preferred.
  

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+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 30000000
+
+  reset-gpios:
+    maxItems: 1
+
+  ldac-gpios:
+    description: |
+      If a LDAC gpio is specified it will generate a LDAC pulse each time the
+      trigger handler sends data to the chip.  

Trigger handler is a linux concept. You need to write this more generically.
Something like.

"LDAC pin is used as a hardware trigger to update a set of DACs."

  

quoted

+    maxItems: 1
+
+  vref-supply:
+    description:
+      The regulator to use as an external reference. If it does not exists the
+      internal reference will be used. External reference must be
+ 2.5V
+
+  adi,vref-out-en:
+    description: Vref I/O driven by internal vref to 2.5V. If not set, Vref pin
+      will be floating.
+    type: boolean
+
+  adi,sdo-drive-strength:
+    description: |
+      Configure SDIO0 and SDIO1 strength levels:
+        - 0: low SDO drive strength.
+        - 1: medium low SDO drive strength.
+        - 2: medium high SDO drive strength.
+        - 3: high SDO drive strength
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [0, 1, 2, 3]
+
+patternProperties:
+  "^channel@([0-1])$":
+    type: object
+    description: Configurations of the DAC Channels
+    properties:
+      reg:
+          description: Channel number
+          enum: [0, 1]
+
+      custom-output-range-config:  

Not a generic property so I think this needs an adi prefix.  

I tried with adi prefix but I get weird errors while running dt_binding_check for properties with adi prefix and with type:object
Do you have any suggestion for this issues?

@Rob

quoted

quoted

+        type: object
+        description: Configuration of custom range when
+          adi,output-range-microvolt is not present.
+          The formulas for calculation the output voltages are
+            Vout_fs = 2.5 + [(GainN + Offset/1024) * 2.5 * Rfbx * 1.03]
+            Vout_zs = 2.5 - [(GainP + Offset/1024) * 2.5 * Rfbx * 1.03]
+        properties:
+          adi,gain-offset:
+            description: Gain offset used in the above formula
+            $ref: /schemas/types.yaml#/definitions/int32
+            maximum: 511
+            minimum: -511
+          adi,gain-scaling-p:
+            description: |
+              Scaling p:
+               0: 1.0
+               1: 0.5
+               2: 0.25
+               3: 0.125  

Given this is just a mapping to a simple set of values, could we just have the
values or express it as 1/(2^GainP) in the equation above and call it
adi,gain-scalling-inv-log2 or something like that?

If we can avoid a mapping table that is always a nice to have

  

quoted

+            $ref: /schemas/types.yaml#/definitions/uint32
+            enum: [0, 1, 2, 3]
+          adi,gain-scaling-n:
+            description: |
+              Scaling p:
+               0: 1.0
+               1: 0.5
+               2: 0.25
+               3: 0.125
+            $ref: /schemas/types.yaml#/definitions/uint32
+            enum: [0, 1, 2, 3]
+          adi,rfb-ohms:
+            description: Feedback Resistor
+        required:
+          - adi,gain-offset
+          - adi,gain-sacling-p
+          - adi,gain-sacling-n
+          - adi,rfb-ohms
+    required:
+      - reg
+
+    oneOf:
+      # If adi,output-range is missing, custom-output-range-config
+ must be used  

adi,output-range-microvolt is missing...
  

quoted

+      - required:
+        - adi,output-range-microvolt
+      - required:
+        - custom-output-range-config
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,ad3542r
+    then:
+      patternProperties:
+        "^channel@([0-1])$":
+          type: object
+          properties:
+            adi,output-range-microvolt:
+              description: |
+                Voltage output range of the channel as <minimum, maximum>
+                Required connections:
+                  Rfb1x for: 0 to 2.5 V; 0 to 3V; 0 to 5 V;
+                  Rfb2x for: 0 to 10 V; 2.5 to 7.5V; -5 to 5 V;
+              oneOf:
+                - items:
+                    - const: 0
+                    - enum: [2500000, 3000000, 5000000, 10000000]
+                - items:
+                    - const: -2500000
+                    - const: 7500000
+                - items:
+                    - const: -5000000
+                    - const: 5000000
+          required:
+            - adi,output-range-microvolt
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,ad3552r
+    then:
+      patternProperties:
+        "^channel@([0-1])$":
+          type: object
+          properties:
+            adi,output-range-microvolt: |
+                Voltage output range of the channel as <minimum, maximum>
+                Required connections:
+                  Rfb1x for: 0 to 2.5 V; 0 to 5 V;
+                  Rfb2x for: 0 to 10 V; -5 to 5 V;
+                  Rfb4x for: -10 to 10V
+              oneOf:
+                - items:
+                    - const: 0
+                    - enum: [2500000, 5000000, 10000000]
+                - items:
+                    - const: -5000000
+                    - const: 5000000
+                - items:
+                    - const: -10000000
+                    - const: 10000000
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+
+additionalProperties: false
+
+examples:
+  - |
+    ad3552r {
+            compatible = "adi,ad3552r";
+            reg = <0>;
+            spi-max-frequency = <20000000>;
+            channel@0 {
+                    reg = <0>;
+                    adi,output-range-microvolt = <0 10000000>;
+            };
+            channel@1 {
+                    reg = <1>;
+                    custom-output-range-config {
+                            adi,gain-offset = <5>;
+                            adi,gain-scaling-p = <1>;
+                            adi,gain-scaling-n = <2>;
+                            adi,rfb-ohms = <1>;
+                    };
+          };
+      };
+...