On echo and host clock modes, AD4030 and similar devices can do two data
bit transitions per clock cycle per active lane. Document how to specify
dual data rate (DDR) feature for AD4030 series devices in device tree.

Co-developed-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
 .../bindings/iio/adc/adi,ad4030.yaml          | 27 +++++++++++++++----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
index 1e4e025b835f..9adb60629631 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
@@ -90,6 +90,13 @@ properties:
       host - Host. The Host clock mode uses an internal oscillator to clock out
              the data bits. In this mode, the spi controller is not driving SCLK.
 
+  adi,dual-data-rate:
+    description:
+      Enable dual data rate (DDR) in which two bits (per active lane) are
+      transmitted in one clock cycle. This can reduce the serial clock to
+      10 MHz while operating at a sample rate of 2 MSPS.
+    type: boolean
+
 required:
   - compatible
   - reg
@@ -98,11 +105,21 @@ required:
   - vio-supply
   - cnv-gpios
 
-oneOf:
-  - required:
-      - ref-supply
-  - required:
-      - refin-supply
+allOf:
+  - oneOf:
+      - required:
+          - ref-supply
+      - required:
+          - refin-supply
+  # DDR is available only for echo clock mode and host clock mode.
+  - if:
+      properties:
+        adi,clock-mode:
+          contains:
+            const: spi
+    then:
+      properties:
+        adi,dual-data-rate: false
 
 unevaluatedProperties: false
 
-- 
2.39.2

On 8/29/25 7:44 PM, Marcelo Schmitt wrote:
> On echo and host clock modes, AD4030 and similar devices can do two data
> bit transitions per clock cycle per active lane. Document how to specify
> dual data rate (DDR) feature for AD4030 series devices in device tree.
> 
I don't think this needs to be in the devicetree. Dual data rate doesn't
depend on wiring, it only depends on if the SPI controller supports it
or not. The core SPI code in Linux already has dtr_caps for SPI controllers
to indicate that they have DDR support. So an ADC driver can just check
this flag to see if the controller supports it. No devicetree flags required.