[PATCH v5 02/14] dt-bindings: iio: adc: ad7768-1: add trigger-sources property

Jonathan Santos
2025-04-11T15:56:53Z

In addition to GPIO synchronization, The AD7768-1 also supports
synchronization over SPI, which use is recommended when the GPIO
cannot provide a pulse synchronous with the base MCLK signal. It
consists of looping back the SYNC_OUT to the SYNC_IN pin and send
a command via SPI to trigger the synchronization.

Introduce the 'trigger-sources' property to support SPI-based
synchronization, along with additional optional entries for the SPI
offload trigger and the START signal via GPIO3.

While at it, add description to the interrupts property.

Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
v5 Changes:
* Include START pin and DRDY in the trigger-sources description.
* Fixed "#trigger-source-cells" value and description.
* sync-in-gpios is represented in the trigger-sources property.

v4 Changes:
* none

v3 Changes:
* Fixed dt-bindings errors.
* Trigger-source is set as an alternative to sync-in-gpios, so we
don't break the previous ABI.
* increased maxItems from trigger-sources to 2.

v2 Changes:
* Patch added as replacement for adi,sync-in-spi patch.
* addressed the request for a description to interrupts property.
---
.../bindings/iio/adc/adi,ad7768-1.yaml | 38 +++++++++++++++++--
1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
index 3ce59d4d065f..4c58dbe8f749 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
@@ -26,7 +26,30 @@ properties:
clock-names:
const: mclk

+ trigger-sources:
+ $ref: /schemas/types.yaml#/definitions/phandle-array
+ minItems: 1
+ maxItems: 3
+ description: |
+ A list of phandles referencing trigger source devices or GPIOs.
+ Supports up to three entries, each representing a different type of
+ trigger:
+
+ - First entry specifies the device responsible for driving the
+ synchronization (SYNC_IN) pin, as an alternative to adi,sync-in-gpios.
+ This can be a `gpio-trigger` or another `ad7768-1` device. If the
+ device's own SYNC_OUT pin is internally connected to its SYNC_IN pin,
+ reference the device itself or omit this property.
+ - Second entry optionally defines a GPIO3 pin used as a START signal trigger.
+ - Third entry specifies a GPIO line to act as a trigger for SPI offload.
+
+ Use the accompanying trigger source cell to identify the type of each entry.
+
interrupts:
+ description:
+ Specifies the interrupt line associated with the ADC. This refers
+ to the DRDY (Data Ready) pin, which signals when conversion results are
+ available.
maxItems: 1

'#address-cells':
@@ -57,6 +80,15 @@ properties:
"#io-channel-cells":
const: 1

+ "#trigger-source-cells":
+ description: |
+ Indicates the trigger source type for each entry:
+ 0 = Synchronization GPIO-based trigger
+ 1 = Synchronization device trigger (e.g., another ad7768-1)
+ 2 = GPIO3 pin acting as START signal
+ 3 = DRDY pin acting as SPI offload trigger
+ const: 1
+
required:
- compatible
- reg
@@ -65,7 +97,6 @@ required:
- vref-supply
- spi-cpol
- spi-cpha
- - adi,sync-in-gpios

patternProperties:
"^channel@([0-9]|1[0-5])$":
@@ -99,7 +130,7 @@ examples:
#address-cells = <1>;
#size-cells = <0>;

- adc@0 {
+ adc0: adc@0 {
compatible = "adi,ad7768-1";
reg = <0>;
spi-max-frequency = <2000000>;
@@ -108,7 +139,8 @@ examples:
vref-supply = <&adc_vref>;
interrupts = <25 IRQ_TYPE_EDGE_RISING>;
interrupt-parent = <&gpio>;
- adi,sync-in-gpios = <&gpio 22 GPIO_ACTIVE_LOW>;
+ trigger-sources = <&adc0 1>;
+ #trigger-source-cells = <1>;
reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
clocks = <&ad7768_mclk>;
clock-names = "mclk";
--
2.34.1