On 02/13, Conor Dooley wrote:
> On Wed, Feb 12, 2025 at 03:16:16PM -0300, Jonathan Santos wrote:
> > 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.
> >
> > Add a new trigger-sources property to enable synchronization over SPI
> > and future multiple devices support. This property references the
> > main device (or trigger provider) responsible for generating the
> > SYNC_OUT pulse to drive the SYNC_IN of device.
> >
> > While at it, add description to the interrupts property.
> >
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
> > ---
> > 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 | 28 +++++++++++++++++--
> > 1 file changed, 25 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..4bcc9e20fab9 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > @@ -26,7 +26,19 @@ properties:
> > clock-names:
> > const: mclk
> >
> > + trigger-sources:
> > + description:
> > + Specifies the device responsible for driving the synchronization pin,
> > + as an alternative to adi,sync-in-gpios. If the own device node is
> > + referenced, The synchronization over SPI is enabled and the SYNC_OUT
> > + output will drive the SYNC_IN pin.
>
> Maybe a silly question, but why is self-reference needed here?
> sync-in-gpios is a required property at present, so why can't you
> operate under the assumption that neither the trigger-sources when
> neither are present? Is it because only one of the sources could be
> external and one internal, or there could be either one or two internal
> sources? Self-referencing properties always feel like a bit of a
> mistake.
>
We have one internal synchronization source and two external ones.
The internal is when /SYNC_OUT drives /SYNC_IN (in this case with self
referencing). The external sources include using a GPIO to drive the
/SYNC_IN (sync-in-gpio case) or using an external /SYNC_OUT, the last one
is described in the datasheet for multi-devices setup.
The trigger-sources property is inteded to indicate wheter the /SYNC_OUT
signal originates from within the device or from another source. currently
we are only handling the internal case. We are not sure yet how to handle
the external sources.
> > + maxItems: 2
> > +
> > 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 +69,9 @@ properties:
> > "#io-channel-cells":
> > const: 1
> >
> > + "#trigger-source-cells":
> > + const: 0
> > +
> > required:
> > - compatible
> > - reg
> > @@ -65,7 +80,6 @@ required:
> > - vref-supply
> > - spi-cpol
> > - spi-cpha
> > - - adi,sync-in-gpios
> >
> > patternProperties:
> > "^channel@([0-9]|1[0-5])$":
> > @@ -89,6 +103,13 @@ patternProperties:
> > allOf:
> > - $ref: /schemas/spi/spi-peripheral-props.yaml#
> >
> > + - oneOf:
> > + - required:
> > + - trigger-sources
> > + - "#trigger-source-cells"
> > + - required:
> > + - adi,sync-in-gpios
> > +
> > unevaluatedProperties: false
> >
> > examples:
> > @@ -99,7 +120,7 @@ examples:
> > #address-cells = <1>;
> > #size-cells = <0>;
> >
> > - adc@0 {
> > + adc0: adc@0 {
> > compatible = "adi,ad7768-1";
> > reg = <0>;
> > spi-max-frequency = <2000000>;
> > @@ -108,7 +129,8 @@ 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 0>;
> > + #trigger-source-cells = <0>;
> > reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
> > clocks = <&ad7768_mclk>;
> > clock-names = "mclk";
> > --
> > 2.34.1
> >
