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Message-ID: <f2ac13fc-8f47-465e-8cef-e2e34bf41818@baylibre.com> Date: Wed, 19 Nov 2025 08:45:42 -0600 From: David Lechner <dlechner@...libre.com> To: Rob Herring <robh@...nel.org> Cc: Mark Brown <broonie@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Marcelo Schmitt <marcelo.schmitt@...log.com>, Michael Hennerich <michael.hennerich@...log.com>, Nuno Sá <nuno.sa@...log.com>, Jonathan Cameron <jic23@...nel.org>, Andy Shevchenko <andy@...nel.org>, Sean Anderson <sean.anderson@...ux.dev>, linux-spi@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org Subject: Re: [PATCH v2 5/6] dt-bindings: iio: adc: adi,ad7380: add spi-buses property On 11/19/25 7:18 AM, Rob Herring wrote: > On Tue, Nov 18, 2025 at 11:46 AM David Lechner <dlechner@...libre.com> wrote: >> >> On 11/18/25 9:59 AM, Rob Herring wrote: >>> On Fri, Nov 07, 2025 at 02:52:51PM -0600, David Lechner wrote: >>>> Add spi-buses property to describe how many SDO lines are wired up on >>>> the ADC. These chips are simultaneous sampling ADCs and have one SDO >>>> line per channel, either 2 or 4 total depending on the part number. >>>> >>>> Signed-off-by: David Lechner <dlechner@...libre.com> >>>> --- >>>> .../devicetree/bindings/iio/adc/adi,ad7380.yaml | 22 ++++++++++++++++++++++ >>>> 1 file changed, 22 insertions(+) >>>> >>>> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml >>>> index b91bfb16ed6bc6c605880f81050250d1ed9c307a..9ef46cdb047d45d088e0fbc345f58c5b09083385 100644 >>>> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml >>>> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml >>>> @@ -62,6 +62,10 @@ properties: >>>> spi-cpol: true >>>> spi-cpha: true >>>> >>>> + spi-data-buses: >>>> + minItems: 1 >>>> + maxItems: 4 >>>> + >>> >>> As the property is not required, what's the default? >> >> spi-perepheral-props.yaml defines: >> >> default: [0] >> >> Do I need to repeat that here? > > No. So that means you only use one channel and the others are not connected? Correct. > >> >>> >>>> vcc-supply: >>>> description: A 3V to 3.6V supply that powers the chip. >>>> >>>> @@ -245,6 +249,22 @@ allOf: >>>> patternProperties: >>>> "^channel@[0-3]$": false >>>> >>>> + # 2-channel chip can only have up to 2 buses >>>> + - if: >>>> + properties: >>>> + compatible: >>>> + enum: >>>> + - adi,ad7380 >>>> + - adi,ad7381 >>>> + - adi,ad7386 >>>> + - adi,ad7387 >>>> + - adi,ad7388 >>>> + - adi,ad7389 >>>> + then: >>>> + properties: >>>> + spi-data-buses: >>>> + maxItems: 2 >>>> + >>>> examples: >>>> - | >>>> #include <dt-bindings/interrupt-controller/irq.h> >>>> @@ -260,6 +280,7 @@ examples: >>>> spi-cpol; >>>> spi-cpha; >>>> spi-max-frequency = <80000000>; >>>> + spi-data-buses = <0>, <1>; >>>> >>>> interrupts = <27 IRQ_TYPE_EDGE_FALLING>; >>>> interrupt-parent = <&gpio0>; >>>> @@ -284,6 +305,7 @@ examples: >>>> spi-cpol; >>>> spi-cpha; >>>> spi-max-frequency = <80000000>; >>>> + spi-data-buses = <0>, <1>, <2>, <3>; >>> >>> An example that doesn't look like a 1 to 1 mapping would be better. >>> Otherwise, it still looks to me like you could just define the bus >>> width. >> >> I'm not sure we could do that on this chip since it doesn't have >> the possibility of more than one line per channel. > > That's a property of the SPI controller though, right? > > If the above controller had 4 lines per channel/serializer, then you could have: > > spi-data-buses = <0>, <4>, <8>, <12>; Ah, I get what you mean now. The intention here though was that the index numbers correspond to the data lane (channel/serializer), not to individual lines. So the example you gave would mean that the chip has at least 13 data lanes (rather than what I think your intention was of saying it has at least 16 data wires). I did it that way because all of the hardware I looked at didn't allow assigning arbitrary data lines to arbitrary lanes/channels so it keeps things simpler and easier to match to the actual hardware docs. I intend to change the property name to data-lanes so I will use that below instead of spi-data-buses. For this ADC, I would still write: data-lanes: <0>, <1>, <2>, <3>; to mean: +--------------+ +----------+ | SPI | | AD7380-4 | | Controller | | ADC | | | | | | SDIA0 |<---| SDOA | | SDIA1 |x | | | SDIA2 |x | | | SDIA3 |x | | | | | | | SDIB0 |<---| SDOB | | SDIB1 |x | | | SDIB2 |x | | | SDIB3 |x | | | | | | | SDIC0 |<---| SDOC | | SDIC1 |x | | | SDIC2 |x | | | SDIC3 |x | | | | | | | SDID0 |<---| SDOD | | SDID1 |x | | | SDID2 |x | | | SDID3 |x | | | | | | +--------------+ +---------+ I.e. lanes <0>=A, <1>=B, <2>=C, <3>=D and there is an implied default spi-rx-bus-width = <1>; For another chip we are working on, we could have: spi-rx-bus-width = <4>; data-lanes: <0>, <1>; Meaning: +--------------+ +----------+ | SPI | | AD4630 | | Controller | | ADC | | | | | | SDIA0 |<---| SDOA0 | | SDIA1 |<---| SDOA1 | | SDIA2 |<---| SDOA2 | | SDIA3 |<---| SDOA3 | | | | | | SDIB0 |<---| SDOB0 | | SDIB1 |<---| SDOB1 | | SDIB2 |<---| SDOB2 | | SDIB3 |<---| SDOB3 | | | | | | SDIC0 |x | | | SDIC1 |x | | | SDIC2 |x | | | SDIC3 |x | | | | | | | SDID0 |x | | | SDID1 |x | | | SDID2 |x | | | SDID3 |x | | | | | | +--------------+ +---------+ > > Rob
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