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Mon, 22 Jun 2026 03:28:36 -0700 (PDT) Date: Mon, 22 Jun 2026 11:29:38 +0100 From: Nuno =?utf-8?B?U8Oh?= To: Rodrigo Alencar <455.rodrigo.alencar@gmail.com> Cc: Jonathan Cameron , Conor Dooley , Janani Sunil , Janani Sunil , Lars-Peter Clausen , Michael Hennerich , David Lechner , Nuno =?utf-8?B?U8Oh?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Philipp Zabel , Jonathan Corbet , Shuah Khan , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Mark Brown Subject: Re: [PATCH v3 1/2] dt-bindings: iio: dac: Add AD5529R Message-ID: References: <603473ac-30e6-45e5-8a3b-c9902715cc9e@gmail.com> <20260614204455.408c4d40@jic23-huawei> <076d7d2d-81a0-49c2-af94-bd65ead66c09@gmail.com> <20260619-obstinate-polo-a230bef97fda@spud> <20260619-bunch-diocese-dd7805cc17ff@spud> <20260619-concierge-doozy-9c161533c369@spud> <20260621153330.79b6600c@jic23-huawei> <5u4dnsgxwcwie45f24cacyzf3dko4srhyyyhcpom6tsvhqtmpc@y7d7gmex6n7k> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5u4dnsgxwcwie45f24cacyzf3dko4srhyyyhcpom6tsvhqtmpc@y7d7gmex6n7k> On Mon, Jun 22, 2026 at 10:24:05AM +0100, Rodrigo Alencar wrote: > On 21/06/26 15:33, Jonathan Cameron wrote: > > On Fri, 19 Jun 2026 16:54:11 +0100 > > Nuno Sá wrote: > > > > > On Fri, Jun 19, 2026 at 03:12:07PM +0100, Conor Dooley wrote: > > > > On Fri, Jun 19, 2026 at 02:01:08PM +0100, Nuno Sá wrote: > > > > > On Fri, Jun 19, 2026 at 12:40:54PM +0100, Conor Dooley wrote: > > > > > > On Fri, Jun 19, 2026 at 12:36:55PM +0100, Conor Dooley wrote: > > > > > > > On Fri, Jun 19, 2026 at 12:33:11PM +0200, Janani Sunil wrote: > > > > > > > > > > > > > > > > On 6/14/26 21:44, Jonathan Cameron wrote: > > > > > > > > > On Tue, 9 Jun 2026 16:47:23 +0200 > > > > > > > > > Janani Sunil wrote: > > > > > > > > > > > > > > > > > > > On 5/26/26 15:11, Rodrigo Alencar wrote: > > > > > > > > > > > On 26/05/19 05:42PM, Janani Sunil wrote: > > > > > > > > > > > > Devicetree bindings for AD5529R 16 channel 12/16 bit high voltage, > > > > > > > > > > > > buffered voltage output digital-to-analog converter (DAC) with an > > > > > > > > > > > > integrated precision reference. > > > > > > > > > > > ... > > > > > > > > > > > Probably others may comment on that, but... > > > > > > > > > > > > > > > > > > > > > > This parent node may support device addressing for multi-device support through > > > > > > > > > > > those ID pins. I suppose that each device may have its own power supplies or > > > > > > > > > > > other resources like the toggle pins or reset and enable. > > > > > > > > > > > > > > > > > > > > > > That way I suppose that an example would look like... > > > > > > > > > > > > + > > > > > > > > > > > > +patternProperties: > > > > > > > > > > > > + "^channel@([0-9]|1[0-5])$": > > > > > > > > > > > > + type: object > > > > > > > > > > > > + description: Child nodes for individual channel configuration > > > > > > > > > > > > + > > > > > > > > > > > > + properties: > > > > > > > > > > > > + reg: > > > > > > > > > > > > + description: Channel number. > > > > > > > > > > > > + minimum: 0 > > > > > > > > > > > > + maximum: 15 > > > > > > > > > > > > + > > > > > > > > > > > > + adi,output-range-microvolt: > > > > > > > > > > > > + description: | > > > > > > > > > > > > + Output voltage range for this channel as [min, max] in microvolts. > > > > > > > > > > > > + If not specified, defaults to 0V to 5V range. > > > > > > > > > > > > + oneOf: > > > > > > > > > > > > + - items: > > > > > > > > > > > > + - const: 0 > > > > > > > > > > > > + - enum: [5000000, 10000000, 20000000, 40000000] > > > > > > > > > > > > + - items: > > > > > > > > > > > > + - const: -5000000 > > > > > > > > > > > > + - const: 5000000 > > > > > > > > > > > > + - items: > > > > > > > > > > > > + - const: -10000000 > > > > > > > > > > > > + - const: 10000000 > > > > > > > > > > > > + - items: > > > > > > > > > > > > + - const: -15000000 > > > > > > > > > > > > + - const: 15000000 > > > > > > > > > > > > + - items: > > > > > > > > > > > > + - const: -20000000 > > > > > > > > > > > > + - const: 20000000 > > > > > > > > > > > > + > > > > > > > > > > > > + required: > > > > > > > > > > > > + - reg > > > > > > > > > > > > + > > > > > > > > > > > > + additionalProperties: false > > > > > > > > > > > > + > > > > > > > > > > > > +required: > > > > > > > > > > > > + - compatible > > > > > > > > > > > > + - reg > > > > > > > > > > > > + - vdd-supply > > > > > > > > > > > > + - avdd-supply > > > > > > > > > > > > + - hvdd-supply > > > > > > > > > > > > + > > > > > > > > > > > > +dependencies: > > > > > > > > > > > > + spi-cpha: [ spi-cpol ] > > > > > > > > > > > > + spi-cpol: [ spi-cpha ] > > > > > > > > > > > > + > > > > > > > > > > > > +allOf: > > > > > > > > > > > > + - $ref: /schemas/spi/spi-peripheral-props.yaml# > > > > > > > > > > > > + > > > > > > > > > > > > +unevaluatedProperties: false > > > > > > > > > > > > + > > > > > > > > > > > > +examples: > > > > > > > > > > > > + - | > > > > > > > > > > > > + #include > > > > > > > > > > > > + > > > > > > > > > > > > + spi { > > > > > > > > > > > > + #address-cells = <1>; > > > > > > > > > > > > + #size-cells = <0>; > > > > > > > > > > > > + > > > > > > > > > > > > + dac@0 { > > > > > > > > > > > > + compatible = "adi,ad5529r-16"; > > > > > > > > > > > > + reg = <0>; > > > > > > > > > > > > + spi-max-frequency = <25000000>; > > > > > > > > > > > > + > > > > > > > > > > > > + vdd-supply = <&vdd_regulator>; > > > > > > > > > > > > + avdd-supply = <&avdd_regulator>; > > > > > > > > > > > > + hvdd-supply = <&hvdd_regulator>; > > > > > > > > > > > > + hvss-supply = <&hvss_regulator>; > > > > > > > > > > > > + > > > > > > > > > > > > + reset-gpios = <&gpio0 87 GPIO_ACTIVE_LOW>; > > > > > > > > > > > > + > > > > > > > > > > > > + #address-cells = <1>; > > > > > > > > > > > > + #size-cells = <0>; > > > > > > > > > > > > + > > > > > > > > > > > > + channel@0 { > > > > > > > > > > > > + reg = <0>; > > > > > > > > > > > > + adi,output-range-microvolt = <0 5000000>; > > > > > > > > > > > > + }; > > > > > > > > > > > > + > > > > > > > > > > > > + channel@1 { > > > > > > > > > > > > + reg = <1>; > > > > > > > > > > > > + adi,output-range-microvolt = <(-10000000) 10000000>; > > > > > > > > > > > > + }; > > > > > > > > > > > > + > > > > > > > > > > > > + channel@2 { > > > > > > > > > > > > + reg = <2>; > > > > > > > > > > > > + adi,output-range-microvolt = <0 40000000>; > > > > > > > > > > > > + }; > > > > > > > > > > > > + }; > > > > > > > > > > > > + }; > > > > > > > > > > > ... > > > > > > > > > > > > > > > > > > > > > > spi { > > > > > > > > > > > #address-cells = <1>; > > > > > > > > > > > #size-cells = <0>; > > > > > > > > > > > > > > > > > > > > > > multi-dac@0 { > > > > > > > > > > > compatible = "adi,ad5529r-16"; > > > > > > > > > > > reg = <0>; > > > > > > > > > > > spi-max-frequency = <25000000>; > > > > > > > > > > > > > > > > > > > > > > #address-cells = <1>; > > > > > > > > > > > #size-cells = <0>; > > > > > > > > > > > > > > > > > > > > > > dac@0 { > > > > > > > > > > > reg = <0>; > > > > > > > > > > > vdd-supply = <&vdd_regulator>; > > > > > > > > > > > avdd-supply = <&avdd_regulator>; > > > > > > > > > > > hvdd-supply = <&hvdd_regulator>; > > > > > > > > > > > hvss-supply = <&hvss_regulator>; > > > > > > > > > > > > > > > > > > > > > > reset-gpios = <&gpio0 87 GPIO_ACTIVE_LOW>; > > > > > > > > > > > > > > > > > > > > > > #address-cells = <1>; > > > > > > > > > > > #size-cells = <0>; > > > > > > > > > > > > > > > > > > > > > > channel@0 { > > > > > > > > > > > reg = <0>; > > > > > > > > > > > adi,output-range-microvolt = <0 5000000>; > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > channel@1 { > > > > > > > > > > > reg = <1>; > > > > > > > > > > > adi,output-range-microvolt = <(-10000000) 10000000>; > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > channel@2 { > > > > > > > > > > > reg = <2>; > > > > > > > > > > > adi,output-range-microvolt = <0 40000000>; > > > > > > > > > > > }; > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > dac@1 { > > > > > > > > > > > reg = <1>; > > > > > > > > > > > vdd-supply = <&vdd_regulator>; > > > > > > > > > > > avdd-supply = <&avdd_regulator>; > > > > > > > > > > > hvdd-supply = <&hvdd_regulator>; > > > > > > > > > > > hvss-supply = <&hvss_regulator>; > > > > > > > > > > > > > > > > > > > > > > reset-gpios = <&gpio0 88 GPIO_ACTIVE_LOW>; > > > > > > > > > > > > > > > > > > > > > > #address-cells = <1>; > > > > > > > > > > > #size-cells = <0>; > > > > > > > > > > > > > > > > > > > > > > channel@0 { > > > > > > > > > > > reg = <0>; > > > > > > > > > > > adi,output-range-microvolt = <0 5000000>; > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > channel@1 { > > > > > > > > > > > reg = <1>; > > > > > > > > > > > adi,output-range-microvolt = <(-10000000) 10000000>; > > > > > > > > > > > }; > > > > > > > > > > > } > > > > > > > > > > > }; > > > > > > > > > > > }; > > > > > > > > > > > > > > > > > > > > > > then you might need something like: > > > > > > > > > > > > > > > > > > > > > > patternProperties: > > > > > > > > > > > "^dac@[0-3]$": > > > > > > > > > > > > > > > > > > > > > > and put most of the things under this node pattern. > > > > > > > > > > > > > > > > > > > > > > So the main driver that you're putting together might need to handle up to four instances. > > > > > > > > > > > Even if your current driver cannot handle this, the dt-bindings might need cover that. > > > > > > > > > > > > > > > > > > > > > > Need to double check if each dac node needs a separate compatible, so you would maybe populate > > > > > > > > > > > a platform data to be shared with the child nodes, which would be a separate driver. > > > > > > > > > > > (not sure if it would make sense to mix and match ad5529r-16 and ad5529r-12). > > > > > > > > > > Hi Rodrigo, > > > > > > > > > > > > > > > > > > > > Thank you for looking at this. > > > > > > > > > > > > > > > > > > > > For now, I would prefer to keep the binding scoped to a single AD5529R device instance. The current > > > > > > > > > > hardware/use case we have only needs one device node and the driver is written around that model as well. > > > > > > > > > > While the device addressing pins could allow multi-device topology, we do not have an actual platform using > > > > > > > > > > that configuration at the moment, so I would prefer not to introduce an extra parent/child binding structure > > > > > > > > > > speculatively without a validating use case. > > > > > > > > > Interesting feature - kind of similar to address control on a typical i2c bus device, or > > > > > > > > > looking at it another way a kind of distributed SPI mux. > > > > > > > > > > > > > > > > > > Challenge of a binding is we need to anticipate the future. So I think we do need something > > > > > > > > > like Rodrigo is suggesting even if we only (for now) support a single instance in the driver. > > > > > > > > > That would leave the path open to supporting the addressing at a later date. > > > > > > > > > An alternative might be to look at it like a chained device setup. In those we pretend there > > > > > > > > > is just one device with a lot of channels etc. The snag is that here things are more loosely > > > > > > > > > coupled whereas for those devices it tends to be you have to read / write the same register > > > > > > > > > in all devices in the chain as one big SPI message. > > > > > > > > > > > > > > > > > > +CC Mark Brown as he may know of some precedence for this feature. For his reference.. > > > > > > > > > - Each of these device has 2 ID pins. The SPI transfers have to contain the 2 bit > > > > > > > > > value that matches that or they are ignored. Thus a single bus + 1 chip select can > > > > > > > > > be used to talk to 4 devices. Question is what that looks like in device tree + I guess > > > > > > > > > longer term how to support it cleanly in SPI. > > > > > > > > > > > > > > I'd swear I have seen this before, from some Microchip devices. Let me > > > > > > > see if I can find what I am thinking of... > > > > > > > > > > > > > > > > > > microchip,mcp3911 and microchip,mcp3564 both seem to do this with > > > > > > slightly different properties. > > > > > > > > > > > > microchip,device-addr: > > > > > > description: Device address when multiple MCP3911 chips are present on the same SPI bus. > > > > > > $ref: /schemas/types.yaml#/definitions/uint32 > > > > > > enum: [0, 1, 2, 3] > > > > > > default: 0 > > > > > > > > > > > > and > > > > > > > > > > > > > > > > > > microchip,hw-device-address: > > > > > > $ref: /schemas/types.yaml#/definitions/uint32 > > > > > > minimum: 0 > > > > > > maximum: 3 > > > > > > description: > > > > > > The address is set on a per-device basis by fuses in the factory, > > > > > > configured on request. If not requested, the fuses are set for 0x1. > > > > > > The device address is part of the device markings to avoid > > > > > > potential confusion. This address is coded on two bits, so four possible > > > > > > addresses are available when multiple devices are present on the same > > > > > > SPI bus with only one Chip Select line for all devices. > > > > > > Each device communication starts by a CS falling edge, followed by the > > > > > > clocking of the device address (BITS[7:6] - top two bits of COMMAND BYTE > > > > > > which is first one on the wire). > > > > > > > > > > > > This sounds exactly like the sort of feature that you're dealing with > > > > > > here? > > > > > > > > > > > > > > > > The core idea yes but for this chip, things are a bit more annoying (but > > > > > Janani can correct me if I'm wrong). Here, each device can, in theory, > > > > > have it's own supplies, pins and at the very least, channels with maybe > > > > > different scales. That is why Janani is proposing dac nodes. Given I > > > > > honestly don't like much of that "adi,ad5529r-bus" compatible I wondered > > > > > about solving this at the spi level. > > > > > > > > > > Ah and to make it more annoying, we can also mix 12 and 16 bits variants > > > > > together in the same bus. > > > > > > > > I'm definitely missing something, because that property for the > > > > microchip devices is not impacted what else is on the bus. AFAICT, you > > > > could have an mcp3911 and an mcp3564 on the same bus even though both > > > > are completely different devices with different drivers. They have > > > > individual device nodes and their own supplies etc etc. These aren't > > > > per-channel properties on an adc or dac, they're per child device on a > > > > spi bus. > > > > > > Maybe I'm the one missing something :). IIRC, spi would not allow two > > > devices on the same CS right? Because for this chip we would need > > > something like: > > > > > > spi { > > > dac@0 { > > > reg = <0>; > > > adi,pin-id = <0>; > > > }; > > > > > > dac@1 { > > > reg = <0>; // which seems already problematic? > > > adi,pin-id <1>; > > > }; > > > > > > ... > > > > > > //up to 4 > > > }; > > Yeah. It's not clear to me how that works for the microchip devices > > (I suspect it doesn't!) > > > > Just thinking as I type, but could we do something a bit nasty with > > a gpio mux that doesn't actually switch but represents the GPIO being > > shared? Given this is all tied to the spi bus that should all happen > > under serializing locks. > > > > Agreed though that this would be nicer as an SPI thing that let > > us specify that a single CS is share by multiple devices and their > > is some other signal acting to select which one we are talking to. > > > > If the device-addressing on the same chip-select is to be handled > by the spi framework, wouldn't we lose device-specific features? > > I understand that this multi-device feature is there mostly to extend the > channel count from 16 to 32, 48 or 64. I suppose the command: > > "MULTI DEVICE SW LDAC MODE" > > exists so that software can update channel values accross multiple devices. Right! You do have a point! I agree the main driver for a feature like this is likely to extend the channel count and effectively "aggregate" devices. But I would say that even with the spi solution the MULTI DEVICE stuff should be doable (as we still need a sort of adi,pin-id property). But yes, I do feel that the whole feature is for aggregation so seeing one device with 32 channels is the expectation here? Rather than seeing two devices with 16 channels. - Nuno Sá > > -- > Kind regards, > > Rodrigo Alencar