Re: [PATCH v5] dt-bindings: iio: adc: Convert xilinx-xadc bindings to YAML schema

From: Jonathan Cameron

Date: Sat Nov 07 2026 - 14:26:52 EST

On Sat, 7 Nov 2026 19:19:55 +0530
Dileep Kumar Nagavarapu <dileepkumar.nagavarapu@xxxxxxx> wrote:

> From: Pramod Maurya <pramod.nexgen@xxxxxxxxx>
>
> Convert the Xilinx XADC and UltraScale System Monitor device tree binding
> from the legacy plain-text format to a YAML.
>
> The new binding covers the same hardware and compatible strings:
> - xlnx,zynq-xadc-1.00.a (ZYNQ hardblock)
> - xlnx,axi-xadc-1.00.a (AXI softblock)
> - xlnx,system-management-wiz-1.3 (UltraScale System Management Wizard)
>
> The xlnx,channels subnode retains its legacy name (including the comma)
> for backwards compatibility with existing device trees.
>
> Move xlnx,channels under properties, as dt-schema now allows node names
> containing a comma for long-established bindings.Constrain the reg

Space after .

> property of the channel subnodes to the valid channel range of 0 to
> 16 with minimum and maximum.
>
> Drop the redundant "type: boolean" from xlnx,bipolar, since its $ref to
> the flag type already implies it.
>
> Signed-off-by: Pramod Maurya <pramod.nexgen@xxxxxxxxx>
> Co-developed-by: Dileep Kumar Nagavarapu <dileepkumar.nagavarapu@xxxxxxx>
> Signed-off-by: Dileep Kumar Nagavarapu <dileepkumar.nagavarapu@xxxxxxx>

Hi Dileep,

Given the legacy nature of the binding this looks fine to me.
I noted a few things on how I think it would look today, but not
expecting any changes to this doc based on those.

I do want an Ack from Lars-Peter Clausen though if we are going
to more formally list him as maintainer. No idea if he has time
to keep an eye on this one!

Jonathan

> ---
> .../bindings/iio/adc/xilinx-xadc.txt | 141 ---------------
> .../bindings/iio/adc/xlnx,xadc.yaml | 165 ++++++++++++++++++
> MAINTAINERS | 9 +
> 3 files changed, 174 insertions(+), 141 deletions(-)
> delete mode 100644 Documentation/devicetree/bindings/iio/adc/xilinx-xadc.txt
> create mode 100644 Documentation/devicetree/bindings/iio/adc/xlnx,xadc.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/xilinx-xadc.txt b/Documentation/devicetree/bindings/iio/adc/xilinx-xadc.txt
> deleted file mode 100644
> index f42e18078376..000000000000
> --- a/Documentation/devicetree/bindings/iio/adc/xilinx-xadc.txt
> +++ /dev/null

> diff --git a/Documentation/devicetree/bindings/iio/adc/xlnx,xadc.yaml b/Documentation/devicetree/bindings/iio/adc/xlnx,xadc.yaml
> new file mode 100644
> index 000000000000..2cbc3b82a26f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/xlnx,xadc.yaml
> @@ -0,0 +1,165 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/xlnx,xadc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xilinx XADC and UltraScale System Monitor
> +
> +maintainers:
> + - Lars-Peter Clausen <lars@xxxxxxxxxx>

As below. Need an Ack from Lars-Peter.

> + - Sai Krishna Potthuri <sai.krishna.potthuri@xxxxxxx>
> + - Dileep Kumar Nagavarapu <dileepkumar.nagavarapu@xxxxxxx>
> +
> +description: |
> + The Xilinx XADC is an ADC found in the Series 7 FPGAs. It has a DRP
> + (Dynamic Reconfiguration Port) interface for communication. Two different
> + frontends for the DRP interface are supported:
> +
> + - ZYNQ hardblock: available only on the ZYNQ family as a hardblock in
> + the SoC portion of the ZYNQ device.
> + - AXI softblock: available on all Series 7 platforms as a softblock
> + with an AXI interface (PG019).
> +
> + The Xilinx System Monitor is an ADC found in UltraScale and UltraScale+
> + FPGAs. It is accessed through the Xilinx System Management Wizard IP core
> + via an AXI interface in the FPGA fabric.
> +
> + The xlnx,channels subnode name contains a comma as part of the legacy
> + device tree binding that has been in use for over a decade. This name is
> + retained for backwards compatibility with existing device trees.
> +
> +properties:
> + compatible:
> + enum:
> + - xlnx,zynq-xadc-1.00.a
> + - xlnx,axi-xadc-1.00.a
> + - xlnx,system-management-wiz-1.3
> +
> + reg:
> + maxItems: 1
> +
> + interrupts:
> + maxItems: 1
> +
> + clocks:
> + maxItems: 1
> +
> + xlnx,external-mux:
> + $ref: /schemas/types.yaml#/definitions/string
> + description:
> + Selects the external multiplexer mode.
> + enum:
> + - none
> + - single
> + - dual
> + default: none
> +
> + xlnx,external-mux-channel:
> + $ref: /schemas/types.yaml#/definitions/uint32
> + description: |
> + Configures which pair of pins is used to sample data in external
> + multiplexer mode. Required when xlnx,external-mux is "single" or
> + "dual".

I guess this is a legacy binding, but if we were doing this today we'd
put an explicit mux consumer in front of it that makes use of the
channel via the io-channels consumer mapping stuff.
My guess is that stuff all came in well after this driver!

This is also rather inflexible as why can't we have a 4
channel mux that is therefore in front of 4 ADC channels?

> +
> + Valid values for single external multiplexer mode:
> + 0: VP/VN
> + 1: VAUXP[0]/VAUXN[0]
> + 2: VAUXP[1]/VAUXN[1]
> + ...
> + 16: VAUXP[15]/VAUXN[15]
> +
> + Valid values for dual external multiplexer mode:
> + 1: VAUXP[0]/VAUXN[0] - VAUXP[8]/VAUXN[8]
> + 2: VAUXP[1]/VAUXN[1] - VAUXP[9]/VAUXN[9]
> + ...
> + 8: VAUXP[7]/VAUXN[7] - VAUXP[15]/VAUXN[15]
> + minimum: 0
> + maximum: 16
> +
> + xlnx,channels:
> + type: object
> + description:
> + List of external channels connected to the ADC. If this node is
> + absent, no external channels are assumed to be connected.
> +
> + properties:
> + '#address-cells':
> + const: 1
> +
> + '#size-cells':
> + const: 0
> +
> + patternProperties:
> + "^channel@([0-9a-f]|10)$":
> + type: object
> + description:
> + Represents an external channel connected to the ADC.
> +
> + properties:
> + reg:
> + description: |
> + Pair of pins the channel is connected to.
> + 0: VP/VN
> + 1: VAUXP[0]/VAUXN[0]
> + 2: VAUXP[1]/VAUXN[1]
> + ...
> + 16: VAUXP[15]/VAUXN[15]

Another legacy one which is fine. If we were doing this today
we'd use diff-channels rather than reg to specify this I think.

> + minimum: 0
> + maximum: 16
> +
> + xlnx,bipolar:
> + $ref: /schemas/types.yaml#/definitions/flag
> + description:
> + If set, the channel is used in bipolar mode.
> +
> + required:
> + - reg
> +
> + additionalProperties: false
> +
> + required:
> + - '#address-cells'
> + - '#size-cells'
> +
> + additionalProperties: false
> +
> +allOf:
> + - if:
> + properties:
> + xlnx,external-mux:
> + enum:
> + - single
> + - dual
> + required:
> + - xlnx,external-mux
> + then:
> + required:
> + - xlnx,external-mux-channel
> +
> +required:
> + - compatible
> + - reg
> + - interrupts
> + - clocks
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + xadc@43200000 {
> + compatible = "xlnx,axi-xadc-1.00.a";
> + reg = <0x43200000 0x1000>;
> + interrupts = <0 53 4>;
> + interrupt-parent = <&gic>;
> + clocks = <&fpga1_clk>;
> +
> + xlnx,channels {
> + #address-cells = <1>;
> + #size-cells = <0>;
> + channel@0 {
> + reg = <0>;
> + xlnx,bipolar;
> + };
> + };
> + };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 745d8d0169b2..2d7e9c9ca659 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -29996,6 +29996,15 @@ F: Documentation/devicetree/bindings/watchdog/xlnx,xps-timebase-wdt.yaml
> F: drivers/watchdog/of_xilinx_wdt.c
> F: drivers/watchdog/xilinx_wwdt.c
>
> +XILINX XADC DRIVER
> +M: Lars-Peter Clausen <lars@xxxxxxxxxx>

I'll need an Ack from Lars-Peter for that. Whilst sometimes about
Lars isn't anywhere near as active as he once was.

> +M: Sai Krishna Potthuri <sai.krishna.potthuri@xxxxxxx>
> +M: Dileep Kumar Nagavarapu <dileepkumar.nagavarapu@xxxxxxx>
> +L: linux-iio@xxxxxxxxxxxxxxx
> +S: Maintained
> +F: Documentation/devicetree/bindings/iio/adc/xlnx,xadc.yaml
> +F: drivers/iio/adc/xilinx-xadc*