Re: [PATCH v5 1/2] dt-bindings: serial: Document WK2xxx SPI UART

[Conor Dooley <conor@kernel.org>]

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On Fri, Oct 09, 2026 at 04:24:07PM +0800, zjzhao@edatec.cn wrote:
> From: Zi Jie Zhao <zjzhao@edatec.cn>
> 
> Add a DT binding for the WK2xxx SPI-to-UART bridge ICs (WK2124,
> WK2132, WK2168, WK2212 and WK2204) from Chengdu Weikai
> Microelectronics (WKmic).
> 
> Describe each UART channel with a serial@N child node carrying its
> serial and RS-485 properties. Register the wkmic vendor prefix based
> on the vendor website.
> 
> Differentiate compatible strings by channel count and register
> availability. WK2124 and WK2132 lack hardware flow-control and
> RS-485 registers. WK2212 is a separate two-channel model that
> supports both features. Reject serial@2 and serial@3 on the
> two-channel members.
> 
> Correct the WK2202 compatible used in the public v4 series to
> WK2212. WK2202 in the public reference driver is a typo.
> 
> Require the standard clocks property for the single external
> reference clock used by the chips.
> 
> Assisted-by: LLM
> Signed-off-by: Zi Jie Zhao <zjzhao@edatec.cn>
> ---
>  .../bindings/serial/wkmic,wk2124.yaml         | 119 ++++++++++++++++++
>  .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
>  MAINTAINERS                                   |   7 ++
>  3 files changed, 128 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
> 
> diff --git a/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml b/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
> new file mode 100644
> index 000000000000..47a0cbdb5ca1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
> @@ -0,0 +1,119 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/serial/wkmic,wk2124.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: WKmic WK2xxx SPI to UART bridge
> +
> +maintainers:
> +  - Huang Yang <hy@wkmic.com>
> +
> +description:
> +  The WK2xxx family (WK2124, WK2132, WK2168, WK2212 and WK2204) are SPI to
> +  UART bridge ICs from WKmic (Chengdu Weikai Microelectronics). Each IC
> +  exposes two or four full-duplex UART channels with 256-byte RX/TX FIFOs
> +  through a single SPI slave interface and one interrupt line, and is
> +  clocked from a single external reference clock. Each channel is
> +  described by a "serial@N" child node that carries its own serial and
> +  RS-485 properties.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - wkmic,wk2124
> +      - wkmic,wk2132
> +      - wkmic,wk2168
> +      - wkmic,wk2212
> +      - wkmic,wk2204
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    description:
> +      When missing, the device driver uses polling instead.
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +patternProperties:
> +  "^serial@[0-3]$":
> +    type: object
> +    description: A single UART channel of the chip.
> +    allOf:
> +      - $ref: /schemas/serial/serial.yaml#
> +      - $ref: /schemas/serial/rs485.yaml#
> +    properties:
> +      reg:
> +        description: UART channel number on the chip.
> +        maximum: 3
> +    required:
> +      - reg
> +    unevaluatedProperties: false
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - wkmic,wk2132
> +              - wkmic,wk2212
> +    then:
> +      patternProperties:
> +        "^serial@[23]$": false
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    xtal: clock-11059200 {
> +        compatible = "fixed-clock";
> +        clock-frequency = <11059200>;
> +        #clock-cells = <0>;
> +    };

Drop this node here please, the infra will populate it at runtime to
make your example work.

pw-bot: changes-requested

Otherwise, it looks fine.to me..

Thanks,
Conor.


> +
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        serial@0 {
> +            compatible = "wkmic,wk2204";
> +            reg = <0>;
> +            spi-max-frequency = <10000000>;
> +            clocks = <&xtal>;
> +            interrupt-parent = <&gpio>;
> +            interrupts = <24 IRQ_TYPE_LEVEL_LOW>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            serial@0 {
> +                reg = <0>;
> +            };
> +
> +            serial@1 {
> +                reg = <1>;
> +                rs485-rts-active-low;
> +                linux,rs485-enabled-at-boot-time;
> +            };
> +        };
> +    };
> diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml
> index ba2002969373..cdc04229d642 100644
> --- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
> +++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
> @@ -1907,6 +1907,8 @@ patternProperties:
>      description: Wireless Tag (qiming yunduan)
>    "^wits,.*":
>      description: Shenzhen Merrii Technology Co., Ltd. (WITS)
> +  "^wkmic,.*":
> +    description: Chengdu Weikai Microelectronics Co., Ltd. (http://www.wkmic.com/)
>    "^wlf,.*":
>      description: Wolfson Microelectronics
>    "^wm,.*":
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3b2eb2a7a89a..e4a2443524d4 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -29432,6 +29432,13 @@ M:	Miloslav Trmac <mitr@volny.cz>
>  S:	Maintained
>  F:	drivers/input/misc/wistron_btns.c
>  
> +WK2XXX SPI UART DRIVER
> +M:	Huang Yang <hy@wkmic.com>
> +L:	linux-serial@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
> +F:	drivers/tty/serial/wk2xxx.c
> +
>  WMI BINARY MOF DRIVER
>  M:	Armin Wolf <W_Armin@gmx.de>
>  R:	Thomas Weißschuh <linux@weissschuh.net>
> -- 
> 2.43.0
> 

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