Re: [PATCH v13 1/2] dt-bindings: phy: qcom: Add CSI2 C-PHY/DPHY schema

[Neil Armstrong]

Hi,

On 7/20/26 03:11, Bryan O'Donoghue wrote:
> Add a base schema for the MIPI CSI2 PHYs on Qualcomm SoCs. This PHY
> supports both DPHY and CPHY operation. A special mode of DPHY operation -
> called variously split-mode or combo-mode also allows for two sensors to be
> connected to one PHY.
>
> The submitted binding here describes the DPHY modes of operation only. CPHY
> is left to future work.
>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
> ---
>   .../bindings/phy/qcom,x1e80100-csi2-phy.yaml       | 195 +++++++++++++++++++++
>   1 file changed, 195 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/phy/qcom,x1e80100-csi2-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,x1e80100-csi2-phy.yaml
> new file mode 100644
> index 0000000000000..880fe602945cb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/phy/qcom,x1e80100-csi2-phy.yaml
> @@ -0,0 +1,195 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/phy/qcom,x1e80100-csi2-phy.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm X1E80100 SoC CSI2 PHY
> +
> +maintainers:
> +  - Bryan O'Donoghue <bod@xxxxxxxxxx>
> +
> +description:
> +  Qualcomm MIPI CSI2 C-PHY/D-PHY combination PHY. Connects MIPI CSI2 sensors
> +  to Qualcomm's Camera CSI Decoder. The PHY supports both C-PHY and D-PHY
> +  modes.
> +
> +properties:
> +  compatible:
> +    const: qcom,x1e80100-csi2-phy
> +
> +  reg:
> +    maxItems: 1
> +
> +  "#phy-cells":
> +    const: 1
> +    description:
> +      The single cell specifies the PHY operating mode.
> +
> +  clocks:
> +    maxItems: 3
> +
> +  clock-names:
> +    items:
> +      - const: core
> +      - const: timer
> +      - const: ahb
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  operating-points-v2: true
> +
> +  opp-table:
> +    type: object
> +
> +  power-domains:
> +    items:
> +      - description: Titan Top GDSC - Titan ISP Block, Global Distributed Switch Controller.
> +      - description: MMCX voltage rail
> +      - description: MXC or MXA voltage rail
> +
> +  power-domain-names:
> +    items:
> +      - const: top
> +      - const: mmcx
> +      - const: mx
> +
> +  vdda-0p9-supply:
> +    description: Phandle to a 0.9V regulator supply to a PHY.
> +
> +  vdda-1p2-supply:
> +    description: Phandle to 1.2V regulator supply to a PHY.
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        description:
> +          Sensor input. Always present. A single sensor is described by a
> +          single endpoint with one to four data lanes. DPHY split mode,
> +          where two independent sensors share the same PHY, is described
> +          by two endpoints; endpoint@0 with exactly two data-lanes and
> +          endpoint@1 with exactly one data-lane.
> +        unevaluatedProperties: false
> +
> +        patternProperties:
> +          "^endpoint(@[0-9a-f]+)?$":
> +            $ref: /schemas/media/video-interfaces.yaml#
> +            unevaluatedProperties: false
> +            properties:
> +              data-lanes:
> +                minItems: 1
> +                maxItems: 4
> +
> +            required:
> +              - data-lanes
> +              - remote-endpoint
> +
> +        allOf:
> +          - if:
> +              required:
> +                - endpoint@1
> +            then:
> +              properties:
> +                endpoint@0:
> +                  properties:
> +                    data-lanes:
> +                      minItems: 2
> +                      maxItems: 2
> +                endpoint@1:
> +                  properties:
> +                    data-lanes:
> +                      maxItems: 1
> +              required:
> +                - endpoint@0
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: Output to the CAMSS CSID controller.
> +
> +    required:
> +      - port@0
> +      - port@1
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#phy-cells"
> +  - clocks
> +  - clock-names
> +  - interrupts
> +  - operating-points-v2
> +  - power-domains
> +  - power-domain-names
> +  - vdda-0p9-supply
> +  - vdda-1p2-supply
> +  - ports
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/clock/qcom,x1e80100-camcc.h>
> +    #include <dt-bindings/clock/qcom,x1e80100-gcc.h>
> +    #include <dt-bindings/power/qcom,rpmhpd.h>
> +
> +    phy@ace4000 {
> +        compatible = "qcom,x1e80100-csi2-phy";
> +        reg = <0x0ace4000 0x2000>;
> +        #phy-cells = <1>;
> +
> +        clocks = <&camcc CAM_CC_CSIPHY0_CLK>,
> +                 <&camcc CAM_CC_CSI0PHYTIMER_CLK>,
> +                 <&camcc CAM_CC_CORE_AHB_CLK>;
> +        clock-names = "core",
> +                      "timer",
> +                      "ahb";
> +
> +        interrupts = <GIC_SPI 477 IRQ_TYPE_EDGE_RISING>;
> +
> +        operating-points-v2 = <&csiphy_opp_table>;
> +
> +        power-domains = <&camcc CAM_CC_TITAN_TOP_GDSC>,
> +                        <&rpmhpd RPMHPD_MMCX>,
> +                        <&rpmhpd RPMHPD_MX>;
> +        power-domain-names = "top",
> +                             "mmcx",
> +                             "mx";
> +
> +        vdda-0p9-supply = <&vreg_l2c_0p9>;
> +        vdda-1p2-supply = <&vreg_l1c_1p2>;
> +
> +        ports {
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            port@0 {
> +                reg = <0>;
> +                csiphy0_in: endpoint {
> +                    data-lanes = <0 1 2 3>;
> +                    remote-endpoint = <&sensor_out>;
> +                };
> +            };
> +
> +            port@1 {
> +                reg = <1>;
> +                csiphy0_out: endpoint {
> +                    remote-endpoint = <&csid_in>;
> +                };
> +            };
> +        };
> +
> +        csiphy_opp_table: opp-table {
> +            compatible = "operating-points-v2";
> +
> +            opp-300000000 {
> +                opp-hz = /bits/ 64 <300000000>;
> +                required-opps = <&rpmhpd_opp_low_svs_d1>,
> +                                <&rpmhpd_opp_low_svs_d1>;
> +            };
> +        };
> +    };

While I see the utility of moving the CSI PHY into a separate node and
transferring the sensor endpoints there, I don't see why the PHYs would
be linked to CAMSS via the `phys =` property and via a port/endpoint to the CSIDs.

In my view, the `phys =` property should be used to reference static PHYs
associated with a controller, whereas port/endpoint graphs are better suited
for identifying the node and device for dynamic PHYs, like the ones we have here.

To that extent, I understand how moving this to the PHY framework could help
clean up the code. However, some PHY-related logic will still need to remain in
CAMSS to handle dynamic associations to different CSIDs at runtime.

I'm still not really convinced about moving this code to the PHY subsystem
as a standalone PHY driver.

Neil