[PATCH v4 4/5] dt-bindings: phy: realtek: Add the doc about the Realtek SoC USB 2.0 PHY

[Krzysztof Kozlowski]

On 14/06/2023 11:28, Stanley Chang wrote:
> Add the documentation explain the property about Realtek USB PHY driver.
> 
> Realtek DHC (digital home center) RTD SoCs support DWC3 XHCI USB
> controller. Added the driver to drive the USB 2.0 PHY transceivers.
> 
> Signed-off-by: Stanley Chang <stanley_chang at realtek.com>
> ---
> v3 to v4 change:
>     1. Remove the parameter and non hardware properties from dts.
>     2. Using the compatible data included the config and parameter
>        in driver.
> v2 to v3 change:
>     1. Broken down into two patches, one for each of USB 2 & 3.
>     2. Add more description about Realtek RTD SoCs architecture.
>     3. Removed parameter v1 support for simplification.
>     4. Revised the compatible name for fallback compatible.
>     5. Remove some properties that can be set in the driver.
> v1 to v2 change:
>     Add phy-cells for generic phy driver
> ---
>  .../bindings/phy/realtek,usb2phy.yaml         | 145 ++++++++++++++++++
>  1 file changed, 145 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/phy/realtek,usb2phy.yaml
> 
> diff --git a/Documentation/devicetree/bindings/phy/realtek,usb2phy.yaml b/Documentation/devicetree/bindings/phy/realtek,usb2phy.yaml
> new file mode 100644
> index 000000000000..cfd77143475c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/phy/realtek,usb2phy.yaml
> @@ -0,0 +1,145 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright 2023 Realtek Semiconductor Corporation
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/phy/realtek,usb2phy.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Realtek DHC SoCs USB 2.0 PHY
> +
> +maintainers:
> +  - Stanley Chang <stanley_chang at realtek.com>
> +
> +description:
> +  Realtek USB 2.0 PHY support the digital home center (DHC) RTD series SoCs.
> +  The USB 2.0 PHY driver is designed to support the XHCI controller. The SoCs
> +  support multiple XHCI controllers. One PHY device node maps to one XHCI
> +  controller.
> +
> +  RTD1295/RTD1619 SoCs USB
> +  The USB architecture includes three XHCI controllers.
> +  Each XHCI maps to one USB 2.0 PHY and map one USB 3.0 PHY on some
> +  controllers.
> +  XHCI controller#0 -- usb2phy -- phy#0
> +                    |- usb3phy -- phy#0
> +  XHCI controller#1 -- usb2phy -- phy#0
> +  XHCI controller#2 -- usb2phy -- phy#0
> +                    |- usb3phy -- phy#0
> +
> +  RTD1395 SoCs USB
> +  The USB architecture includes two XHCI controllers.
> +  The controller#0 has one USB 2.0 PHY. The controller#1 includes two USB 2.0
> +  PHY.
> +  XHCI controller#0 -- usb2phy -- phy#0
> +  XHCI controller#1 -- usb2phy -- phy#0
> +                               |- phy#1
> +
> +  RTD1319/RTD1619b SoCs USB
> +  The USB architecture includes three XHCI controllers.
> +  Each XHCI maps to one USB 2.0 PHY and map one USB 3.0 PHY on controllers#2.
> +  XHCI controller#0 -- usb2phy -- phy#0
> +  XHCI controller#1 -- usb2phy -- phy#0
> +  XHCI controller#2 -- usb2phy -- phy#0
> +                    |- usb3phy -- phy#0
> +
> +  RTD1319d SoCs USB
> +  The USB architecture includes three XHCI controllers.
> +  Each xhci maps to one USB 2.0 PHY and map one USB 3.0 PHY on controllers#0.
> +  XHCI controller#0 -- usb2phy -- phy#0
> +                    |- usb3phy -- phy#0
> +  XHCI controller#1 -- usb2phy -- phy#0
> +  XHCI controller#2 -- usb2phy -- phy#0
> +
> +  RTD1312c/RTD1315e SoCs USB
> +  The USB architecture includes three XHCI controllers.
> +  Each XHCI maps to one USB 2.0 PHY.
> +  XHCI controller#0 -- usb2phy -- phy#0
> +  XHCI controller#1 -- usb2phy -- phy#0
> +  XHCI controller#2 -- usb2phy -- phy#0
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - realtek,rtd1295-usb2phy
> +          - realtek,rtd1312c-usb2phy
> +          - realtek,rtd1315e-usb2phy
> +          - realtek,rtd1319-usb2phy
> +          - realtek,rtd1319d-usb2phy
> +          - realtek,rtd1395-usb2phy
> +          - realtek,rtd1395-usb2phy-2port
> +          - realtek,rtd1619-usb2phy
> +          - realtek,rtd1619b-usb2phy
> +      - const: realtek,usb2phy

That's not what your driver is saying... This patchset has random set of
changes.

I suggest to drop "realtek,usb2phy".

> +
> +  reg:
> +    items:
> +      - description: PHY data registers
> +      - description: PHY control registers
> +
> +  "#phy-cells":
> +    const: 0
> +
> +  nvmem-cells:
> +    maxItems: 2
> +    description:
> +      Phandles to nvmem cell that contains the trimming data.
> +      If unspecified, default value is used.
> +
> +  nvmem-cell-names:
> +    items:
> +      - const: usb-dc-cal
> +      - const: usb-dc-dis
> +    description:
> +      The following names, which correspond to each nvmem-cells.
> +      usb-dc-cal is the driving level for each phy specified via efuse.
> +      usb-dc-dis is the disconnection level for each phy specified via efuse.
> +
> +  realtek,inverse-hstx-sync-clock:
> +    description:
> +      For one of the phys of RTD1619b SoC, the synchronous clock of the
> +      high-speed tx must be inverted. So this property is used to set the
> +      inverted clock.

Drop last sentence, it is redundant.

> +    type: boolean
> +
> +  realtek,driving-level:
> +    description:
> +      Each board or port may have a different driving capability. This
> +      will adjust the driving level value if the value is not the default.

I don't understand it. What is "driving capability" and if each port can
have it different, why do you need property for this?

You mention some default - why it is not expressed as "default: xx"?

What do the values mean?

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 31
> +
> +  realtek,driving-compensate:
> +    description:
> +      For RTD1315e SoC, the driving level can be adjusted by reading the
> +      efuse table. Therefore, this property provides drive compensation for
> +      different boards with different drive capabilities.

if driving level can be read from nvmem, why do you have
realtek,driving-level in the first place? Don't you miss here some allOf
making this constrained per variant?

"Therefore" means "for that reason" or "as a consequence". How is this
property a consequence of reading driving level from efuse? Is it then
mutually exclusive with "realtek,driving-level"? But your schema does
not express it.

> +    $ref: /schemas/types.yaml#/definitions/int32
> +    minimum: -8
> +    maximum: 8
> +
> +  realtek,disconnection-compensate:
> +    description:
> +      This adjusts the disconnection level compensation for the different
> +      boards with different disconnection level.
> +    $ref: /schemas/types.yaml#/definitions/int32
> +    minimum: -8
> +    maximum: 8
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#phy-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    usb_port0_usb2phy: usb-phy at 13214 {
> +        compatible = "realtek,rtd1319d-usb2phy", "realtek,usb2phy";
> +        reg = <0x13214 0x4>, <0x28280 0x4>;
> +        #phy-cells = <0>;
> +
> +        realtek,driving-level = <0xe>;

Why this example is so empty? You have at least 6 more properties which
should be shown here.

Best regards,
Krzysztof