Re: [PATCH v3 1/2] dt-bindings: phy: Add Rockchip MIPI CSI/DSI PHY schema

["Heiko Stübner" <heiko@sntech.de>]

Am Freitag, 22. November 2024, 19:49:20 CET schrieb Sebastian Reichel:
> Hi,
> 
> On Wed, Nov 13, 2024 at 11:10:17PM +0100, Heiko Stuebner wrote:
> > From: Heiko Stuebner <heiko.stuebner@cherry.de>
> > 
> > Add dt-binding schema for the MIPI CSI/DSI PHY found on
> > Rockchip RK3588 SoCs.
> > 
> > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> > Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
> > ---
> >  .../phy/rockchip,rk3588-mipi-dcphy.yaml       | 82 +++++++++++++++++++
> >  1 file changed, 82 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml b/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
> > new file mode 100644
> > index 000000000000..5ee8d7246fa0
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
> > @@ -0,0 +1,82 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/phy/rockchip,rk3588-mipi-dcphy.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Rockchip MIPI CSI/DSI PHY with Samsung IP block
> > +
> > +maintainers:
> > +  - Guochun Huang <hero.huang@rock-chips.com>
> > +  - Heiko Stuebner <heiko@sntech.de>
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - rockchip,rk3576-mipi-dcphy
> > +      - rockchip,rk3588-mipi-dcphy
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  "#phy-cells":
> > +    const: 0
> 
> I would expect an argument to select between D-PHY and C-PHY mode,
> so that the binding is ready for it even when the driver does not
> yet support it. E.g. something like
> 
>   '#phy-cells':
>     const: 1
>     description: |
>       Supported modes are:
>         - PHY_TYPE_DPHY
>         - PHY_TYPE_CPHY
>       See include/dt-bindings/phy/phy.h for constants.
> 
> This would match how it works for the naneng Combo PHY to switch
> between PCIe/SATA/USB3. Also Mediatek CSI DC-PHY handles it that
> way upstream (with just D-PHY being supported). I see that the
> driver stack you send upstream expects, that the PHY user (e.g.
> the DSI controller) instead manually calls phy_set_mode(phy, <mode>).
> To me it seems more sensible to just get this automaically from DT.

The mode-selection for the phy is definitly tied to the hardware-design.
Depending on how the board is designed, it'll always do either D-PHY
or C-PHY mode.

I guess it mostly just feels strange when so far the parameter was
used to identify say an individual clock from the clock controller.

But reading the Medietek discussion (up to [0]) it looks like that is
a nice way to do this, so I'll adapt things in the next version.


Heiko


[0] https://lore.kernel.org/all/20230608200552.GA3303349-robh@kernel.org/


> Otherwise the whole series LGTM.
> 
> Greetings,
> 
> -- Sebastian
> 
> > +  clocks:
> > +    maxItems: 2
> > +
> > +  clock-names:
> > +    items:
> > +      - const: pclk
> > +      - const: ref
> > +
> > +  resets:
> > +    maxItems: 4
> > +
> > +  reset-names:
> > +    items:
> > +      - const: m_phy
> > +      - const: apb
> > +      - const: grf
> > +      - const: s_phy
> > +
> > +  rockchip,grf:
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +    description:
> > +      Phandle to the syscon managing the 'mipi dcphy general register files'.
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +  - resets
> > +  - reset-names
> > +  - "#phy-cells"
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/rockchip,rk3588-cru.h>
> > +    #include <dt-bindings/reset/rockchip,rk3588-cru.h>
> > +
> > +    soc {
> > +      #address-cells = <2>;
> > +      #size-cells = <2>;
> > +
> > +      phy@feda0000 {
> > +        compatible = "rockchip,rk3588-mipi-dcphy";
> > +        reg = <0x0 0xfeda0000 0x0 0x10000>;
> > +        clocks = <&cru PCLK_MIPI_DCPHY0>,
> > +                 <&cru CLK_USBDPPHY_MIPIDCPPHY_REF>;
> > +        clock-names = "pclk", "ref";
> > +        resets = <&cru SRST_M_MIPI_DCPHY0>,
> > +                 <&cru SRST_P_MIPI_DCPHY0>,
> > +                 <&cru SRST_P_MIPI_DCPHY0_GRF>,
> > +                 <&cru SRST_S_MIPI_DCPHY0>;
> > +        reset-names = "m_phy", "apb", "grf", "s_phy";
> > +        rockchip,grf = <&mipidcphy0_grf>;
> > +        #phy-cells = <0>;
> > +      };
> > +    };
>