linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: Add T-HEAD TH1520 USB controller

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Message-ID: <ZR2Tl1rkRdIG+fQa@xhacker>
Date:   Thu, 5 Oct 2023 00:32:23 +0800
From:   Jisheng Zhang <jszhang@...nel.org>
To:     Samuel Holland <samuel.holland@...ive.com>
Cc:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Guo Ren <guoren@...nel.org>,
        Fu Wei <wefu@...hat.com>, linux-riscv@...ts.infradead.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH 1/2] dt-bindings: usb: Add T-HEAD TH1520 USB controller

On Wed, Sep 27, 2023 at 03:00:59PM -0500, Samuel Holland wrote:
> On 2023-09-27 11:42 AM, Jisheng Zhang wrote:
> > T-HEAD TH1520 platform's USB has a wrapper module around
> > the DesignWare USB3 DRD controller. Add binding information doc for
> > it.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> > ---
> >  .../bindings/usb/thead,th1520-usb.yaml        | 73 +++++++++++++++++++
> >  1 file changed, 73 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/usb/thead,th1520-usb.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/usb/thead,th1520-usb.yaml b/Documentation/devicetree/bindings/usb/thead,th1520-usb.yaml
> > new file mode 100644
> > index 000000000000..afb618eb5013
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/usb/thead,th1520-usb.yaml
> > @@ -0,0 +1,73 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/usb/thead,th1520-usb.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: T-HEAD TH1520 DWC3 USB Controller Glue
> > +
> > +maintainers:
> > +  - Jisheng Zhang <jszhang@...nel.org>
> > +
> > +properties:
> > +  compatible:
> > +    const: thead,th1520-usb
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    maxItems: 4
> > +
> > +  clock-names:
> > +    items:
> > +      - const: ref
> > +      - const: bus_early
> > +      - const: phy
> > +      - const: suspend
> 
> Except for "phy", these clocks are already documented in snps,dwc3.yaml. Are
> they necessary for the glue/PHY, or do they belong only in the controller node?

Hi Samuel,

Enabling ref, bus_early clks are necessary for the glue layer, because
we program the glue registers before calling of_platform_populate()

> They are not used by the driver in patch 2. Also, the PHY clock probably belongs
> with the PHY node.

Except enabling the phy clk, we don't need to touch the phy, so I'm not
sure how to handle this if we have a dedicated phy driver thus a phy node.
or use the usb-nop-xceiv?

Thanks
> 
> > +
> > +  ranges: true
> > +
> > +  '#address-cells':
> > +    enum: [ 1, 2 ]
> > +
> > +  '#size-cells':
> > +    enum: [ 1, 2 ]
> > +
> > +# Required child node:
> > +
> > +patternProperties:
> > +  "^usb@[0-9a-f]+$":
> > +    $ref: snps,dwc3.yaml#
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +  - ranges
> > +
> > +additionalProperties: false
> 
> The driver in patch 2 uses the thead,misc-sysreg and vbus-supply properties,
> neither of which is documented here. Also, depending on the other bindings, the
> VBUS supply should be referenced from the USB PHY or connector node, not here.
> 
> Regards,
> Samuel
> 
> > +examples:
> > +  - |
> > +
> > +    usb {
> > +          compatible = "thead,th1520-usb";
> > +          reg = <0xec03f000 0x1000>;
> > +          clocks = <&clk 1>,
> > +                   <&clk 2>,
> > +                   <&clk 3>,
> > +                   <&clk 4>;
> > +          clock-names = "ref", "bus_early", "phy", "suspend";
> > +          ranges;
> > +          #address-cells = <1>;
> > +          #size-cells = <1>;
> > +
> > +          usb@...40000 {
> > +                compatible = "snps,dwc3";
> > +                reg = <0xe7040000 0x10000>;
> > +                interrupts = <68>;
> > +                dr_mode = "host";
> > +          };
> > +    };
>