Re: [PATCH v3 1/4] dt-bindings: usb: dwc3-xilinx: Add MMI USB support on Versal Gen2 platform

[Pandey, Radhey Shyam]

> On Wed, Apr 29, 2026 at 11:00:47PM +0530, Radhey Shyam Pandey wrote:
> >   additionalProperties: false
> >   
> >   examples:
> > @@ -156,3 +193,30 @@ examples:
> >               };
> >           };
> >       };
> > +  - |
> > +    #include <dt-bindings/power/xlnx-zynqmp-power.h>
> > +    #include <dt-bindings/reset/xlnx-zynqmp-resets.h>
> > +    #include <dt-bindings/phy/phy.h>
> > +    usb {
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> Please follow DTS coding style.
Thanks for the review. will fix it in next version.
> > +        compatible = "xlnx,versal2-mmi-dwc3";
> I really doubt that DWC3 block comes without addressing space
> (registers), so either you just misrepresented things, like created a
> fake block and syscon, or forgot to combine DWC3 with the wrapper.
>
> And if you built with W=1 your DTS you would see errors. How do you see
> it now? Where do you place it? Wrapper must be outside of soc, but DWC3
> child must be inside. Did you read submitting patches and writing
> bindings documents?
Apologies for missing the DTS sanity check earlier. I am summarizing the
problem statement and possible solution. Please review.

For MMI USB in current implementation it need a parent/child
representation. However, the parent IP is shared across DP, USB,
and HDCP, so it cannot have a USB-dedicated parent reg space.

1. Versal platform
  - Parent: USB wrapper IP → has its own I/O space
  - Child: USB DWC3

2. Versal Gen2 platform - MMI USB
  - Parent subsystem combines DP, USB, and HDCP in a single I/O space
  - Children:
    - USB DWC3
    - DP
    - HDCP

To model the Versal Gen2 MMI USB parent register space, I introduced
xlnx,usb-syscon, allowing the DWC3 driver to access parent registers
via a syscon handle, addressing the v1 review comment.

However, making reg optional satisfies schema validation but fails
DTB checks.

versal2.dtsi:1: Warning (simple_bus_reg):
/axi/mmi-usb: missing or empty reg/ranges property

To fix it i think we can switch from parent/child representation to
flat DT representation for the Versal Gen2 platform, similar to
existing implementations in qcom,snps-dwc3 and Google Tensor G5 DWC3
bindings[1].

The Google Tensor DWC3 binding uses a syscon phandle to access USB
configuration registers, which aligns well with the Versal Gen2 MMI
USB IP, where wrapper subsystem shares a common register space for
USB along with other IPs.

If this approach looks fine , will create binding for MMI USB using
this flat representation and send out next version.

usb@fe200000 {
compatible = "xlnx,versal2-mmi-dwc3";
reg = <0xfe200000 0x40000>;
xlnx,usb-syscon = <&udh_slcr 0x005c 0x0070 0x00c4 0x00f8>;
<snip>
};

[1]: 32bc790a8e49 dt-bindings: usb: dwc3: Add Google Tensor G5 DWC3
> > +        clocks = <&zynqmp_clk 32>, <&zynqmp_clk 34>;
> > +        clock-names = "bus_clk", "ref_clk";
> > +        power-domains = <&zynqmp_firmware PD_USB_0>;
> > +        resets = <&zynqmp_reset ZYNQMP_RESET_USB1_CORERESET>;
> > +        reset-names = "usb_crst";
> > +        phys = <&psgtr 2 PHY_TYPE_USB3 0 2>;
> > +        phy-names = "usb3-phy";
> > +        xlnx,usb-syscon = <&udh_slcr 0x005c 0x0070 0x00c4 0x00f8>;
> > +        ranges;
> > +
> > +        usb@fe200000 {
> > +            compatible = "snps,dwc3";
> > +            reg = <0xfe200000 0x40000>;
> > +            interrupt-names = "host", "otg";
> > +            interrupts = <0 65 4>, <0 69 4>;
> Why these are not proper defines?

will fix it in next version.

> > +            dr_mode = "host";
> > +            dma-coherent;
> > +        };
> > +    };
> > --
> > 2.43.0