linux-kernel - Re: [PATCH v2 1/7] dt-bindings: usb: document the Renesas UPD720201/UPD720202 USB 3.0 xHCI Host Controller

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Message-ID: <CAMuHMdV=u280N2HUgpiHtRXuMv0RhtDeEFDaSLFQ0Wg8frt+6A@mail.gmail.com>
Date: Tue, 27 Jan 2026 15:02:16 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Rob Clark <robin.clark@....qualcomm.com>, 
	Dmitry Baryshkov <lumag@...nel.org>, Abhinav Kumar <abhinav.kumar@...ux.dev>, 
	Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Bartosz Golaszewski <brgl@...nel.org>, Manivannan Sadhasivam <mani@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-usb@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v2 1/7] dt-bindings: usb: document the Renesas
 UPD720201/UPD720202 USB 3.0 xHCI Host Controller

Hi Neil,

On Tue, 27 Jan 2026 at 14:55, Neil Armstrong <neil.armstrong@...aro.org> wrote:
> On 1/27/26 11:20, Geert Uytterhoeven wrote:
> > On Tue, 27 Jan 2026 at 10:57, Neil Armstrong <neil.armstrong@...aro.org> wrote:
> >> Document the Renesas UPD720201/UPD720202 USB 3.0 xHCI Host Controller,
> >> which connects over PCIe and requires specific power supplies to
> >
> > Here: "requires"...
>
> Sorry I don't understand

Please read below the continuations ("...") below...

>
> >
> >> start up.
> >>
> >> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>

> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/usb/renesas,upd720201-pci.yaml
> >> @@ -0,0 +1,55 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/usb/renesas,upd720201-pci.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: UPD720201/UPD720202 USB 3.0 xHCI Host Controller (PCIe)
> >> +
> >> +maintainers:
> >> +  - Neil Armstrong <neil.armstrong@...aro.org>
> >> +
> >> +description:
> >> +  UPD720201 USB 3.0 xHCI Host Controller via PCIe x1 Gen2 interface.
> >> +  The UPD720202 up to two downstream ports, while UPD720201 supports up to
> >> +  four downstream USB 3.0 rev1.0 ports.
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: pci1912,0014
> >
> > Just wondering: how does having a new driver
> > drivers/pci/pwrctrl/pci-pwrctrl-upd720201.c matching against this
> > compatible play well with normal PCI discovery and probing of
> > drivers/usb/host/xhci-pci-renesas.c?
>
> In Linux, power control is implemented as a platform device driver,
> so it doesn't collide with the pci driver.
>
> The pci driver won't probe until the device shows up on the bus anyway,
> so he power control will attach as platform for this purpose.

OK.

> >> +  avdd33-supply:
> >> +    description: +3.3 V power supply for analog circuit
> >> +
> >> +  vdd10-supply:
> >> +    description: +1.05 V power supply
> >> +
> >> +  vdd33-supply:
> >> +    description: +3.3 V power supply
> >> +
> >> +required:
> >> +  - compatible
> >> +  - reg
> >
> > ... but no power supplies are listed here? ...
>
> None are stricly required, they can be supplied directly without
> a passive regulator. Not sure they should be required

So the goal of this binding is to document the required power supplies
which are not required? I am confused (but that could just be me ;-)...

> >> +examples:
> >> +  - |
> >> +    pcie@0 {
> >> +        reg = <0x0 0x1000>;
> >> +        ranges = <0x02000000 0x0 0x100000 0x10000000 0x0 0x0>;
> >> +        #address-cells = <3>;
> >> +        #size-cells = <2>;
> >> +        device_type = "pci";
> >> +
> >> +        usb@0 {
> >
> > The actual DTS uses "usb-controller".
> >
> >> +            compatible = "pci1912,0014";
> >> +            reg = <0x0 0x0 0x0 0x0 0x0>;
> >
> > ... also not in the example?
> >
> >> +        };
> >> +    };

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds