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: <3157e5a7-19f3-404c-8842-3f1942de03d7@linaro.org>
Date: Tue, 27 Jan 2026 15:26:05 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Geert Uytterhoeven <geert@...ux-m68k.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

On 1/27/26 15:02, Geert Uytterhoeven wrote:
> 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...

Well electronically the IC requires those voltages

> 
>>
>>>
>>>> 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 ;-)...

but you're right, I'll mark them required...

> 
>>>> +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?

... and add them to example.

>>>
>>>> +        };
>>>> +    };
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 

Thanks,
Neil