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: <6e8c3d6b-8cba-42da-bafa-28becfa15d60@linaro.org>
Date: Tue, 27 Jan 2026 14:55:36 +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

Hi,

On 1/27/26 11:20, Geert Uytterhoeven wrote:
> Hi Neil,
> 
> 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

> 
>> start up.
>>
>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>> ---
>>   .../bindings/usb/renesas,upd720201-pci.yaml        | 55 ++++++++++++++++++++++
>>   1 file changed, 55 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/renesas,upd720201-pci.yaml b/Documentation/devicetree/bindings/usb/renesas,upd720201-pci.yaml
>> new file mode 100644
>> index 000000000000..df3cdcf44747
>> --- /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.

> 
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  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

> 
>> +
>> +allOf:
>> +  - $ref: usb-xhci.yaml
>> +
>> +additionalProperties: false
>> +
>> +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?
> 
>> +        };
>> +    };
>>
>> --
>> 2.34.1
> 
> 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

Thanks,
Neil