linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: Add documentation for AM62 USB Wrapper module

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Date:   Wed, 23 Mar 2022 14:47:55 +0530
From:   Aswath Govindraju <a-govindraju@...com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, Felipe Balbi <balbi@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Roger Quadros <rogerq@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [PATCH 1/2] dt-bindings: usb: Add documentation for AM62 USB
 Wrapper module

Hi Krzysztof,

On 23/03/22 14:35, Krzysztof Kozlowski wrote:
> On 23/03/2022 06:35, Aswath Govindraju wrote:
>> Add bindings for the TI's AM62 wrapper module for the Synopsys USBSS-DRD
>> controller.
>>
>> Signed-off-by: Aswath Govindraju <a-govindraju@...com>
>> ---
>>  .../devicetree/bindings/usb/ti,am62-usb.yaml  | 98 +++++++++++++++++++
>>  1 file changed, 98 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/usb/ti,am62-usb.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/usb/ti,am62-usb.yaml b/Documentation/devicetree/bindings/usb/ti,am62-usb.yaml
>> new file mode 100644
>> index 000000000000..4bb139d1926d
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/usb/ti,am62-usb.yaml
>> @@ -0,0 +1,98 @@
>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/usb/ti,am62-usb.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Bindings for the TI's AM62 wrapper module for the Synopsys USBSS-DRD controller
> 
> Skip the "Bindings for the", just leave the HW description.
> 

Will drop it in the respin.

>> +
>> +maintainers:
>> +  - Aswath Govindraju <a-govindraju@...com>
>> +
>> +properties:
>> +  compatible:
>> +    const: ti,am62-usb
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  ranges: true
>> +
>> +  power-domains:
>> +    description:
>> +      PM domain provider node and an args specifier containing
>> +      the USB ISO device id value. See,
>> +      Documentation/devicetree/bindings/soc/ti/sci-pm-domain.yaml
>> +    maxItems: 1
>> +
>> +  clocks:
>> +    description: Clock phandles to usb2_refclk
>> +    maxItems: 1
>> +
>> +  clock-names:
>> +    items:
>> +      - const: ref
>> +
>> +  id-gpio:
>> +    description:
>> +      GPIO to be used as ID pin
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    description:
>> +      interrupt line to be used for detecting changes in VBUS
>> +
>> +  ti,vbus-divider:
>> +    description:
>> +      Should be present if USB VBUS line is connected to the
>> +      VBUS pin of the SoC via a 1/3 voltage divider.
>> +    type: boolean
>> +
>> +  ti,syscon-phy-pll-refclk:
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +    items:
>> +      - items:
>> +          - description: Phandle to the SYSCON entry
>> +          - description: USB phy control register offset within SYSCON
>> +    description: Specifier for configuring frequency of ref clock input.
> 
> This is a bit strange. The ref clock is the "ref" input clock, right? In
> such case use clk_set_rate()... Using syscon for managing clocks is not
> the proper way.
> 

The syscon property is not being used to set the ref clock frequency but
is rather being used to indicate the input clock frequency for USB PHY
operation. I think the description seems be misleading. I will update it
in the respin, to reflect the above description.

> Plus all the issues pointed out by Roger.
> 
>> +
>> +  '#address-cells':
>> +    const: 2
>> +
>> +  '#size-cells':
>> +    const: 2
> 
> No children allowed?
> 
> I understand this is a wrapper, which explains why you do not include
> usb-hcd.yaml schema. But since it is a wrapper, what is it wrapping?
> 

Yes, there is a child node, which would be the dwc3-contoller node.
Would adding the child node too in the example help capture this better?

>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - power-domains
>> +  - clocks
>> +  - clock-names
>> +  - interrupts
>> +  - ti,syscon-phy-pll-refclk
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/soc/ti,sci_pm_domain.h>
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    #include <dt-bindings/gpio/gpio.h>
>> +
>> +    bus {
>> +      #address-cells = <2>;
>> +      #size-cells = <2>;
>> +
>> +      dwc3-usb@...0000 {
> 
> Generic node name, so usb.
> 

Will correct this in the respin.


Thank you for the review.

>> +        compatible = "ti,am62-usb";
> 
> 
> Best regards,
> Krzysztof


-- 
Thanks,
Aswath