linux-kernel - Re: [PATCH v2 1/2] dt-bindings: phy: phy-stm32-usbphyc: add #clock-cells required property

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Message-ID: <be0f4e5f-3e7d-d178-160b-ea90e9e00147@foss.st.com>
Date:   Tue, 26 Jan 2021 10:49:29 +0100
From:   Amelie DELAUNAY <amelie.delaunay@...s.st.com>
To:     Rob Herring <robh@...nel.org>
CC:     Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH v2 1/2] dt-bindings: phy: phy-stm32-usbphyc: add
 #clock-cells required property

Hi Rob,

On 1/25/21 10:40 PM, Rob Herring wrote:
> On Thu, Jan 14, 2021 at 06:13:13PM +0100, Amelie Delaunay wrote:
>> usbphyc provides a unique clock called ck_usbo_48m.
>> STM32 USB OTG needs a 48Mhz clock (utmifs_clk48) for Full-Speed operation.
>> ck_usbo_48m is a possible parent clock for USB OTG 48Mhz clock.
>>
>> ck_usbo_48m is available as soon as the PLL is enabled.
>>
>> Signed-off-by: Amelie Delaunay <amelie.delaunay@...s.st.com>
>> ---
>> No change in v2.
>> ---
>>   .../devicetree/bindings/phy/phy-stm32-usbphyc.yaml          | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/phy-stm32-usbphyc.yaml b/Documentation/devicetree/bindings/phy/phy-stm32-usbphyc.yaml
>> index 46df6786727a..4e4da64b8e01 100644
>> --- a/Documentation/devicetree/bindings/phy/phy-stm32-usbphyc.yaml
>> +++ b/Documentation/devicetree/bindings/phy/phy-stm32-usbphyc.yaml
>> @@ -51,6 +51,10 @@ properties:
>>     vdda1v8-supply:
>>       description: regulator providing 1V8 power supply to the PLL block
>>   
>> +  '#clock-cells':
>> +    description: number of clock cells for ck_usbo_48m consumer
>> +    const: 0
>> +
>>   #Required child nodes:
>>   
>>   patternProperties:
>> @@ -102,6 +106,7 @@ required:
>>     - "#size-cells"
>>     - vdda1v1-supply
>>     - vdda1v8-supply
>> +  - '#clock-cells'
> 
> You can't really make new properties required as it's not backwards
> compatible. If things can never work without or the binding has never
> been used, then you can. You just need to spell this out in the commit
> msg.
> 

In fact things can work without this property. But I made this new 
property required because in clock-bindings, #clock-cells property is a 
required property for clock providers.

phy-stm32-usbphyc bindings are only used in stm32mp151.dtsi, which will 
be updated with this new property as soon as this bindings will be reviewed.

I can remove this new property from required ones, but is it okay as 
#clock-cells property is a required property for clock providers?

Regards,
Amelie

>>     - usb-phy@0
>>     - usb-phy@1
>>   
>> @@ -120,6 +125,7 @@ examples:
>>           vdda1v8-supply = <&reg18>;
>>           #address-cells = <1>;
>>           #size-cells = <0>;
>> +        #clock-cells = <0>;
>>   
>>           usbphyc_port0: usb-phy@0 {
>>               reg = <0>;
>> -- 
>> 2.17.1
>>