linux-kernel - Re: [PATCH v3 05/12] dt-bindings: phy: renesas,usb2-phy: Add renesas,sysc-signals

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Message-ID: <b22e7a46-7e35-4840-aae3-a855c97fbde4@tuxon.dev>
Date: Thu, 22 May 2025 13:26:15 +0300
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: vkoul@...nel.org, kishon@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, p.zabel@...gutronix.de, geert+renesas@...der.be,
 magnus.damm@...il.com, yoshihiro.shimoda.uh@...esas.com, kees@...nel.org,
 gustavoars@...nel.org, biju.das.jz@...renesas.com,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-hardening@...r.kernel.org, john.madieu.xa@...renesas.com,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3 05/12] dt-bindings: phy: renesas,usb2-phy: Add
 renesas,sysc-signals

Hi, Krzysztof,

On 22.05.2025 10:03, Krzysztof Kozlowski wrote:
> On Wed, May 21, 2025 at 05:09:36PM GMT, Claudiu wrote:
>>  .../bindings/phy/renesas,usb2-phy.yaml        | 22 +++++++++++++++++++
>>  1 file changed, 22 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/renesas,usb2-phy.yaml b/Documentation/devicetree/bindings/phy/renesas,usb2-phy.yaml
>> index 12f8d5d8af55..e1e773cba847 100644
>> --- a/Documentation/devicetree/bindings/phy/renesas,usb2-phy.yaml
>> +++ b/Documentation/devicetree/bindings/phy/renesas,usb2-phy.yaml
>> @@ -86,6 +86,16 @@ properties:
>>  
>>    dr_mode: true
>>  
>> +  renesas,sysc-signals:
>> +    description: System controller phandle, specifying the register
>> +      offset and bitmask associated with a specific system controller signal
> 
> This is 100% redundant information. system controller specifying system
> controller signal.
> 
> Drop.
> 
> 
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +    items:
>> +      - items:
>> +          - description: system controller phandle
> 
> What for? Explain the usage. How is ut used by this hardware.

OK, I though I've explained in the renesas,sysc-signals description
section. I'll adjust it and move it here.

> 
>> +          - description: register offset associated with a signal
> 
> What signal? That's a phy.

Would you like me to specify here exactly the signal name? I tried to made
it generic as the system controller provides other signals to other IPs,
the intention was to use the same property for other IPs, if any. And kept
it generic in the idea it could be used in future, if any, for other
signals provided by the system controller to the USB PHY.

As explained in the commit description, on the Renesas RZ/G3S SoC, the USB
PHY receives a signal from the system controller that need to be
de-asserted/asserted when power is turned on/off. This signal, called
PWRRDY, is controlled through a specific register in the system controller
memory space.

With this property the intention is to specify to the USB PHY driver the
phandle to the SYSC, register offset within SYSC address space in charge of
controlling the USB PWRRDY signal and the bitmask within this register.

The PHY driver parse this information and set the signal at proper moments.

> 
>> +          - description: register bitmask associated with a signal
>> +
>>  if:
>>    properties:
>>      compatible:
>> @@ -117,6 +127,18 @@ allOf:
>>        required:
>>          - resets
>>  
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            const: renesas,usb2-phy-r9a08g045
>> +    then:
>> +      required:
>> +        - renesas,sysc-signals
> 
> That's ABI break.

There is no in kernel device tree users of "renesas,usb2-phy-r9a08g045"
compatible. It is introduced in patch 11/12 from this series. With this do
you still consider it ABI break?

Thank you for your review,
Claudiu