linux-kernel - Re: [PATCH RFC net-next 2/3] dt-bindings: net: mscc-miim: add clock and clock-frequency

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Message-ID: <3d4159d6-112a-7818-8192-7197dcfca894@linaro.org>
Date:   Thu, 31 Mar 2022 22:30:30 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Michael Walle <michael@...le.cc>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net-next 2/3] dt-bindings: net: mscc-miim: add clock
 and clock-frequency

On 31/03/2022 22:16, Andrew Lunn wrote:
> On Thu, Mar 31, 2022 at 10:05:48PM +0200, Krzysztof Kozlowski wrote:
>> On 31/03/2022 17:14, Michael Walle wrote:
>>> Add the (optional) clock input of the MDIO controller and indicate that
>>> the common clock-frequency property is supported. The driver can use it
>>> to set the desired MDIO bus frequency.
>>>
>>> Signed-off-by: Michael Walle <michael@...le.cc>
>>> ---
>>>  Documentation/devicetree/bindings/net/mscc,miim.yaml | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/mscc,miim.yaml b/Documentation/devicetree/bindings/net/mscc,miim.yaml
>>> index b52bf1732755..e9e8ddcdade9 100644
>>> --- a/Documentation/devicetree/bindings/net/mscc,miim.yaml
>>> +++ b/Documentation/devicetree/bindings/net/mscc,miim.yaml
>>> @@ -32,6 +32,11 @@ properties:
>>>  
>>>    interrupts: true
>>>  
>>> +  clocks:
>>> +    maxItems: 1
>>> +
>>> +  clock-frequency: true
>>
>> This looks unusual clock-frequency is usually for clock providers but
>> this is a consumer, so it is not a common frequency here. You mention
>> that "driver can use it", so it's not a hardware description but some
>> feature for the driver. We have this already - use assigned-clock* in
>> your DTS.
> 
> Please see
> 
> Documentation/devicetree/bindings/net/mdio.yaml
> 
>   clock-frequency:
>     description:
>       Desired MDIO bus clock frequency in Hz. Values greater than IEEE 802.3
>       defined 2.5MHz should only be used when all devices on the bus support
>       the given clock speed.
> 
> The MDIO bus master provides the MDIO bus clock, so in a sense, the
> device is a provider. although it does also make use of the clock
> itself. It is a hardware description, because the users of the bus
> make use of the clock, i.e. the PHY devices on the bus.
> 
> It is also identical to i2c bus masters
> Documentation/devicetree/bindings/i2c/i2c.txt says:
> 

Thanks, it's good. Indeed buses also use this property.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof