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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
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