linux-kernel - Re: [PATCH 1/2] dt-bindings: net: fsl,fec: Add TX clock controls

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Date:   Thu, 13 Jul 2023 10:47:02 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Vesa Jääskeläinen 
        <vesa.jaaskelainen@...sala.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     devicetree@...r.kernel.org, Conor Dooley <conor+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Russell King <linux@...linux.org.uk>,
        Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Shenwei Wang <shenwei.wang@....com>,
        Clark Wang <xiaoning.wang@....com>,
        NXP Linux Team <linux-imx@....com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jakub Kicinski <kuba@...nel.org>, Wei Fang <wei.fang@....com>,
        netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        Shawn Guo <shawnguo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] dt-bindings: net: fsl,fec: Add TX clock controls

Hello Vesa,

On 13.07.23 10:29, Vesa Jääskeläinen wrote:
> Hi Krzysztof,
> 
> On 12.7.2023 23.36, Krzysztof Kozlowski wrote:
>> On 11/07/2023 17:08, Vesa Jääskeläinen wrote:
>>> With fsl,fec-tx-clock-output one can control if TX clock is routed outside
>>> of the chip.
>>>
>>> With fsl,fec-tx-clk-as-ref-clock one can select if external TX clock is as
>>> reference clock.
>>>
>>> Signed-off-by: Vesa Jääskeläinen <vesa.jaaskelainen@...sala.com>
>>> ---
>>>   .../devicetree/bindings/net/fsl,fec.yaml          | 15 +++++++++++++++
>>>   1 file changed, 15 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/fsl,fec.yaml b/Documentation/devicetree/bindings/net/fsl,fec.yaml
>>> index b494e009326e..c09105878bc6 100644
>>> --- a/Documentation/devicetree/bindings/net/fsl,fec.yaml
>>> +++ b/Documentation/devicetree/bindings/net/fsl,fec.yaml
>>> @@ -166,6 +166,21 @@ properties:
>>>       description:
>>>         If present, indicates that the hardware supports waking up via magic packet.
>>>   +  fsl,fec-tx-clock-output:
>>> +    $ref: /schemas/types.yaml#/definitions/flag
>>> +    description:
>>> +      If present, ENETx_TX_CLK output driver is enabled.
>>> +      If not present, ENETx_TX_CLK output driver is disabled.
>> Here...
>>
>>> +
>>> +  fsl,fec-tx-clk-as-ref-clock:
>>> +    $ref: /schemas/types.yaml#/definitions/flag
>>> +    description:
>>> +      If present, gets ENETx TX reference clk from the ENETx_TX_CLK pin. In
>>> +      this use case, an external OSC provides the clock for both the external
>>> +      PHY and the internal controller.
>>> +      If not present, ENETx TX reference clock is driven by ref_enetpllx. This
>>> +      clock is also output to pins via the IOMUX.ENET_REF_CLKx function.
>> and here:
>> In general, Common Clock Framework and its bindings should be used for
>> handling clock providers and consumers. Why it cannot be used for these
>> two cases?
> 
> Did you have something specific in mind on how it could be modeled?
> 
> I tried to look at:
> Documentation/devicetree/bindings/clock/
> 
> But didn't spot anything for this.

This has been implemented for i.MX6Q/DL using CCF. Please follow suit
for SoloX. See series at:
https://lore.kernel.org/all/20230131084642.709385-1-o.rempel@pengutronix.de/

Thanks,
Ahmad



> 
> In net bindings:
> Documentation/devicetree/bindings/net
> 
> We have some similarities:
> 
> - adi,phy-output-clock
> - adi,phy-output-reference-clock
> - nxp,rmii-refclk-in
> - clock_in_out
> - ti,clk-output-sel
> - ti,sgmii-ref-clock-output-enable
> 
> In here clock output generator would be the i.MX not the PHY as what was in ADI's.
> 
> xMII variants are close but very specific for specific MII interface type.
> 
> clock_in_out seems a bit out of place.
> 
> Thanks,
> Vesa Jääskeläinen
> 
> 
> 

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