linux-kernel - Re: [PATCH net-next v2 3/4] dt-bindings: net: Add RGMII internal delay for DP83869

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Date:   Wed, 20 May 2020 10:30:19 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <f.fainelli@...il.com>, <hkallweit1@...il.com>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v2 3/4] dt-bindings: net: Add RGMII internal
 delay for DP83869

Andrew

On 5/20/20 10:28 AM, Dan Murphy wrote:
> Andrew
>
> On 5/20/20 8:56 AM, Andrew Lunn wrote:
>> On Wed, May 20, 2020 at 07:18:34AM -0500, Dan Murphy wrote:
>>> Add the internal delay values into the header and update the binding
>>> with the internal delay properties.
>>>
>>> Signed-off-by: Dan Murphy <dmurphy@...com>
>>> ---
>>>   .../devicetree/bindings/net/ti,dp83869.yaml    | 16 ++++++++++++++++
>>>   include/dt-bindings/net/ti-dp83869.h           | 18 
>>> ++++++++++++++++++
>>>   2 files changed, 34 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/ti,dp83869.yaml 
>>> b/Documentation/devicetree/bindings/net/ti,dp83869.yaml
>>> index 5b69ef03bbf7..344015ab9081 100644
>>> --- a/Documentation/devicetree/bindings/net/ti,dp83869.yaml
>>> +++ b/Documentation/devicetree/bindings/net/ti,dp83869.yaml
>>> @@ -64,6 +64,20 @@ properties:
>>>          Operational mode for the PHY.  If this is not set then the 
>>> operational
>>>          mode is set by the straps. see dt-bindings/net/ti-dp83869.h 
>>> for values
>>>   +  ti,rx-internal-delay:
>>> +    $ref: /schemas/types.yaml#definitions/uint32
>>> +    description: |
>>> +      RGMII Receive Clock Delay - see dt-bindings/net/ti-dp83869.h
>>> +      for applicable values. Required only if interface type is
>>> +      PHY_INTERFACE_MODE_RGMII_ID or PHY_INTERFACE_MODE_RGMII_RXID.
>> Hi Dan
>>
>> Having it required with PHY_INTERFACE_MODE_RGMII_ID or
>> PHY_INTERFACE_MODE_RGMII_RXID is pretty unusual. Normally these
>> properties are used to fine tune the delay, if the default of 2ns does
>> not work.
>
> Also if the MAC phy-mode is configured with RGMII-ID and no internal 
> delay values defined wouldn't that be counter intuitive?
>
> The driver will error out if the RGMII-ID is used and there was no 
> internal delay defined for either rx or tx making either one required.
>
> The MAC node needs to indicate to use the internal delay for RGMII 
> other wise the driver should ignore the internal delay programming as 
> these internal delays are not applicable to SGMII or MII modes.  The 
> RGMII mode can be used if the default 2ns delay is acceptable.
>
> Thus why we are documenting in the binding when the internal delay is 
> required as putting these under "required" is not correct.
>
> Dan
>
This is also the same for the DP83867 PHY as that PHY and the 83869 have 
a few identical features like internal delay, WoL and downshifting.

Dan


>>
>>      Andrew