linux-kernel - Re: [PATCH net-next v7 1/6] dt-bindings: net: Add tx and rx internal delays

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Message-ID: <71943ef1-3e64-47a9-2027-ad801795bdf5@ti.com>
Date:   Thu, 18 Jun 2020 08:44:12 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <f.fainelli@...il.com>, <hkallweit1@...il.com>,
        <davem@...emloft.net>, <robh@...nel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v7 1/6] dt-bindings: net: Add tx and rx internal
 delays

Andrew

On 6/17/20 9:01 PM, Andrew Lunn wrote:
> On Wed, Jun 17, 2020 at 01:20:14PM -0500, Dan Murphy wrote:
>> tx-internal-delays and rx-internal-delays are a common setting for RGMII
>> capable devices.
>>
>> These properties are used when the phy-mode or phy-controller is set to
>> rgmii-id, rgmii-rxid or rgmii-txid.  These modes indicate to the
>> controller that the PHY will add the internal delay for the connection.
>>
>> Signed-off-by: Dan Murphy <dmurphy@...com>
>> ---
>>   .../devicetree/bindings/net/ethernet-phy.yaml         | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>> index 9b1f1147ca36..b2887476fe6a 100644
>> --- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>> +++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>> @@ -162,6 +162,17 @@ properties:
>>       description:
>>         Specifies a reference to a node representing a SFP cage.
>>   
>> +
>> +  rx-internal-delay-ps:
>> +    description: |
>> +      RGMII Receive PHY Clock Delay defined in pico seconds.  This is used for
>> +      PHY's that have configurable RX internal delays.
>> +
>> +  tx-internal-delay-ps:
>> +    description: |
>> +      RGMII Transmit PHY Clock Delay defined in pico seconds.  This is used for
>> +      PHY's that have configurable TX internal delays.
>> +
> So in a later patch you have:
>
> default: 2000
>
> That seems to apply that these values only apply when the phy mode
> indicates a delay is needed. It would be good to document that here,
> when each of these properties will be used. Also, that they default to
> 2000 when not present.

The default of 2000ps is for the DP83869 only.  The DP83822 fixed delay 
is 3500ps.

So indicating that the default here is 2000ps for all devices is not 
correct.

But I can add a note that if these properties are present then the delay 
is added by the PHY.

Dan


>       Andrew