netdev - Re: [PATCH 2/4] dt-bindings: add binding for RTL8211E Ethernet PHY

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Date:   Fri, 05 May 2017 02:10:50 +0800
From:   icenowy@...c.io
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Rob Herring <robh+dt@...nel.org>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-sunxi@...glegroups.com, Icenowy Zheng <icenowy@...c.xyz>
Subject: Re: [PATCH 2/4] dt-bindings: add binding for RTL8211E Ethernet PHY

在 2017-04-22 08:22，Florian Fainelli 写道：
> On 04/21/2017 04:24 PM, Icenowy Zheng wrote:
>> From: Icenowy Zheng <icenowy@...c.xyz>
>> 
>> Some RTL8211E Ethernet PHY have an issue that needs a workaround
>> indicated with device tree.
>> 
>> Add the binding for a property that indicates this workaround.
>> 
>> Signed-off-by: Icenowy Zheng <icenowy@...c.xyz>
>> ---
>>  .../devicetree/bindings/net/realtek,rtl8211e.txt   | 22 
>> ++++++++++++++++++++++
>>  1 file changed, 22 insertions(+)
>>  create mode 100644 
>> Documentation/devicetree/bindings/net/realtek,rtl8211e.txt
>> 
>> diff --git 
>> a/Documentation/devicetree/bindings/net/realtek,rtl8211e.txt 
>> b/Documentation/devicetree/bindings/net/realtek,rtl8211e.txt
>> new file mode 100644
>> index 000000000000..c1913301bfe8
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/net/realtek,rtl8211e.txt
>> @@ -0,0 +1,22 @@
>> +Realtek RTL8211E Ethernet PHY
>> +
>> +One batch of RTL8211E is slight broken, that needs some special (and
>> +full of magic numbers) tweaking in order to make GbE to operate 
>> properly.
>> +The only well-known board that used the broken batch is Pine64+.
>> +Configure it through an Ethernet OF device node.
>> +
>> +Optional properties:
>> +
>> +- realtek,disable-rx-delay:
>> +  If set, RX delay will be completely disabled (according to 
>> Realtek). This
>> +  will affect the performance on non-broken boards.
>> +  default: do not disable RX delay.
> 
> Please don't introduce custom properties to do that, instead correct
> specify the "phy-mode" such that it is e.g: "rgmii-txid" which 
> indicates
> that there should be no RX internal delay, but a TX internal delay 
> added
> by the PHY.

Checked the document, the meaning of "rgmii-txid" is not correct here.

This doesn't effect the MAC, and the MAC should still add TX delay.

The definition of "rgmii-txid" in
Documentation/devicetree/binding/net/ethernet.txt is "RGMII with
internal TX delay provided by the PHY, the MAC should not add an TX 
delay
in this case". However, this do not indicate that the MAC doesn't add TX
delay; in fact that just totally disabled the PHY to provide the RX 
delay.
MAC still should to add delay on both TX/RX, which is the semantic of
standard "rgmii".

So I cannot used "rgmii-txid" here, but should continue to use this
custom property.