netdev - Re: [PATCH v2 2/4] dt-bindings: net: qcom: Add binding for shared mdio bus

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Date:   Mon, 17 Sep 2018 09:54:29 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     "Wang, Dongsheng" <dongsheng.wang@...-semitech.com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     "timur@...nel.org" <timur@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Zheng, Joey" <yu.zheng@...-semitech.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] dt-bindings: net: qcom: Add binding for shared
 mdio bus

On 09/17/2018 09:47 AM, Wang, Dongsheng wrote:
> On 9/17/2018 10:50 PM, Andrew Lunn wrote:
>> On Mon, Sep 17, 2018 at 04:53:29PM +0800, Wang Dongsheng wrote:
>>> This property copy from "ibm,emac.txt" to describe a shared MIDO bus.
>>> Since emac include MDIO, so If the motherboard has more than one PHY
>>> connected to an MDIO bus, this property will point to the MAC device
>>> that has the MDIO bus.
>>>
>>> Signed-off-by: Wang Dongsheng <dongsheng.wang@...-semitech.com>
>>> ---
>>> V2: s/Since QDF2400 emac/Since emac/
>>> ---
>>>  Documentation/devicetree/bindings/net/qcom-emac.txt | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/qcom-emac.txt b/Documentation/devicetree/bindings/net/qcom-emac.txt
>>> index 346e6c7f47b7..50db71771358 100644
>>> --- a/Documentation/devicetree/bindings/net/qcom-emac.txt
>>> +++ b/Documentation/devicetree/bindings/net/qcom-emac.txt
>>> @@ -24,6 +24,9 @@ Internal PHY node:
>>>  The external phy child node:
>>>  - reg : The phy address
>>>  
>>> +Optional properties:
>>> +- mdio-device : Shared MIDO bus.
>> Hi Dongsheng
>>
>> I don't see why you need this property. The ethernet interface has a
>> phy-handle which points to a PHY. That is all you need to find the PHY.
> phy-handle is description PHY address. This property is describing an
> MDIO controller.
> Each QCOM emac include an MDIO controller, normally each emac only
> connect one
> PHY device, but when all of the PHY devices mdio lines connect one MDIO
> controller
> that is included in EMAC, we need to share this MDIO controller for
> others EMAC.

If you want to describe the MDIO controller, then you embed a mdio
subnode into your Ethernet MAC node:

 emac0: ethernet@...20000 {
	mdio {
		#address-cells = <1>;
		#size-cells = <0>;

		phy0: ethernet-phy@0 {
			reg = <0>;
		};
	};
};

And then each Ethernet MAC controller refers to their appropriate PHY
device tree node using a phy-handle property to point to either their
own MDIO controller, or another MAC's MDIO controller.

The IBM Emac is a old (not to say bad) example and it does not use the
PHY library and the standard Device Tree node property, please don't use
it as a reference.
-- 
Florian