netdev - Re: [PATCH] [v7] net: emac: emac gigabit ethernet controller driver

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Date:	Wed, 17 Aug 2016 21:04:37 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Timur Tabi <timur@...eaurora.org>, Al Stone <al.stone@...aro.org>,
	Rob Herring <robh@...nel.org>
CC:	netdev <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	Sagar Dharia <sdharia@...eaurora.org>,
	Shanker Donthineni <shankerd@...eaurora.org>,
	Vikram Sethi <vikrams@...eaurora.org>,
	Christopher Covington <cov@...eaurora.org>,
	Gilad Avidov <gavidov@...eaurora.org>,
	Andrew Lunn <andrew@...n.ch>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Mark Langsdorf <mlangsdo@...hat.com>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Andy Gross <agross@...eaurora.org>,
	David Miller <davem@...emloft.net>,
	Lino Sanfilippo <LinoSanfilippo@....de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Abdulhamid, Harb" <harba@...eaurora.org>
Subject: Re: [PATCH] [v7] net: emac: emac gigabit ethernet controller driver

On August 17, 2016 8:27:19 PM PDT, Timur Tabi <timur@...eaurora.org> wrote:
>Florian Fainelli wrote:
>
>>>      emac_sgmii: ethernet-phy@...400 {
>>>          compatible = "qcom,qdf2432-emac-phy";
>>>          reg = <0x0 0x00410400 0x0 0x100>;
>>>          interrupts = <0 0x104 0>;
>>>      };
>>>
>>
>> Is this register range relative to the emac0 node here, or is this
>> really a separate node, within the same adress space as your emac0
>node?
>
>It's a separate node within the same address space.  We can't guarantee
>
>that it's adjacent to any other EMAC register -- it could be anywhere
>in 
>memory. 0x00410400 is the real physical address of those registers.

Ok

>
>> Answer largely depends on whether your device is really located
>outside
>> of the emac, if it located outside, then a platform device matching
>the
>> compatible string would get you what you want. If the emac_sgmii
>block
>> is a sub-block within the EMAC, then a few things need fixing:
>>
>> - your emac_sgmii node should be a sub-node of the emac node, not a
>sibling
>> - the emac0 node should have a "ranges" property that indicates how
>to
>> translate the sub-nodes' "reg" property based on the base register
>> address of the emac0 block
>> - you would have to call of_platform_populate from the EMAC driver to
>> ensure that the emac_sgmii child node and therefore platform device
>gets
>> created
>
>Even if the emac_sgmii block were a sub-block, wouldn't it conflict
>with 
>the ethernet-phy@4 node?  The #address-cells and #size-cells properties
>
>cannot be valid for both the emac_sgmii and ethernet-phy@4 nodes.

These two properties apply to subnodes within the emac0 and emac_sgmii nodes, this is standard DT stuff here.

The larger issue is that the emac_sgmii node in the form you posted is going to be backed by a platform device in Linux while you want a PHY device with a reg property that describes a MDIO address (#address-cells = 1, #size-cells = 0). 

IIRC the amd xgbe driver mainline had a similar design but still implemented a PHY device anyway although it may not have been using Device Tree. It should still be possible to implement a PHY driver that you manually register and bind to its device_node pointer such that of_phy_find_device and friends still work. You would do this from the emac_sgmii platform device driver and parent devices in a way that satisfy the PHY device driver lifecycle as well.

Hope this helps.

NB: another way to do this is to give the SGMII PHY device a MDIO address, provided that it has one, and you pass the memory mapped register range as a syscon property pointing to the emac_sgmii register range. This is not really clean through.


-- 
Florian