netdev - Re: [PATCH] net: fec: Add support for multiple phys on mdiobus

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Message-ID: <50FD22B4.5070307@openwrt.org>
Date:	Mon, 21 Jan 2013 12:12:52 +0100
From:	Florian Fainelli <florian@...nwrt.org>
To:	Wolfgang Grandegger <wg@...ndegger.com>
CC:	Sascha Hauer <s.hauer@...gutronix.de>, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, shawn.guo@...aro.org,
	davem@...emloft.net
Subject: Re: [PATCH] net: fec: Add support for multiple phys on mdiobus

On 01/21/2013 12:07 PM, Wolfgang Grandegger wrote:
> On 01/21/2013 11:07 AM, Sascha Hauer wrote:
>> On Mon, Jan 21, 2013 at 09:56:24AM +0100, Wolfgang Grandegger wrote:
>>> On 01/21/2013 09:37 AM, Sascha Hauer wrote:
>>>> There may be multiple phys on an mdio bus. This series adds support
>>>> for this to the fec driver. I recently had a board which has a switch
>>>> connected to the fec's mdio bus, so I had to pick the correct phy.
>>>
>>> Pick one PHY from a switch port? Well, does a PHY-less (or fixed-link)
>>> configuration for a switch not make more sense?
>>
>> Yes, you're probably right.
>>
>>> Various ARM Ethernet
>>> contoller drivers do not support it. I recently needed a hack for an
>>> AT91 board.
>>
>> I wonder how we want to proceed. Should there be a devicetree property
>> 'fixed-link' like done for fs_enet (and not recommended for new code,
>> stated in the comment above of_phy_connect_fixed_link)?
>
> Also the gianfar and ucc_geth drivers use this interface (via fixed
> link phy). I tried to use it for the AT91 macb driver but stopped
> quickly because the usage was not straight forward (too much code)...
> even if the idea of using a fake fixed-link phy is not bad.
>
>> Currently I have a property 'phy' in the fec binding which has a phandle
>> to a phy provided by the fec's mdio bus, but this could equally well
>
> But than the cable must be connected to the associated switch port.
>
>> point to a fixed dummy phy:
>>
>> 	phy = &fixed-phy;
>
> The link speed, full/half duplex and maybe some mroe parameter should
> be configurable via device tree.
>
>> Currently there seems to be no common convention for the devicetree how
>> to handle such situations, or am I missing something?
>
> That's also may impression. There seem to be a few more related hacks:
>
> $ find . -name '*.c'| xargs grep -i "phy-less"
> ./ethernet/amd/au1000_eth.c:			netdev_info(dev, "using PHY-less setup\n");
> ./ethernet/amd/au1000_eth.c:	} else { /* PHY-less op, assume full-duplex */
> ./ethernet/ibm/emac/core.c:	/* PHY-less configuration.
> ./ethernet/ibm/emac/core.c:		/* PHY-less configuration.
>
> I would prefer to handle the "fixed-link" property of the ethernet dt
> node directly in the driver with a generic helper function.

Is not what of_phy_connect_fixed_link() offer? I am not sure there can 
be much done by an helper than that.
--
Florian
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