Subject: Re: [RFC] net: allow FEC driver to not have attached PHY

From: Florian Fainelli <[email-masked]>
Date: Thu, 7 Oct 2010 15:24:43 +0200

Hi,

On Thursday 07 October 2010 05:50:16 Greg Ungerer wrote:
> Hi All,
> 
> I have a board with a ColdFire SoC on it with the built-in FEC
> ethernet module. On this hardware the FEC eth output is directly
> attached to a RTL8305 4-port 10/100 switch. There is no conventional
> PHY, the FEC output is direct into the uplink port of the switch
> chip.
> 
> This setup doesn't work after the FEC code was switch to using
> phylib. The driver used to have code to bypass phy detection/setup
> for this particular board. The phylib probe finds nothing, and of
> course sets a no-link condition.
> 
> So, what is the cleanest way to support this?

If phy detection fails and you cannot attach to a known PHY driver, you could 
register a fixed-PHY driver wich will report the link to be up. I had to do 
something like this for the cpmac driver[1] where various switches and 
external PHY configurations are supported.

[1]: 
https://dev.openwrt.org/browser/trunk/target/linux/ar7/patches-2.6.35/972-
cpmac_multi_probe.patch

> 
> The attached patch adds a config option to do this sort of generically
> for the FEC driver. But I am wondering if there isn't a better way?
> 
> Regards
> Greg
> 
> 
> ---
> 
> [RFC] net: allow FEC driver to not have attached PHY
> 
> At least one board using the FEC driver does not have a conventional
> PHY attached to it, it is directly connected to a somewhat simple
> ethernet switch (the board is the SnapGear/LITE, and the attached
> 4-port ethernet switch is a RealTek RTL8305). This switch does not
> present the usual register interface of a PHY, it presents nothing.
> So a PHY scan will find nothing.
> 
> After the FEC driver was changed to use phylib for supporting phys
> it no longer works on this particular board/switch setup.
> 
> Add a config option to allow configuring the FEC driver to not expect
> a PHY to be present.
> 
> Signed-off-by: Greg Ungerer <[email-masked]>
> ---
>  drivers/net/Kconfig |    9 +++++++++
>  drivers/net/fec.c   |    7 +++++++
>  2 files changed, 16 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index 93494e2..ee44728 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -1934,6 +1934,15 @@ config FEC2
>  	  Say Y here if you want to use the second built-in 10/100 Fast
>  	  ethernet controller on some Motorola ColdFire processors.
> 
> +config FEC_NOPHY
> +	bool "FEC has no attached PHY"
> +	depends on FEC
> +	help
> +	  Some boards using the FEC driver may not have a PHY directly
> +	  attached to it. Typically in this scenario the FEC output is
> +	  directly connected to the input of an ethernet switch or hub.
> +	  Say Y here if your hardware is like this.
> +
>  config FEC_MPC52xx
>  	tristate "MPC52xx FEC driver"
>  	depends on PPC_MPC52xx && PPC_BESTCOMM
> diff --git a/drivers/net/fec.c b/drivers/net/fec.c
> index 768b840..3637f89 100644
> --- a/drivers/net/fec.c
> +++ b/drivers/net/fec.c
> @@ -910,6 +910,11 @@ fec_enet_open(struct net_device *dev)
>  	if (ret)
>  		return ret;
> 
> +#ifdef CONFIG_FEC_NOPHY
> +	/* No PHY connected, assume link is always up */
> +	fep->link = 1;
> +	fec_restart(dev, 0);
> +#else
>  	/* Probe and connect to PHY when open the interface */
>  	ret = fec_enet_mii_probe(dev);
>  	if (ret) {
> @@ -917,6 +922,8 @@ fec_enet_open(struct net_device *dev)
>  		return ret;
>  	}
>  	phy_start(fep->phy_dev);
> +#endif
> +
>  	netif_start_queue(dev);
>  	fep->opened = 1;
>  	return 0;
> --
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