linux-kernel - Re: [PATCHv1 1/6] net: dsa: Support internal phy on 'cpu' port

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Date:   Wed, 3 Jan 2018 14:21:28 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Sebastian Reichel <sebastian.reichel@...labora.co.uk>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Ian Ray <ian.ray@...com>, Nandor Han <nandor.han@...com>,
        Rob Herring <robh+dt@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv1 1/6] net: dsa: Support internal phy on 'cpu' port

On Wed, Jan 03, 2018 at 01:26:04PM +0100, Sebastian Reichel wrote:
> This adds support for enabling the internal phy for a 'cpu' port.
> It has been tested on GE B850v3 and B650v3, which have a built-in
> MV88E6240 switch connected to a PCIe based network card. Without
> this patch the link does not come up and no traffic can be routed
> through the switch.
> 
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.co.uk>
> ---
>  net/dsa/port.c | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/net/dsa/port.c b/net/dsa/port.c
> index bb4be2679904..f99c1d34416c 100644
> --- a/net/dsa/port.c
> +++ b/net/dsa/port.c
> @@ -282,6 +282,10 @@ int dsa_port_fixed_link_register_of(struct dsa_port *dp)
>  	int mode;
>  	int err;
>  
> +	mode = of_get_phy_mode(dn);
> +	if (mode < 0)
> +		mode = PHY_INTERFACE_MODE_NA;
> +
>  	if (of_phy_is_fixed_link(dn)) {
>  		err = of_phy_register_fixed_link(dn);
>  		if (err) {
> @@ -292,10 +296,6 @@ int dsa_port_fixed_link_register_of(struct dsa_port *dp)
>  		}
>  
>  		phydev = of_phy_find_device(dn);
> -
> -		mode = of_get_phy_mode(dn);
> -		if (mode < 0)
> -			mode = PHY_INTERFACE_MODE_NA;
>  		phydev->interface = mode;
>  
>  		genphy_config_init(phydev);
> @@ -305,6 +305,24 @@ int dsa_port_fixed_link_register_of(struct dsa_port *dp)
>  			ds->ops->adjust_link(ds, port, phydev);
>  
>  		put_device(&phydev->mdio.dev);
> +	} else if (mode == PHY_INTERFACE_MODE_INTERNAL ||
> +		   mode == PHY_INTERFACE_MODE_NA) {

Hi Sebastian

I understand what you are trying to do, i've got boards which also
have back-to-back PHYs for the CPU port. These boards however have the
strapping correct, so nothing needs doing in software.

But the way you are doing it is wrong. PHY_INTERFACE_MODE_NA means
something else has already setup the interface mode, leave it alone.
PHY_INTERFACE_MODE_INTERNAL means there is some other sort of bus
between the MAC and the PHY than the normal MII.

What you want to say is that there is a PHY on this port, and that you
want to configure it to a given fixed configuration, probably 1000
Full, with auto-neg turned off. This is something completely different
to a fixed phy, which is used when there is no PHY at all.

What state is the PHY in, if you don't have this patch? Is it powered
down?

	Andrew