netdev - Re: [PATCH net-next v3 1/3] net: dp83869: Add ability to advertise Fiber connection

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Message-ID: <20200905111755.4bd874b2@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 5 Sep 2020 11:17:55 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Dan Murphy <dmurphy@...com>
Cc:     <davem@...emloft.net>, <andrew@...n.ch>, <f.fainelli@...il.com>,
        <hkallweit1@...il.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 1/3] net: dp83869: Add ability to advertise
 Fiber connection

On Thu, 3 Sep 2020 06:42:57 -0500 Dan Murphy wrote:
> Add the ability to advertise the Fiber connection if the strap or the
> op-mode is configured for 100Base-FX.
> 
> Auto negotiation is not supported on this PHY when in fiber mode.
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>

Some comments, I'm not very phy-knowledgeable so bear with me
(hopefully PHY maintainers can correct me, too).

> diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
> index 58103152c601..48a68474f89c 100644
> --- a/drivers/net/phy/dp83869.c
> +++ b/drivers/net/phy/dp83869.c
> @@ -52,6 +52,11 @@
>  					 BMCR_FULLDPLX | \
>  					 BMCR_SPEED1000)
>  
> +#define MII_DP83869_FIBER_ADVERTISE    (ADVERTISED_TP | ADVERTISED_MII | \
> +					ADVERTISED_FIBRE | ADVERTISED_BNC |  \

I'm not actually sure myself what the semantics of port type advertise
bits are, but if this is fiber why advertise TP and do you really have
BNC connectors? :S

> +					ADVERTISED_Pause | ADVERTISED_Asym_Pause | \
> +					ADVERTISED_100baseT_Full)

You say 100Base-FX, yet you advertise 100Base-T?

>  /* This is the same bit mask as the BMCR so re-use the BMCR default */
>  #define DP83869_FX_CTRL_DEFAULT	MII_DP83869_BMCR_DEFAULT
>  
> @@ -300,6 +305,7 @@ static int dp83869_configure_mode(struct phy_device *phydev,
>  {
>  	int phy_ctrl_val;
>  	int ret;
> +	int bmcr;

Please keep reverse xmas tree ordering.

>  	if (dp83869->mode < DP83869_RGMII_COPPER_ETHERNET ||
>  	    dp83869->mode > DP83869_SGMII_COPPER_ETHERNET)
> @@ -383,7 +389,37 @@ static int dp83869_configure_mode(struct phy_device *phydev,
>  
>  		break;
>  	case DP83869_RGMII_1000_BASE:
> +		break;
>  	case DP83869_RGMII_100_BASE:
> +		/* Only allow advertising what this PHY supports */
> +		linkmode_and(phydev->advertising, phydev->advertising,
> +			     phydev->supported);
> +
> +		linkmode_set_bit(ETHTOOL_LINK_MODE_FIBRE_BIT,
> +				 phydev->supported);
> +		linkmode_set_bit(ETHTOOL_LINK_MODE_FIBRE_BIT,
> +				 phydev->advertising);
> +
> +		/* Auto neg is not supported in fiber mode */
> +		bmcr = phy_read(phydev, MII_BMCR);
> +		if (bmcr < 0)
> +			return bmcr;
> +
> +		phydev->autoneg = AUTONEG_DISABLE;
> +		linkmode_clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
> +				   phydev->supported);
> +		linkmode_clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
> +				   phydev->advertising);
> +
> +		if (bmcr & BMCR_ANENABLE) {
> +			ret =  phy_modify(phydev, MII_BMCR, BMCR_ANENABLE, 0);
> +			if (ret < 0)
> +				return ret;
> +		}
> +
> +		phy_modify_changed(phydev, MII_ADVERTISE,
> +				   MII_DP83869_FIBER_ADVERTISE,
> +				   MII_DP83869_FIBER_ADVERTISE);

This only accesses standard registers, should it perhaps be a helper in
the kernel's phy code?

>  		break;
>  	default:
>  		return -EINVAL;