netdev - Re: [PATCH v3 net-next 07/12] net: ethernet: Add helper to remove a supported link mode

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Date:   Mon, 17 Sep 2018 17:13:07 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v3 net-next 07/12] net: ethernet: Add helper to remove a
 supported link mode

On Wed, Sep 12, 2018 at 01:53:14AM +0200, Andrew Lunn wrote:
> Some MAC hardware cannot support a subset of link modes. e.g. often
> 1Gbps Full duplex is supported, but Half duplex is not. Add a helper
> to remove such a link mode.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/net/ethernet/apm/xgene/xgene_enet_hw.c |  6 +++---
>  drivers/net/ethernet/cadence/macb_main.c       |  5 ++---
>  drivers/net/ethernet/freescale/fec_main.c      |  3 ++-
>  drivers/net/ethernet/microchip/lan743x_main.c  |  2 +-
>  drivers/net/ethernet/renesas/ravb_main.c       |  3 ++-
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c  | 12 ++++++++----
>  drivers/net/phy/phy_device.c                   | 18 ++++++++++++++++++
>  drivers/net/usb/lan78xx.c                      |  2 +-
>  include/linux/phy.h                            |  1 +
>  9 files changed, 38 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c b/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c
> index 078a04dc1182..4831f9de5945 100644

...

> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index aff5516b781e..fb2a1125780d 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1074,7 +1074,8 @@ static int ravb_phy_init(struct net_device *ndev)
>  	}
>  
>  	/* 10BASE is not supported */
> -	phydev->supported &= ~PHY_10BT_FEATURES;
> +	phy_remove_link_mode(phydev, ETHTOOL_LINK_MODE_10baseT_Half_BIT);
> +	phy_remove_link_mode(phydev, ETHTOOL_LINK_MODE_10baseT_Full_BIT);
>  
>  	phy_attached_info(phydev);
>  

...

> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index db1172db1e7c..e9ca83a438b0 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -1765,6 +1765,24 @@ int phy_set_max_speed(struct phy_device *phydev, u32 max_speed)
>  }
>  EXPORT_SYMBOL(phy_set_max_speed);
>  
> +/**
> + * phy_remove_link_mode - Remove a supported link mode
> + * @phydev: phy_device structure to remove link mode from
> + * @link_mode: Link mode to be removed
> + *
> + * Description: Some MACs don't support all link modes which the PHY
> + * does.  e.g. a 1G MAC often does not support 1000Half. Add a helper
> + * to remove a link mode.
> + */
> +void phy_remove_link_mode(struct phy_device *phydev, u32 link_mode)
> +{
> +	WARN_ON(link_mode > 31);
> +
> +	phydev->supported &= ~BIT(link_mode);
> +	phydev->advertising = phydev->supported;
> +}
> +EXPORT_SYMBOL(phy_remove_link_mode);
> +
>  static void of_set_phy_supported(struct phy_device *phydev)
>  {
>  	struct device_node *node = phydev->mdio.dev.of_node;

Hi Andrew,

I believe that for the RAVB the overall effect of this change is that
10-BaseT modes are no longer advertised (although both with and without
this patch they are not supported).

Unfortunately on R-Car Gen3 M3-W (r8a7796) based Salvator-X board
I have observed that this results in the link no longer being negotiated
on one switch (the one I usually use) while it seemed fine on another.