netdev - Re: [PATCH v2] net: sh_eth: do not advertise Gigabit capabilities when not available

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Date:   Tue, 5 Dec 2017 22:02:20 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        "David S. Miller" <davem@...emloft.net>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms+renesas@...ge.net.au>
Cc:     netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] net: sh_eth: do not advertise Gigabit capabilities
 when not available

Hello!

On 12/05/2017 12:29 PM, Thomas Petazzoni wrote:

> Not all variants of the sh_eth hardware have Gigabit
> support. Unfortunately, the current driver doesn't tell the PHY about
> the limited MAC capabilities. Due to this, if you have a Gigabit
> capable PHY, the PHY will advertise its Gigabit capability and
> establish a link at 1Gbit/s, even though the MAC doesn't support it.
> 
> In order to avoid this, we use the recently introduced
> phy_set_max_speed() to tell the PHY to not advertise speed higher than
> 100 MBit/s.
> 
> Tested on a SH7786 platform, with a Gigabit PHY.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
> ---
> Changes since v1:
>   - Use phy_set_max_speed(), as suggested by Sergei Shtylyov
>     <sergei.shtylyov@...entembedded.com>.
> ---
>   drivers/net/ethernet/renesas/sh_eth.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
> index db72d13cebb9..44ff2835c954 100644
> --- a/drivers/net/ethernet/renesas/sh_eth.c
> +++ b/drivers/net/ethernet/renesas/sh_eth.c
[...]
> @@ -1892,9 +1893,22 @@ static int sh_eth_phy_init(struct net_device *ndev)
>   		return PTR_ERR(phydev);
>   	}
>   
> +	/* mask with MAC supported features */
> +	if (mdp->cd->register_type != SH_ETH_REG_GIGABIT) {
> +		err = phy_set_max_speed(phydev, SPEED_100);
> +		if (err) {
> +			netdev_err(ndev, "failed to limit PHY to 100 Mbit/s\n");
> +			goto err_phy_disconnect;

    Er, why do we need a *goto* here at all? Just call phy_disconnect() here 
and be done with that...

> +		}
> +	}
> +
>   	phy_attached_info(phydev);
>   
>   	return 0;
> +
> +err_phy_disconnect:
> +	phy_disconnect(phydev);
> +	return err;
>   }
>   
>   /* PHY control start function */

MBR, Sergei