linux-kernel - Re: [PATCH net-next v3 15/15] net: fec: add support for PHYs with SmartEEE support

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Date:   Tue, 31 Jan 2023 22:52:31 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Arun.Ramadoss@...rochip.com
Subject: Re: [PATCH net-next v3 15/15] net: fec: add support for PHYs with
 SmartEEE support

On Mon, Jan 30, 2023 at 09:07:14AM +0100, Oleksij Rempel wrote:
> Ethernet controller in i.MX6*/i.MX7* series do not provide EEE support.
> But this chips are used sometimes in combinations with SmartEEE capable
> PHYs.
> So, instead of aborting get/set_eee access on MACs without EEE support,
> ask PHY if it is able to do the EEE job by using SmartEEE.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
>  drivers/net/ethernet/freescale/fec_main.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index e6238e53940d..25a2a9d860de 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -3102,8 +3102,15 @@ fec_enet_get_eee(struct net_device *ndev, struct ethtool_eee *edata)
>  	struct fec_enet_private *fep = netdev_priv(ndev);
>  	struct ethtool_eee *p = &fep->eee;
>  
> -	if (!(fep->quirks & FEC_QUIRK_HAS_EEE))
> -		return -EOPNOTSUPP;
> +	if (!(fep->quirks & FEC_QUIRK_HAS_EEE)) {
> +		if (!netif_running(ndev))
> +			return -ENETDOWN;
> +
> +		if (!phy_has_smarteee(ndev->phydev))
> +			return -EOPNOTSUPP;
> +
> +		return phy_ethtool_get_eee(ndev->phydev, edata);

I see many places in the fec driver guarding against a NULL
ndev->phydev, and TBH I don't completely understand why.
I guess it's because ndev->phydev is populated at fec_enet_open() time.

But then again, if the netif_running() check is sufficient to imply
presence of ndev->phydev as you suggest, then why does fec_enet_ioctl()
have this?

	if (!netif_running(ndev))
		return -EINVAL;

	if (!phydev)
		return -ENODEV;

Asking because phy_init_eee(), phy_ethtool_set_eee() and
phy_ethtool_get_eee() don't support being called with a NULL phydev.