netdev - Re: [PATCH] net: stmmac: get phydev->interface from mac for mdio phy init

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Message-ID: <Y+OkWiGAr1ysMxSt@shell.armlinux.org.uk>
Date:   Wed, 8 Feb 2023 13:32:10 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Guan Wentao <guanwentao@...ontech.com>
Cc:     peppe.cavallaro@...com, alexandre.torgue@...s.st.com,
        joabreu@...opsys.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, mcoquelin.stm32@...il.com,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] net: stmmac: get phydev->interface from mac for mdio phy
 init

[Not fully over covid but I spotted this and don't agree with this change]

On Wed, Feb 08, 2023 at 08:40:25PM +0800, Guan Wentao wrote:
> The phy->interface from mdiobus_get_phy is default from phy_device_create.
> In some phy devices like at803x, use phy->interface to init rgmii delay.
> Use plat->phy_interface to init if know from stmmac_probe_config_dt.
> 
> Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> Signed-off-by: Guan Wentao <guanwentao@...ontech.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 1a5b8dab5e9b..debfcb045c22 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1162,6 +1162,12 @@ static int stmmac_init_phy(struct net_device *dev)
>  			return -ENODEV;
>  		}
>  
> +		/* If we know the interface, it defines which PHY interface */
> +		if (priv->plat->phy_interface > 0) {
> +			phydev->interface = priv->plat->phy_interface;
> +			netdev_dbg(priv->dev, "Override default phy interface\n");
> +		}
> +

Why do you need to do this?

You call phylink_create() with ->phy_interface, which tells phylink
which interface you want to use. Then, phylink_connect_phy().

phylink will then call phylink_attach_phy() and then phy_attach_direct()
with the interface you asked for (which was ->phy_interface).

phy_attach_direct() will then set phydev->interface to that interface
mode.

So, I think what you have above is a hack rather than a proper fix,
and the real problem is elsewhere.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!