linux-kernel - Re: [PATCH 2/8] net: ethernet: ti: am65-cpsw: Add support for SERDES configuration

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Date:   Wed, 14 Sep 2022 16:37:48 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Siddharth Vadapalli <s-vadapalli@...com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski@...aro.org, krzysztof.kozlowski+dt@...aro.org,
        vladimir.oltean@....com, grygorii.strashko@...com, vigneshr@...com,
        nsekhar@...com, netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kishon@...com
Subject: Re: [PATCH 2/8] net: ethernet: ti: am65-cpsw: Add support for SERDES
 configuration

On Wed, Sep 14, 2022 at 03:20:47PM +0530, Siddharth Vadapalli wrote:
> @@ -1427,6 +1471,9 @@ static void am65_cpsw_nuss_mac_link_down(struct phylink_config *config, unsigned
>  	struct net_device *ndev = port->ndev;
>  	int tmo;
>  
> +	/* disable phy */
> +	am65_cpsw_disable_phy(port->slave.ifphy);
> +

This seems really strange. If you have a serdes interface which
presumably supports SGMII, 1000base-X etc, then link status is sent
across the serdes interface. If you power down the serdes, then you
can't receive the link status, and so mac_link_up() won't be called.

Are you really sure you want to be enabling and disabling the PHY
in mac_link_down()/mac_link_up() ?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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