linux-kernel - Re: [net v4] net: phy: Provide Module 4 KSZ9477 errata (DS80000754C)

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Message-ID: <20230905222945.h7tuzlraxdp5imbh@skbuf>
Date:   Wed, 6 Sep 2023 01:29:45 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Lukasz Majewski <lukma@...x.de>
Cc:     Tristram.Ha@...rochip.com, Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew@...n.ch>, davem@...emloft.net,
        Woojung Huh <woojung.huh@...rochip.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, UNGLinuxDriver@...rochip.com,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Michael Walle <michael@...le.cc>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net v4] net: phy: Provide Module 4 KSZ9477 errata (DS80000754C)

On Tue, Sep 05, 2023 at 11:33:15AM +0200, Lukasz Majewski wrote:
> @@ -1847,6 +1844,12 @@ static int ksz9477_config_init(struct phy_device *phydev)
>  			return err;
>  	}
>  
> +	/* According to KSZ9477 Errata DS80000754C (Module 4) all EEE modes
> +	 * in this switch shall be regarded as broken.
> +	 */
> +	if (phydev->dev_flags & MICREL_NO_EEE)
> +		phydev->eee_broken_modes = -1;

I know this is just another quick'n'dirty code snippet exchanged over
email which turned into a proper patch, but wouldn't it be more
civilized to use "MDIO_EEE_100TX | MDIO_EEE_1000T" here, than to declare
EEE broken for link modes which aren't even supported by the internal
switch PHYs?

It's probably not causing practical harm, but currently, we tell
genphy_config_eee_advert() to include reserved bits of the MMD EEE
Advertising Register (MMD 0x07 : 0x3C) into its modification mask.