linux-kernel - Re: [PATCH 2/2] net: phy: Provide Module 4 KSZ9477 errata (DS80000754C)

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Message-ID: <20230830112032.GI31399@pengutronix.de>
Date:   Wed, 30 Aug 2023 13:20:32 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Lukasz Majewski <lukma@...x.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew@...n.ch>, davem@...emloft.net,
        Woojung Huh <woojung.huh@...rochip.com>,
        Vladimir Oltean <olteanv@...il.com>, Tristram.Ha@...rochip.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, UNGLinuxDriver@...rochip.com,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: phy: Provide Module 4 KSZ9477 errata
 (DS80000754C)

On Wed, Aug 30, 2023 at 12:08:17PM +0100, Russell King (Oracle) wrote:
> On Wed, Aug 30, 2023 at 11:21:19AM +0200, Lukasz Majewski wrote:
> > +	/* KSZ9477 Errata DS80000754C
> > +	 *
> > +	 * Module 4: Energy Efficient Ethernet (EEE) feature select must be
> > +	 * manually disabled
> > +	 *   The EEE feature is enabled by default, but it is not fully
> > +	 *   operational. It must be manually disabled through register
> > +	 *   controls. If not disabled, the PHY ports can auto-negotiate
> > +	 *   to enable EEE, and this feature can cause link drops when linked
> > +	 *   to another device supporting EEE.
> > +	 *
> > +	 *   Although, the KSZ9477 MMD register
> > +	 *   (MMD_DEVICE_ID_EEE_ADV.MMD_EEE_ADV) advertise that EEE is
> > +	 *   operational one needs to manualy clear them to follow the chip
> > +	 *   errata.
> > +	 */
> > +	linkmode_and(phydev->supported_eee, phydev->supported, zero);
> 
> Hi,
> 
> I'm wondering whether you had a reason to write the above, rather than
> use the simpler:
> 
> 	linkmode_zero(phydev->supported_eee);

Ah, I wondered what was the proper name for this and was not able to
found it.

Thank you!

Regards,
Oleksij
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