linux-kernel - Re: [PATCH net-next v3 2/2] net: phy: micrel: Fix forced link mode for KSZ886X switches

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Message-ID: <20231019163212.yzt6erzptuifs5yn@skbuf>
Date:   Thu, 19 Oct 2023 19:32:12 +0300
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>,
        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>,
        Heiner Kallweit <hkallweit1@...il.com>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        netdev@...r.kernel.org,
        Alexander Stein <alexander.stein@...tq-group.com>
Subject: Re: [PATCH net-next v3 2/2] net: phy: micrel: Fix forced link mode
 for KSZ886X switches

On Thu, Oct 19, 2023 at 01:14:59PM +0200, Oleksij Rempel wrote:
> Address a link speed detection issue in KSZ886X PHY driver when in
> forced link mode. Previously, link partners like "ASIX AX88772B"
> with KSZ8873 could fall back to 10Mbit instead of configured 100Mbit.
> 
> The issue arises as KSZ886X PHY continues sending Fast Link Pulses (FLPs)
> even with autonegotiation off, misleading link partners in autoneg mode,
> leading to incorrect link speed detection.
> 
> Now, when autonegotiation is disabled, the driver sets the link state
> forcefully using KSZ886X_CTRL_FORCE_LINK bit. This action, beyond just
> disabling autonegotiation, makes the PHY state more reliably detected by
> link partners using parallel detection, thus fixing the link speed
> misconfiguration.
> 
> With autonegotiation enabled, link state is not forced, allowing proper
> autonegotiation process participation.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>