netdev - Re: [PATCH net v2 1/3] net: phy: smsc: Fix Auto-MDIX configuration when disabled by strap

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Message-ID: <20250704095356.680bd24b@fedora.home>
Date: Fri, 4 Jul 2025 09:53:56 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Andre Edich <andre.edich@...rochip.com>,
 kernel@...gutronix.de, linux-kernel@...r.kernel.org, Russell King
 <linux@...linux.org.uk>, netdev@...r.kernel.org, Lukas Wunner
 <lukas@...ner.de>
Subject: Re: [PATCH net v2 1/3] net: phy: smsc: Fix Auto-MDIX configuration
 when disabled by strap

Hi Oleksij,

On Thu,  3 Jul 2025 13:49:39 +0200
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> Correct the Auto-MDIX configuration to ensure userspace settings are
> respected when the feature is disabled by the AUTOMDIX_EN hardware strap.
> 
> The LAN9500 PHY allows its default MDI-X mode to be configured via a
> hardware strap. If this strap sets the default to "MDI-X off", the
> driver was previously unable to enable Auto-MDIX from userspace.
> 
> When handling the ETH_TP_MDI_AUTO case, the driver would set the
> SPECIAL_CTRL_STS_AMDIX_ENABLE_ bit but neglected to set the required
> SPECIAL_CTRL_STS_OVRRD_AMDIX_ bit. Without the override flag, the PHY
> falls back to its hardware strap default, ignoring the software request.
> 
> This patch corrects the behavior by also setting the override bit when
> enabling Auto-MDIX. This ensures that the userspace configuration takes
> precedence over the hardware strap, allowing Auto-MDIX to be enabled
> correctly in all scenarios.
> 
> Fixes: 05b35e7eb9a1 ("smsc95xx: add phylib support")
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> Cc: Andre Edich <andre.edich@...rochip.com>

Reviewed-by: Maxime Chevallier <maxime.chevallier@...tlin.com>

Maxime