linux-kernel - Re: [PATCH net v2] net: phy: realtek: add support for RTL8366S Gigabit PHY

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Message-ID: <20240726092655.15e66731@fedora.home>
Date: Fri, 26 Jul 2024 09:26:55 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Mark Mentovai <mark@...tovai.com>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit
 <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>, "David S .
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org, Oleksij Rempel <o.rempel@...gutronix.de>,
 Jonas Gorski <jonas.gorski@...il.com>, Russell Senior
 <russell@...sonaltelco.net>, Lóránd Horváth
 <lorand.horvath82@...il.com>, Mieczyslaw Nalewaj <namiltd@...oo.com>, Shiji
 Yang <yangshiji66@...look.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net v2] net: phy: realtek: add support for RTL8366S
 Gigabit PHY

Hello Mark,

On Thu, 25 Jul 2024 16:41:44 -0400
Mark Mentovai <mark@...tovai.com> wrote:

> The PHY built in to the Realtek RTL8366S switch controller was
> previously supported by genphy_driver. This PHY does not implement MMD
> operations. Since commit 9b01c885be36 ("net: phy: c22: migrate to
> genphy_c45_write_eee_adv()"), MMD register reads have been made during
> phy_probe to determine EEE support. For genphy_driver, these reads are
> transformed into 802.3 annex 22D clause 45-over-clause 22
> mmd_phy_indirect operations that perform MII register writes to
> MII_MMD_CTRL and MII_MMD_DATA. This overwrites those two MII registers,
> which on this PHY are reserved and have another function, rendering the
> PHY unusable while so configured.
> 
> Proper support for this PHY is restored by providing a phy_driver that
> declares MMD operations as unsupported by using the helper functions
> provided for that purpose, while remaining otherwise identical to
> genphy_driver.
> 
> Fixes: 9b01c885be36 ("net: phy: c22: migrate to genphy_c45_write_eee_adv()")
> Reported-by: Russell Senior <russell@...sonaltelco.net>
> Closes: https://github.com/openwrt/openwrt/issues/15981
> Link: https://github.com/openwrt/openwrt/issues/15739
> Signed-off-by: Mark Mentovai <mark@...tovai.com>

This looks correct to me.

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

Thanks,

Maxime