netdev - Re: [PATCH v2 net-next 1/7] net: phy: realtek: configure SerDes mode for rtl822x/8251b PHYs

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Message-ID: <26f86865-79e5-422f-9e99-bbc71933c718@gmail.com>
Date: Tue, 5 Mar 2024 09:44:52 +0100
From: Eric Woudstra <ericwouds@...il.com>
To: Daniel Golle <daniel@...rotopia.org>,
 Heiner Kallweit <hkallweit1@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, 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>,
 Marek Behún <kabel@...nel.org>,
 Frank Wunderlich <frank-w@...lic-files.de>, netdev@...r.kernel.org,
 Alexander Couzens <lynxis@...0.eu>
Subject: Re: [PATCH v2 net-next 1/7] net: phy: realtek: configure SerDes mode
 for rtl822x/8251b PHYs

On 3/3/24 22:08, Daniel Golle wrote:

> None of this should be done on RealTek NICs, and the easiest way to
> prevent that is to test if phydev->phylink is NULL or not (as the NIC
> driver doesn't use phylink but rather just calls phy_connect_direct()).
> 
> Also note that the datasheet with the magic SerDes config sequences
> lists only 2nd generation 2.5G PHYs as supported:
> RTL8226B
> RTL8221B(I)
> RTL8221B(I)-VB
> RTL8221B(I)-VM
> 
> So RTL8226 and RTL8226-CG are **not** listed there and being from the
> 1st generation of RealTek 2.5G PHYs I would assume that it won't
> support setting up the SerDes mode in this way.
> 
> Afaik those anyway were only used in early RealTek-based 2.5G switches
> and maybe NICs, I'm pretty sure you won't find them inside SFP modules
> or as part non-RealTek-based routers or switches -- hence switching
> SerDes mode most likely anyway will never be required for those.

Then it would be best to change all patches in this patch-set to only
modify the driver instances of:

"RTL8226B_RTL8221B 2.5Gbps PHY"
"RTL8226B-CG_RTL8221B-CG 2.5Gbps PHY"
"RTL8221B-VB-CG 2.5Gbps PHY"
"RTL8221B-VM-CG 2.5Gbps PHY"

And NOT to modify:

"RTL8226 2.5Gbps PHY
"RTL8226-CG 2.5Gbps PHY"
"RTL8251B 5Gbps PHY"

Or are there more restrictions? If so, why is it a restriction?
Perhaps this can help me find an expression to use as match.

Best regards,

Eric Woudstra