linux-kernel - Re: [PATCH] net: phy: phy_ethtool_ksettings

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Message-ID: <c1296735-81be-4f7d-a601-bc1a3718a6a2@cogentembedded.com>
Date: Mon, 2 Dec 2024 16:09:43 +0500
From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>,
 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>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Michael Dege <michael.dege@...esas.com>,
 Christian Mardmoeller <christian.mardmoeller@...esas.com>,
 Dennis Ostermann <dennis.ostermann@...esas.com>
Subject: Re: [PATCH] net: phy: phy_ethtool_ksettings_set: Allow any supported
 speed

>> Right now, 'ethtool -s tsn0 master-slave forced-slave' causes a call to
>> driver's ethtool set_link_ksettings method. Which does error out for me
>> because at the call time, speed field is 2500.
> 
> Are you saying that the PHY starts in fixed-speed 2.5G mode?
> 
> What does ethtool tsn0 say after boot and the link has come up but
> before any ethtool settings are changed?

On a freshly booted board, with /etc/systemd/network temporary moved away.

(there are two identical boards, connected to each other)

root@...-033:~# ip l show dev tsn0
19: tsn0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
     link/ether 3a:e3:5c:56:ba:bd brd ff:ff:ff:ff:ff:ff

root@...-033:~# ethtool tsn0
Settings for tsn0:
         Supported ports: [ MII ]
         Supported link modes:   2500baseT/Full
         Supported pause frame use: Symmetric Receive-only
         Supports auto-negotiation: No
         Supported FEC modes: Not reported
         Advertised link modes:  2500baseT/Full
         Advertised pause frame use: No
         Advertised auto-negotiation: No
         Advertised FEC modes: Not reported
         Speed: 2500Mb/s
         Duplex: Unknown! (255)
         Auto-negotiation: off
         master-slave cfg: unknown
         Port: Twisted Pair
         PHYAD: 0
         Transceiver: external
         MDI-X: Unknown

PHY driver is out of tree and can do things wrong. AFAIU it does nothing more than wrapping Marvell 
setup sequences into a phy driver skeleton.

Still, with the patch in question applied, things just work:

root@...-033:~# ip l set dev tsn0 up
root@...-033:~# ethtool -s tsn0 master-slave forced-slave
[   83.743711] renesas_eth_sw e68c0000.ethernet tsn0: Link is Up - 2.5Gbps/Full - flow control off
root@...-033:~# ethtool tsn0
Settings for tsn0:
         Supported ports: [ MII ]
         Supported link modes:   2500baseT/Full
         Supported pause frame use: Symmetric Receive-only
         Supports auto-negotiation: No
         Supported FEC modes: Not reported
         Advertised link modes:  2500baseT/Full
         Advertised pause frame use: No
         Advertised auto-negotiation: No
         Advertised FEC modes: Not reported
         Speed: 2500Mb/s
         Duplex: Full
         Auto-negotiation: off
         master-slave cfg: forced slave
         master-slave status: slave
         Port: Twisted Pair
         PHYAD: 0
         Transceiver: external
         MDI-X: Unknown

root@...-033:~# ip a add 192.168.70.11/24 dev tsn0
root@...-033:~# ping 192.168.70.10
PING 192.168.70.10 (192.168.70.10) 56(84) bytes of data.
64 bytes from 192.168.70.10: icmp_seq=1 ttl=64 time=1.03 ms
64 bytes from 192.168.70.10: icmp_seq=2 ttl=64 time=0.601 ms
...