AW: pre-boot plugged SFP autoneg advertisement

[<markus.stockhausen@gmx.de>]

Hi Andrew,

> Von: Andrew Lunn <andrew@lunn.ch> 
> Betreff: Re: pre-boot plugged SFP autoneg advertisement
> 
> > On Sat, Apr 18, 2026 at 11:27:40AM +0200, markus.stockhausen@gmx.de
wrote:
> > Hi,
> > 
> > I'm currently analyzing an issue where a pre-boot-plugged SFP module 
> > comes up with autoneg=no advertisement during boot. After an
> > unplug/replug autoneg=yes advertisement is chosen. 
> > 
> > The following addition in phylink_start() just before the call to
> > phylink_mac_initial_config() mitigiates this.
> > 
> > +  /* If an SFP module was already present before phylink_start() was
> > +   * called, phylink_sfp_set_config() was unable to call
> > +   * phylink_mac_initial_config() as phylink was not yet started.
> > +   * Ensure the SFP capabilities are reflected in advertising.
> > +   */
> > +  if (pl->sfp_bus && !linkmode_empty(pl->sfp_support))
> > +    linkmode_copy(pl->link_config.advertising, pl->sfp_support);
>
> Let me see if i have the call chain correct. This is net-next/main
> from today.
>
> phylink_sfp_connect_phy() ->
>   phylink_sfp_config_phy
>
>         if (changed && !test_bit(PHYLINK_DISABLE_STOPPED,
>                                  &pl->phylink_disable_state))
>                 phylink_mac_initial_config(pl, false);
>
> You are saying PHYLINK_DISABLE_STOPPED is set, so
> phylink_mac_initial_config() is not called.
>
> What i don't see is how phylink_mac_initial_config() does the
> linkmode_copy() you are adding.

Took that hint/question and digged deeper. Added further debug
to each and every linkmode_copy. I think I found the culprit in 
a userspace ethtool call. For now I assume OpenWrt netifd.
Adding my last trace below including the original (wrong) idea. 

Thank you very much for taking the time and your assistance.

Markus

[    3.301299] XXXX phylink_create lan12 set pl->link_config.advertising
(autoneg = 1)
[    3.309954] XXXX phylink_parse_mode lan12 set pl->link_config.advertising
(autoneg = 1)
[    3.318964] XXX sfp_module_insert lan12 called
[    3.323935] XXXX phylink_sfp_config_optical lan12 set config.advertising
(autoneg = 1)
[    3.332815] XXXX phylink_validate_one lan12 set tmp_supported (autoneg =
1)
[    3.340629] XXXX phylink_validate_mask lan12 set supported (autoneg = 1)
[    3.348165] XXXX phylink_validate_mask lan12 set state->advertising
(autoneg = 1)
[    3.356527] rtl83xx-switch 1b000000.switchcore:ethernet-switch lan12
(uninitialized): XXX phylink_sfp_set_config requesting link mode
inband/1000base-x with support 0000000,00000000,00000200,00006440
--- ETHTOOL CALL HERE ---
[   81.213726] XXXX phylink_ethtool_ksettings_set lan12 start got
config.advertising (autoneg = 1)
[   81.223542] XXXX phylink_ethtool_ksettings_set lan12 set accoring to
kset->base.autoneg (autoneg = 0)
[   81.233961] CPU: 0 UID: 0 PID: 1470 Comm: netifd Tainted: G           O
6.18.21 #0 NONE
[   81.234010] Tainted: [O]=OOT_MODULE
[   81.234017] Hardware name: Zyxel XGS1210-12 A1 Switch
[   81.234026] Stack : 823a3bbc 80139d20 00000000 00000001 00000000 00000000
00000000 00000000
[   81.234094]         00000000 00000000 00000000 00000000 00000000 00000001
823a3b78 82040d00
[   81.234152]         00000000 00000000 80992870 823a3a10 00000000 ffffefff
00000001 00000224
[   81.234213]         00000226 823a39d4 00000226 000019c8 00000001 00000000
80992870 80a00000
[   81.234273]         82764648 00000016 00000016 82764628 00000000 80a913b0
00000000 81990000
[   81.234334]         ...
[   81.234350] Call Trace:
[   81.234356] [<80115e48>] show_stack+0x28/0xf0
[   81.234407] [<8010fc78>] dump_stack_lvl+0x70/0xb0
[   81.234432] [<80592718>] phylink_ethtool_ksettings_set+0x58c/0x6a4
[   81.234479] [<806bb890>] ethtool_set_link_ksettings+0xbc/0x198
[   81.234516] [<806be01c>] __dev_ethtool+0xfe0/0x1a1c
[   81.234550] [<806beb24>] dev_ethtool+0xcc/0x24c
[   81.234575] [<80678770>] dev_ioctl+0x30c/0x5f4
[   81.234616] [<80603ebc>] sock_ioctl+0x2bc/0x470
[   81.234642] [<8036e530>] sys_ioctl+0xb4/0x120
[   81.234683] [<8011edec>] syscall_common+0x34/0x58
[   81.234715]
[   81.234723] XXXX 2 phylink_ethtool_ksettings_set lan12 set
pl->link_config.advertising (autoneg = 0)
-----------
[   81.375070] rtl83xx-switch 1b000000.switchcore:ethernet-switch lan12: XXX
phylink_start configuring for inband/1000base-x link mode
--- INITIAL FIX/IDEA HERE ---
[   81.388408] XXX phylink_start lan12 sfp_bus set and linkmode not empty ->
would run linkmode_copy()
-----------
[   81.398688] XXX phylink_mac_initial_config lan12 called with
force_restart = 1
[   81.406752] rtl83xx-switch 1b000000.switchcore:ethernet-switch lan12: XXX
major config, requested inband/1000base-x
[   81.418459] XXXX major_config_entry lan12: autoneg_adv=0 autoneg_sfp=1
sfp_may_have_phy=0
[   81.427612] XXXX phylink_pcs_neg_mode ENTRY lan12: pl->pcs_neg_mode=0x0
[   81.435102] XXXX phylink_pcs_neg_mode lan12 advertising autoneg=0
[   81.442034] rtl83xx-switch 1b000000.switchcore:ethernet-switch lan12: XXX
interface 1000base-x inband modes: pcs=03 phy=00
[   81.454495] XXXX phylink_pcs_neg_mode lan12 base-x without phy
[   81.461134] XXXX phylink_pcs_neg_mode EXIT lan12 pl->pcs_neg_mode = 0x40
pl->act_link_an_mode = 0x2
[   82.085493] XXXX phylink_mac_pcs_get_state lan12 set state->advertising
(autoneg = 0)
[   82.094391] XXXX phylink_mac_pcs_get_state lan12 autoneg is 0