Re: [PATCH net] net: usb: lan78xx: resume phylink on non-reset USB resume

[Oleksij Rempel]

Hi Stefano,

On Tue, Nov 03, 2026 at 12:51:33AM +0100, Stefano Munari wrote:
> lan78xx_suspend() calls phylink_suspend(dev->phylink, false) on an open
> interface, which always stops phylink and halts the PHY. The matching
> phylink_resume() is only called from lan78xx_reset_resume().
> When the USB device stays powered across system sleep (e.g. s2idle) and
> the USB core calls .resume instead, the link stays down until the interface
> is brought down and up by hand. The ifdown triggers:
> 
>   WARNING: drivers/net/phy/phy.c:1670 at phy_stop+0x44/0xc8
>   called from state HALTED
> 
> Move phylink_resume() to the end of lan78xx_resume(), which both resume
> paths go through, and call it only if the resume succeeded and the
> interface was open, mirroring lan78xx_suspend(). As a side effect,
> lan78xx_reset_resume() no longer starts phylink on a closed interface.
> 
> Tested on a Raspberry Pi 3B+ (LAN7515) with s2idle: the link now comes
> back up on its own after resume and ifdown no longer warns.
> 
> Fixes: e110bc825897 ("net: usb: lan78xx: Convert to PHYLINK for improved PHY and MAC management")
> Signed-off-by: Stefano Munari <stefanomunari.sm@xxxxxxxxx>

Partially tested on net-next (4dd16e31135e) with a LAN7850 on an
i.MX8MP. The USB host is reinitialized across s2idle here, so only
.reset_resume is used. With the interface closed, s2idle resume no
longer shows "multicast write failed -EACCES" and the WARNING at
phy.c:1352 in _phy_state_machine() (4/4 without, 0/4 with this patch).
An open interface still comes back after resume. The plain .resume
path, which is the main case of this patch, is not tested.

Tested-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>

Thank you!

Best Regards,
Oleksij
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