Re: assert in phylink.c with lan7801 and dp83tc811 since kernel 6.18

[Andrew Lunn <andrew@lunn.ch>]

> 	phylink_dbg(pl, "phy: --3.4 supported    0x%x\n", supported);

supported is a pointer, so you cannot get anything useful from
printing its value.

> [    2.771616] lan78xx 1-1.4:1.0 (unnamed net_device) (uninitialized): validation of rgmii-id with support 00000000,00000000,00000000,00006280 and advertisement 00000000,00000000,00000000,00006280 failed: -EINVAL
 
> But I do not get what phylink_is_empty_linkmode() is doing...

The supported value is a combination of a few things. It indicates if
the PHY supports auto negotiation, pause, asym pause, if the link is
using twisted pair, fibre etc. It also lists the speeds the PHY
supports. There is a list here:

https://elixir.bootlin.com/linux/v7.0.1/source/include/uapi/linux/ethtool.h#L1963

Decoding 00006280 we get:

ETHTOOL_LINK_MODE_TP_BIT,
ETHTOOL_LINK_MODE_MII_BIT,
ETHTOOL_LINK_MODE_Pause_BIT,
ETHTOOL_LINK_MODE_Asym_Pause_BIT

So Maxime was correct, it is not listing any link speeds. From what i
understand, it is a 100BaseT1? So you would expect to see:

ETHTOOL_LINK_MODE_100baseT1_Full_BIT

which is bit 67.

phylib asks the PHY what it can do. For BaseT1 that would be
genphy_c45_pma_baset1_read_abilities()

https://elixir.bootlin.com/linux/v7.0.1/source/drivers/net/phy/phy-c45.c#L971

either the PHY has the wrong value in its register, or the function is
not getting called.

The PHY is an dp83tc811?

https://elixir.bootlin.com/linux/v7.0.1/source/drivers/net/phy/dp83tc811.c#L387

It does not set .get_features. However, dp83tg720.c does:

https://elixir.bootlin.com/linux/v7.0.1/source/drivers/net/phy/dp83tg720.c#L654

So try adding:

	.get_features	= genphy_c45_pma_read_ext_abilities,

	Andrew