Subject: [PATCH net-next v2 0/5] net: phylink: fix PCS without autoneg

From: "Russell King (Oracle)" <[email-masked]>
Date: Mon, 13 Jan 2025 09:21:18 +0000

Hi,

Eric Woudstra reported that a PCS attached using 2500base-X does not
see link when phylink is using in-band mode, but autoneg is disabled,
despite there being a valid 2500base-X signal being received. We have
these settings:

	act_link_an_mode = MLO_AN_INBAND
	pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED

Eric diagnosed it to phylink_decode_c37_word() setting state->link
false because the full-duplex bit isn't set in the non-existent link
partner advertisement word (which doesn't exist because in-band
autoneg is disabled!)

The test in phylink_mii_c22_pcs_decode_state() is supposed to catch
this state, but since we converted PCS to use neg_mode, testing the
Autoneg in the local advertisement is no longer sufficient - we need
to be looking at the neg_mode, which currently isn't provided.

We need to provide this via the .pcs_get_state() method, and this
will require modifying all PCS implementations to add the extra
argument to this method.

Patch 1 uses the PCS neg_mode in phylink_mac_pcs_get_state() to correct
the now obsolute usage of the Autoneg bit in the advertisement.

Patch 2 passes neg_mode into the .pcs_get_state() method, and updates
all users.

Patch 3 adds neg_mode as an argument to the various clause 22 state
decoder functions in phylink, modifying drivers to pass the neg_mode
through.

Patch 4 makes use of phylink_mii_c22_pcs_decode_state() rather than
using the Autoneg bit in the advertising field.

Patch 5 may be required for Eric's case - it ensures that we report
the correct state for interface types that we support only one set
of modes for when autoneg is disabled.

Changes in v2:
- Add test for NULL pcs in patch 1

I haven't added Eric's t-b because I used a different fix in patch 1.

 drivers/net/dsa/b53/b53_serdes.c                   |  4 +-
 drivers/net/dsa/mt7530.c                           |  2 +-
 drivers/net/dsa/mv88e6xxx/pcs-6185.c               |  1 +
 drivers/net/dsa/mv88e6xxx/pcs-6352.c               |  1 +
 drivers/net/dsa/mv88e6xxx/pcs-639x.c               |  5 +-
 drivers/net/dsa/qca/qca8k-8xxx.c                   |  2 +-
 drivers/net/ethernet/cadence/macb_main.c           |  3 +-
 drivers/net/ethernet/freescale/fman/fman_dtsec.c   |  4 +-
 drivers/net/ethernet/marvell/mvneta.c              |  2 +-
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c    |  2 +
 .../net/ethernet/marvell/prestera/prestera_main.c  |  1 +
 drivers/net/ethernet/meta/fbnic/fbnic_phylink.c    |  2 +-
 .../net/ethernet/microchip/lan966x/lan966x_main.h  |  2 +-
 .../ethernet/microchip/lan966x/lan966x_phylink.c   |  3 +-
 .../net/ethernet/microchip/lan966x/lan966x_port.c  |  4 +-
 .../net/ethernet/microchip/sparx5/sparx5_phylink.c |  2 +-
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c  |  3 +-
 drivers/net/pcs/pcs-lynx.c                         |  4 +-
 drivers/net/pcs/pcs-mtk-lynxi.c                    |  4 +-
 drivers/net/pcs/pcs-xpcs.c                         |  7 +--
 drivers/net/phy/phylink.c                          | 60 ++++++++++++++++------
 include/linux/phylink.h                            | 11 ++--
 22 files changed, 87 insertions(+), 42 deletions(-)

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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