net: ethtool: add KSZ87xx low-loss cable PHY tunables

Introduce vendor-specific PHY tunable identifiers to control the
KSZ87xx low-loss cable erratum handling through the ethtool PHY
tunable interface.

The following tunables are added:

- a boolean "short-cable" tunable, applying a documented and
  conservative preset intended for short or low-loss Ethernet cables;

- an integer LPF bandwidth tunable, allowing advanced adjustment of the
  receiver low-pass filter bandwidth;

- an integer DSP EQ initial value tunable, allowing advanced tuning of
  the PHY equalizer initialization.

The actual behavior is implemented by the corresponding PHY and switch
drivers.

Reviewed-by: Marek Vasut <marex@nabladev.com>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Signed-off-by: Fidelio Lawson <fidelio.lawson@exotec.com>
Link: https://patch.msgid.link/20260609-ksz87xx_errata_low_loss_connections-v10-2-9ba4418cf3db@exotec.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index 1cdfb8341df2..a2091d4e00f3 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -291,6 +291,9 @@ enum phy_tunable_id {
 	ETHTOOL_PHY_DOWNSHIFT,
 	ETHTOOL_PHY_FAST_LINK_DOWN,
 	ETHTOOL_PHY_EDPD,
+	ETHTOOL_PHY_SHORT_CABLE_PRESET,
+	ETHTOOL_PHY_LPF_BW,
+	ETHTOOL_PHY_DSP_EQ_INIT_VALUE,
 	/*
 	 * Add your fresh new phy tunable attribute above and remember to update
 	 * phy_tunable_strings[] in net/ethtool/common.c