Re: [PATCH net-next v2] net: pcs: lynx: add support for 25GBASE-R

From: Vincent Jardin <vjardin@free.fr>

The Lynx PCS never supported 25GBASE-R. Add it, so that a 25G DPMAC on
LX2160A can be driven by phylink.

The SerDes side had the mode since the commit
 1cab8fba5073 ("phy: lynx-28g: add support for 25GBASER")
and dpaa2-mac maps DPMAC_ETH_IF_CAUI to PHY_INTERFACE_MODE_25GBASER,
but the PCS never handled it, so phylink_validate() failed with the
interface.

25GBASE-R is a serial mode without clause-37 in-band autonegotiation,
exactly like 10GBASE-R: it does not needs any configuration, its state
is read with phylink_mii_c45_pcs_get_state(), and it reports
LINK_INBAND_DISABLE.

phylink_mii_c45_pcs_get_state() is extended in the same patch because
without it the link comes up reporting Unknown/Unknown.

Suggested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Co-developed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Vincent Jardin <vjardin@free.fr>
---
Repost of the RFC now that net-next has reopened, rebased on net-next.
---
Changes in v2:
- Reword: this adds 25GBASE-R support, it does not fix a regression
 (Ioana Ciornei)
- Squash in the phylink_mii_c45_pcs_get_state() 25GBASER case, without
 which the link comes up as Unknown/Unknown (Ioana Ciornei)
- Link to v1: https://lore.kernel.org/r/20260825-for-upstream-lynx-25gbaser-v1-v1-1-fd71c8047798@free.fr (local)
---
drivers/net/pcs/pcs-lynx.c | 6 +++++-
drivers/net/phy/phylink.c  | 5 +++++
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/net/pcs/pcs-lynx.c b/drivers/net/pcs/pcs-lynx.c
index a92081560e641..da4f99059eef7 100644
--- a/drivers/net/pcs/pcs-lynx.c
+++ b/drivers/net/pcs/pcs-lynx.c

@@ -46,6 +46,7 @@ static unsigned int lynx_pcs_inband_caps(struct phylink_pcs *pcs,

		return LINK_INBAND_DISABLE | LINK_INBAND_ENABLE;

	case PHY_INTERFACE_MODE_10GBASER:
+	case PHY_INTERFACE_MODE_25GBASER:
		return LINK_INBAND_DISABLE;

	case PHY_INTERFACE_MODE_USXGMII:

@@ -97,6 +98,7 @@ static void lynx_pcs_get_state(struct phylink_pcs *pcs, unsigned int neg_mode,

		lynx_pcs_get_state_usxgmii(lynx->mdio, state);
		break;
	case PHY_INTERFACE_MODE_10GBASER:
+	case PHY_INTERFACE_MODE_25GBASER:
		phylink_mii_c45_pcs_get_state(lynx->mdio, state);
		break;
	default:

@@ -188,7 +190,8 @@ static int lynx_pcs_config(struct phylink_pcs *pcs, unsigned int neg_mode,

		return lynx_pcs_config_usxgmii(lynx->mdio, ifmode, advertising,
					       neg_mode);
	case PHY_INTERFACE_MODE_10GBASER:
-		/* Nothing to do here for 10GBASER */
+	case PHY_INTERFACE_MODE_25GBASER:
+		/* Nothing to do here for 10GBASER and 25GBASER */
		break;
	default:
		return -EOPNOTSUPP;

@@ -279,6 +282,7 @@ static const phy_interface_t lynx_interfaces[] = {

	PHY_INTERFACE_MODE_1000BASEX,
	PHY_INTERFACE_MODE_2500BASEX,
	PHY_INTERFACE_MODE_10GBASER,
+	PHY_INTERFACE_MODE_25GBASER,
	PHY_INTERFACE_MODE_USXGMII,
	PHY_INTERFACE_MODE_10G_QXGMII,
};

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 3ec3bb4391095..ff4375f1e9108 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c

@@ -4360,6 +4360,11 @@ void phylink_mii_c45_pcs_get_state(struct mdio_device *pcs,

		state->duplex = DUPLEX_FULL;
		break;

+	case PHY_INTERFACE_MODE_25GBASER:
+		state->speed = SPEED_25000;
+		state->duplex = DUPLEX_FULL;
+		break;
+
	default:
		break;
	}

---
base-commit: c8ea08ba34f2a2e9bfb18ff3d69eb2d69b324f49
change-id: 20260825-for-upstream-lynx-25gbaser-v1-30097d909d09

Best regards,