[PATCH net-next] net: phylink: add phylink_pcs_loopback() method for PCS loopback support
From: Zxyan Zhu <hidden>
Date: 2026-07-24 08:52:47
Also in:
linux-arm-kernel, lkml
Subsystem:
ethernet phy library, networking drivers, sff/sfp/sfp+ module support, stmmac ethernet driver, the rest · Maintainers:
Andrew Lunn, Heiner Kallweit, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Russell King, Maxime Chevallier, Linus Torvalds
Add a pcs_loopback callback to struct phylink_pcs_ops to allow PCS devices to expose loopback capability. This is useful for MAC drivers running selftests on interfaces that use in-band signalling and have no external PHY device. The phylink_pcs_loopback() helper calls the PCS ops callback if available, and returns -EOPNOTSUPP for PCS devices that do not support loopback. In stmmac, use phylink_pcs_loopback() in stmmac_test_phy_loopback() and stmmac_selftest_run() when no phydev is present but a PCS with loopback support exists. This enables PHY loopback selftests on interfaces without an external PHY. Signed-off-by: Zxyan Zhu <redacted> --- .../stmicro/stmmac/stmmac_selftests.c | 36 ++++++++++++++----- drivers/net/phy/phylink.c | 19 ++++++++++ include/linux/phylink.h | 16 +++++++++ 3 files changed, 63 insertions(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
index 29e824bd90ca..e6ac51018a65 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c@@ -377,20 +377,36 @@ static int stmmac_test_mac_loopback(struct stmmac_priv *priv) static int stmmac_test_phy_loopback(struct stmmac_priv *priv) { struct stmmac_packet_attrs attr = { }; + struct phylink_pcs *pcs; int ret; - if (!priv->dev->phydev) - return -EOPNOTSUPP; + if (priv->dev->phydev) { + ret = phy_loopback(priv->dev->phydev, true, 0); + if (ret) + return ret; - ret = phy_loopback(priv->dev->phydev, true, 0); - if (ret) + attr.dst = priv->dev->dev_addr; + ret = __stmmac_test_loopback(priv, &attr); + + phy_loopback(priv->dev->phydev, false, 0); return ret; + } - attr.dst = priv->dev->dev_addr; - ret = __stmmac_test_loopback(priv, &attr); + /* Use PCS loopback for interfaces without an external PHY. */ + pcs = priv->hw->phylink_pcs; + if (pcs) { + ret = phylink_pcs_loopback(pcs, true); + if (ret) + return ret; - phy_loopback(priv->dev->phydev, false, 0); - return ret; + attr.dst = priv->dev->dev_addr; + ret = __stmmac_test_loopback(priv, &attr); + + phylink_pcs_loopback(pcs, false); + return ret; + } + + return -EOPNOTSUPP; } static int stmmac_test_mmc(struct stmmac_priv *priv)
@@ -1986,6 +2002,8 @@ void stmmac_selftest_run(struct net_device *dev, ret = -EOPNOTSUPP; if (dev->phydev) ret = phy_loopback(dev->phydev, true, 0); + else if (priv->hw->phylink_pcs) + ret = phylink_pcs_loopback(priv->hw->phylink_pcs, true); if (!ret) break; fallthrough;
@@ -2019,6 +2037,8 @@ void stmmac_selftest_run(struct net_device *dev, ret = -EOPNOTSUPP; if (dev->phydev) ret = phy_loopback(dev->phydev, false, 0); + else if (priv->hw->phylink_pcs) + ret = phylink_pcs_loopback(priv->hw->phylink_pcs, false); if (!ret) break; fallthrough;
diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 59dfe35afa54..a7f78c82913a 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c@@ -997,6 +997,25 @@ int phylink_pcs_pre_init(struct phylink *pl, struct phylink_pcs *pcs) } EXPORT_SYMBOL_GPL(phylink_pcs_pre_init); +/** + * phylink_pcs_loopback() - Enable or disable loopback at the PCS + * @pcs: a pointer to a &struct phylink_pcs. + * @enable: true to enable loopback, false to disable + * + * Enable or disable loopback mode at the PCS level. This is used by MAC + * drivers for selftest purposes when no external PHY is present. + * + * Returns 0 on success, negative error code on failure. + */ +int phylink_pcs_loopback(struct phylink_pcs *pcs, bool enable) +{ + if (pcs->ops->pcs_loopback) + return pcs->ops->pcs_loopback(pcs, enable); + + return -EOPNOTSUPP; +} +EXPORT_SYMBOL_GPL(phylink_pcs_loopback); + static void phylink_mac_config(struct phylink *pl, const struct phylink_link_state *state) {
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index 2bc0db3d52ac..66c7016d4acd 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h@@ -518,6 +518,7 @@ struct phylink_pcs { * the MAC. * @pcs_pre_init: configure PCS components necessary for MAC hardware * initialization e.g. RX clock for stmmac. + * @pcs_loopback: enable/disable loopback mode at the PCS. */ struct phylink_pcs_ops { int (*pcs_validate)(struct phylink_pcs *pcs, unsigned long *supported,
@@ -542,6 +543,7 @@ struct phylink_pcs_ops { void (*pcs_disable_eee)(struct phylink_pcs *pcs); void (*pcs_enable_eee)(struct phylink_pcs *pcs); int (*pcs_pre_init)(struct phylink_pcs *pcs); + int (*pcs_loopback)(struct phylink_pcs *pcs, bool enable); }; #if 0 /* For kernel-doc purposes only. */
@@ -717,8 +719,22 @@ void pcs_enable_eee(struct phylink_pcs *pcs); */ int pcs_pre_init(struct phylink_pcs *pcs); +/** + * pcs_loopback() - Enable or disable loopback at the PCS + * @pcs: a pointer to a &struct phylink_pcs. + * @enable: true to enable loopback, false to disable + * + * Enable or disable loopback mode at the PCS level. This is used by MAC + * drivers for selftest purposes when no external PHY is present. + * + * Returns 0 on success, or a negative error code on failure. + */ +int pcs_loopback(struct phylink_pcs *pcs, bool enable); + #endif +int phylink_pcs_loopback(struct phylink_pcs *pcs, bool enable); + struct phylink *phylink_create(struct phylink_config *, const struct fwnode_handle *, phy_interface_t,
base-commit: 1df10cef2d1e7f9f2fb7eddb67fc70d3abf101f9 -- 2.34.1