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([39.170.101.209]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84e533d1637sm2935168b3a.33.2026.07.27.05.07.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jul 2026 05:07:14 -0700 (PDT) From: Zxyan Zhu To: andrew+netdev@lunn.ch, rmk+kernel@armlinux.org.uk, alexandre.torgue@foss.st.com Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, hkallweit1@gmail.com, mcoquelin.stm32@gmail.com, maxime.chevallier@bootlin.com, netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Zxyan Zhu Subject: [PATCH net-next v2] net: phylink: add phylink_pcs_loopback() method for PCS loopback support Date: Mon, 27 Jul 2026 20:07:04 +0800 Message-Id: <20260727120704.2319467-1-zxyan0222@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some Ethernet MAC drivers (such as stmmac) need to perform PCS-level loopback for selftest purposes when no external PHY is present. Add a new phylink_pcs_loopback() method that allows MAC drivers to request PCS loopback mode through the phylink framework. Implement the pcs_loopback callback in the stmmac integrated PCS using the GMAC_AN_CTRL_ELE register bit. Add a helper function stmmac_selftest_get_pcs() in stmmac selftests to unify PCS lookup across glue driver PCS and integrated PCS. Update the selftest enable/disable paths to use the new helper. Signed-off-by: Zxyan Zhu --- .../net/ethernet/stmicro/stmmac/stmmac_pcs.c | 17 +++++++ .../stmicro/stmmac/stmmac_selftests.c | 51 ++++++++++++++++--- drivers/net/phy/phylink.c | 19 +++++++ include/linux/phylink.h | 16 ++++++ 4 files changed, 95 insertions(+), 8 deletions(-) v2: - Implement pcs_loopback callback in stmmac integrated PCS using GMAC_AN_CTRL_ELE register bit. - Add stmmac_selftest_get_pcs() helper to unify PCS lookup across glue driver PCS and integrated PCS. - Add NULL check in phylink_pcs_loopback() wrapper. v1: https://lore.kernel.org/netdev/20260724085224.3321663-1-zxyan0222@gmail.com/ Note on loopback direction: The pcs_loopback callback uses a simple enable/disable boolean, matching the existing phy_loopback() API. Direction is not needed at this level: selftest loopback is always host-side (TX looped back to RX). The future ethtool user-space loopback API can handle direction selection at a higher layer. Note on phylink_set_loopback() vs phylink_pcs_loopback(): This patch follows the same pattern as phy_loopback() - a direct callback on the PCS object. Keeping the API minimal avoids introducing a new phylink-level loopback abstraction with location enumeration before Björn's ethtool loopback series lands upstream. Once that series is merged, phylink_pcs_loopback() can serve as a building block for a higher-level phylink_set_loopback() if needed. diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c index df37af5ab837..90a21a2f7e87 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c @@ -168,6 +168,22 @@ static void dwmac_integrated_pcs_an_restart(struct phylink_pcs *pcs) } } +static int dwmac_integrated_pcs_loopback(struct phylink_pcs *pcs, bool enable) +{ + struct stmmac_pcs *spcs = phylink_pcs_to_stmmac_pcs(pcs); + void __iomem *an_control = spcs->base + GMAC_AN_CTRL(0); + u32 ctrl; + + ctrl = readl(an_control); + if (enable) + ctrl |= GMAC_AN_CTRL_ELE; + else + ctrl &= ~GMAC_AN_CTRL_ELE; + writel(ctrl, an_control); + + return 0; +} + static const struct phylink_pcs_ops dwmac_integrated_pcs_ops = { .pcs_inband_caps = dwmac_integrated_pcs_inband_caps, .pcs_enable = dwmac_integrated_pcs_enable, @@ -175,6 +191,7 @@ static const struct phylink_pcs_ops dwmac_integrated_pcs_ops = { .pcs_get_state = dwmac_integrated_pcs_get_state, .pcs_config = dwmac_integrated_pcs_config, .pcs_an_restart = dwmac_integrated_pcs_an_restart, + .pcs_loopback = dwmac_integrated_pcs_loopback, }; void stmmac_integrated_pcs_irq(struct stmmac_priv *priv, u32 status, diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c index 29e824bd90ca..77a457b2fa5c 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c @@ -19,6 +19,7 @@ #include #include #include "stmmac.h" +#include "stmmac_pcs.h" struct stmmachdr { __be32 version; @@ -374,23 +375,51 @@ static int stmmac_test_mac_loopback(struct stmmac_priv *priv) return __stmmac_test_loopback(priv, &attr); } +static struct phylink_pcs *stmmac_selftest_get_pcs(struct stmmac_priv *priv) +{ + /* Try glue driver's PCS first, then the integrated PCS. */ + if (priv->hw->phylink_pcs) + return priv->hw->phylink_pcs; + + if (priv->integrated_pcs) + return &priv->integrated_pcs->pcs; + + return NULL; +} + 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 = stmmac_selftest_get_pcs(priv); + 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 +2015,9 @@ void stmmac_selftest_run(struct net_device *dev, ret = -EOPNOTSUPP; if (dev->phydev) ret = phy_loopback(dev->phydev, true, 0); + else + ret = phylink_pcs_loopback(stmmac_selftest_get_pcs(priv), + true); if (!ret) break; fallthrough; @@ -2019,6 +2051,9 @@ void stmmac_selftest_run(struct net_device *dev, ret = -EOPNOTSUPP; if (dev->phydev) ret = phy_loopback(dev->phydev, false, 0); + else + ret = phylink_pcs_loopback(stmmac_selftest_get_pcs(priv), + false); if (!ret) break; fallthrough; diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c index 59dfe35afa54..69242caffaef 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 && 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