[PATCH net-next v5 4/9] net: pcs: xpcs: re-initiate clause 37 Auto-negotiation

[Choong Yong Liang <yong.liang.choong@xxxxxxxxxxxxxxx>]

According to the XPCS datasheet, a soft reset is required to initiate
Clause 37 auto-negotiation when the XPCS switches interface modes.

When the interface mode is set to 2500BASE-X, Clause 37 Auto-Negotiation
is turned off.

Subsequently, when the interface mode switches from 2500BASE-X to SGMII,
re-initiating Clause 37 auto-negotiation is required for the SGMII
interface mode to function properly.

Signed-off-by: Choong Yong Liang <yong.liang.choong@xxxxxxxxxxxxxxx>
---
 drivers/net/pcs/pcs-xpcs.c | 62 +++++++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 52a7757ee419..cf1ed89d6418 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -848,6 +848,60 @@ static int xpcs_config_2500basex(struct dw_xpcs *xpcs)
 	return xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_MMD_CTRL, ret);
 }
 
+static int xpcs_switch_to_aneg_c37_sgmii(const struct xpcs_compat *compat,
+					 struct dw_xpcs *xpcs,
+					 unsigned int neg_mode)
+{
+	bool an_c37_enabled;
+	int ret, mdio_ctrl;
+
+	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
+		mdio_ctrl = xpcs_read(xpcs, MDIO_MMD_VEND2, DW_VR_MII_MMD_CTRL);
+		if (mdio_ctrl < 0)
+			return mdio_ctrl;
+
+		an_c37_enabled = mdio_ctrl & AN_CL37_EN;
+		if (!an_c37_enabled) {
+			//Perform soft reset to initiate C37 auto-negotiation
+			ret = xpcs_soft_reset(xpcs, compat);
+			if (ret)
+				return ret;
+		}
+	}
+	return 0;
+}
+
+static int xpcs_switch_interface_mode(const struct xpcs_compat *compat,
+				      struct dw_xpcs *xpcs,
+				      phy_interface_t interface,
+				      unsigned int neg_mode)
+{
+	int ret;
+
+	if (xpcs->dev_flag == DW_DEV_TXGBE) {
+		ret = txgbe_xpcs_switch_mode(xpcs, interface);
+		if (ret)
+			return ret;
+	} else {
+		if (xpcs->interface != interface) {
+			xpcs->interface = interface;
+
+			switch (compat->an_mode) {
+			case DW_AN_C37_SGMII:
+				ret = xpcs_switch_to_aneg_c37_sgmii(compat,
+								    xpcs,
+								    neg_mode);
+				if (ret)
+					return ret;
+				break;
+			default:
+				return 0;
+			}
+		}
+	}
+	return 0;
+}
+
 int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 		   const unsigned long *advertising, unsigned int neg_mode)
 {
@@ -858,11 +912,9 @@ int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 	if (!compat)
 		return -ENODEV;
 
-	if (xpcs->dev_flag == DW_DEV_TXGBE) {
-		ret = txgbe_xpcs_switch_mode(xpcs, interface);
-		if (ret)
-			return ret;
-	}
+	ret = xpcs_switch_interface_mode(compat, xpcs, interface, neg_mode);
+	if (ret)
+		return ret;
 
 	switch (compat->an_mode) {
 	case DW_10GBASER:
-- 
2.34.1