[PATCH net-next v7 2/7] net: pcs: xpcs: re-initiate clause 37 Auto-negotiation

[Choong Yong Liang <yong.liang.choong@linux.intel.com>]

The xpcs_switch_interface_mode function was introduced to handle
interface switching.

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@linux.intel.com>
---
 drivers/net/pcs/pcs-xpcs-wx.c |  4 +--
 drivers/net/pcs/pcs-xpcs.c    | 60 ++++++++++++++++++++++++++++++++---
 2 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs-wx.c b/drivers/net/pcs/pcs-xpcs-wx.c
index fc52f7aa5f59..f73ab04d09f0 100644
--- a/drivers/net/pcs/pcs-xpcs-wx.c
+++ b/drivers/net/pcs/pcs-xpcs-wx.c
@@ -172,11 +172,9 @@ int txgbe_xpcs_switch_mode(struct dw_xpcs *xpcs, phy_interface_t interface)
 		return 0;
 	}
 
-	if (xpcs->interface == interface && !txgbe_xpcs_mode_quirk(xpcs))
+	if (!txgbe_xpcs_mode_quirk(xpcs))
 		return 0;
 
-	xpcs->interface = interface;
-
 	ret = txgbe_pcs_poll_power_up(xpcs);
 	if (ret < 0)
 		return ret;
diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 1faa37f0e7b9..fb3d1548a8e0 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -817,6 +817,58 @@ static int xpcs_config_2500basex(struct dw_xpcs *xpcs)
 			   BMCR_SPEED1000);
 }
 
+static int xpcs_switch_to_aneg_c37_sgmii(const struct dw_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, MII_BMCR);
+		if (mdio_ctrl < 0)
+			return mdio_ctrl;
+
+		an_c37_enabled = mdio_ctrl & BMCR_ANENABLE;
+		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 dw_xpcs_compat *compat,
+				      struct dw_xpcs *xpcs,
+				      phy_interface_t interface,
+				      unsigned int neg_mode)
+{
+	int ret = 0;
+
+	if (xpcs->interface != interface) {
+		if (xpcs->info.pma == WX_TXGBE_XPCS_PMA_10G_ID) {
+			ret = txgbe_xpcs_switch_mode(xpcs, interface);
+		} else {
+			switch (compat->an_mode) {
+			case DW_AN_C37_SGMII:
+				ret = xpcs_switch_to_aneg_c37_sgmii(compat, xpcs, neg_mode);
+				break;
+			default:
+				break;
+			}
+		}
+
+		if (ret)
+			return ret;
+
+		xpcs->interface = interface;
+	}
+
+	return 0;
+}
+
 static int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 			  const unsigned long *advertising,
 			  unsigned int neg_mode)
@@ -828,11 +880,11 @@ static int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 	if (!compat)
 		return -ENODEV;
 
-	if (xpcs->info.pma == WX_TXGBE_XPCS_PMA_10G_ID) {
-		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;
 
+	if (xpcs->info.pma == WX_TXGBE_XPCS_PMA_10G_ID) {
 		/* Wangxun devices need backplane CL37 AN enabled for
 		 * SGMII and 1000base-X
 		 */
-- 
2.34.1