[PATCH net-next v9 2/6] 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 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.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index e32dec4b812e..3d1bd5aac093 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -602,12 +602,33 @@ static void xpcs_get_interfaces(struct dw_xpcs *xpcs, unsigned long *interfaces)
 		__set_bit(compat->interface, interfaces);
 }
 
+static int xpcs_switch_interface_mode(struct dw_xpcs *xpcs,
+				      phy_interface_t interface)
+{
+	int ret = 0;
+
+	if (xpcs->info.pma == WX_TXGBE_XPCS_PMA_10G_ID) {
+		ret = txgbe_xpcs_switch_mode(xpcs, interface);
+	} else if (xpcs->interface != interface) {
+		if (interface == PHY_INTERFACE_MODE_SGMII)
+			xpcs->need_reset = true;
+		xpcs->interface = interface;
+	}
+
+	return ret;
+}
+
 static void xpcs_pre_config(struct phylink_pcs *pcs, phy_interface_t interface)
 {
 	struct dw_xpcs *xpcs = phylink_pcs_to_xpcs(pcs);
 	const struct dw_xpcs_compat *compat;
 	int ret;
 
+	ret = xpcs_switch_interface_mode(xpcs, interface);
+	if (ret)
+		dev_err(&xpcs->mdiodev->dev, "switch interface failed: %pe\n",
+			ERR_PTR(ret));
+
 	if (!xpcs->need_reset)
 		return;
 
@@ -799,10 +820,6 @@ static int xpcs_do_config(struct dw_xpcs *xpcs, phy_interface_t interface,
 		return -ENODEV;
 
 	if (xpcs->info.pma == WX_TXGBE_XPCS_PMA_10G_ID) {
-		ret = txgbe_xpcs_switch_mode(xpcs, interface);
-		if (ret)
-			return ret;
-
 		/* Wangxun devices need backplane CL37 AN enabled for
 		 * SGMII and 1000base-X
 		 */
-- 
2.34.1