net: pcs: xpcs: re-initiate clause 37 Auto-negotiation

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>
Link: https://patch.msgid.link/20250227121522.1802832-3-yong.liang.choong@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index e32dec4b812ec1c80eac7d9ef77131177efa4cfe..3d1bd5aac09376deef2179fa958a580b5afcb197 100644 (file)
--- 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
                 */