The dwmac core has no support for SGMII without using its integrated
PCS. Thus, PHY_INTF_SEL_SGMII is only supported when this block is
present, and it makes no sense for stmmac_get_phy_intf_sel() to decode
this.

None of the platform glue users that use stmmac_get_phy_intf_sel()
directly accept PHY_INTF_SEL_SGMII as a valid mode.

Check whether a PCS will be used by the driver for the interface mode,
and if it is the integrated PCS, query the integrated PCS for the
phy_intf_sel_i value to use.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 15 ++++++++++++---
 drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c  |  9 +++++++++
 drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h  |  2 ++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 6c515f9efbe7..5254d9d19ffe 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3135,8 +3135,6 @@ int stmmac_get_phy_intf_sel(phy_interface_t interface)
 		phy_intf_sel = PHY_INTF_SEL_GMII_MII;
 	else if (phy_interface_mode_is_rgmii(interface))
 		phy_intf_sel = PHY_INTF_SEL_RGMII;
-	else if (interface == PHY_INTERFACE_MODE_SGMII)
-		phy_intf_sel = PHY_INTF_SEL_SGMII;
 	else if (interface == PHY_INTERFACE_MODE_RMII)
 		phy_intf_sel = PHY_INTF_SEL_RMII;
 	else if (interface == PHY_INTERFACE_MODE_REVMII)
@@ -3150,13 +3148,24 @@ static int stmmac_prereset_configure(struct stmmac_priv *priv)
 {
 	struct plat_stmmacenet_data *plat_dat = priv->plat;
 	phy_interface_t interface;
+	struct phylink_pcs *pcs;
 	int phy_intf_sel, ret;
 
 	if (!plat_dat->set_phy_intf_sel)
 		return 0;
 
 	interface = plat_dat->phy_interface;
-	phy_intf_sel = stmmac_get_phy_intf_sel(interface);
+
+	/* Check whether this mode uses a PCS */
+	pcs = stmmac_mac_select_pcs(&priv->phylink_config, interface);
+	if (priv->integrated_pcs && pcs == &priv->integrated_pcs->pcs) {
+		/* Request the phy_intf_sel from the integrated PCS */
+		phy_intf_sel = stmmac_integrated_pcs_get_phy_intf_sel(priv,
+								    interface);
+	} else {
+		phy_intf_sel = stmmac_get_phy_intf_sel(interface);
+	}
+
 	if (phy_intf_sel < 0) {
 		netdev_err(priv->dev,
 			   "failed to get phy_intf_sel for %s: %pe\n",
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
index 718e5360fca3..cf7337e9ed3e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.c
@@ -106,6 +106,15 @@ void stmmac_integrated_pcs_irq(struct stmmac_priv *priv, u32 status,
 	}
 }
 
+int stmmac_integrated_pcs_get_phy_intf_sel(struct stmmac_priv *priv,
+					   phy_interface_t interface)
+{
+	if (interface == PHY_INTERFACE_MODE_SGMII)
+		return PHY_INTF_SEL_SGMII;
+
+	return -EINVAL;
+}
+
 int stmmac_integrated_pcs_init(struct stmmac_priv *priv, unsigned int offset,
 			       u32 int_mask)
 {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
index 887c4ff302aa..845bcad9d0f7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
@@ -43,6 +43,8 @@ phylink_pcs_to_stmmac_pcs(struct phylink_pcs *pcs)
 
 void stmmac_integrated_pcs_irq(struct stmmac_priv *priv, u32 status,
 			       struct stmmac_extra_stats *x);
+int stmmac_integrated_pcs_get_phy_intf_sel(struct stmmac_priv *priv,
+					   phy_interface_t interface);
 int stmmac_integrated_pcs_init(struct stmmac_priv *priv, unsigned int offset,
 			       u32 int_mask);
 
-- 
2.47.3