diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
index 2fd2620ebed6..767994061ea8 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
@@ -157,6 +157,37 @@ static int stm32_dwmac_init(struct plat_stmmacenet_data *plat_dat, bool resume)
 	return stm32_dwmac_clk_enable(dwmac, resume);
 }
 
+static int stm32mp1_select_ethck_external(struct plat_stmmacenet_data *plat_dat)
+{
+	struct stm32_dwmac *dwmac = plat_dat->bsp_priv;
+
+	switch (plat_dat->mac_interface) {
+	case PHY_INTERFACE_MODE_MII:
+		dwmac->enable_eth_ck = dwmac->ext_phyclk;
+		return 0;
+	case PHY_INTERFACE_MODE_GMII:
+		dwmac->enable_eth_ck = dwmac->eth_clk_sel_reg ||
+				       dwmac->ext_phyclk;
+		return 0;
+	case PHY_INTERFACE_MODE_RMII:
+		dwmac->enable_eth_ck = dwmac->eth_ref_clk_sel_reg ||
+				       dwmac->ext_phyclk;
+		return 0;
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_ID:
+	case PHY_INTERFACE_MODE_RGMII_RXID:
+	case PHY_INTERFACE_MODE_RGMII_TXID:
+		dwmac->enable_eth_ck = dwmac->eth_clk_sel_reg ||
+				       dwmac->ext_phyclk;
+		return 0;
+	default:
+		dwmac->enable_eth_ck = false;
+		dev_err(dwmac->dev, "Mode %s not supported",
+			phy_modes(plat_dat->mac_interface));
+		return -EINVAL;
+	}
+}
+
 static int stm32mp1_validate_ethck_rate(struct plat_stmmacenet_data *plat_dat)
 {
 	struct stm32_dwmac *dwmac = plat_dat->bsp_priv;
@@ -194,28 +225,25 @@ static int stm32mp1_set_mode(struct plat_stmmacenet_data *plat_dat)
 	u32 reg = dwmac->mode_reg;
 	int val, ret;
 
-	dwmac->enable_eth_ck = false;
+	ret = stm32mp1_select_ethck_external(plat_dat);
+	if (ret)
+		return ret;
+
 	switch (plat_dat->mac_interface) {
 	case PHY_INTERFACE_MODE_MII:
-		if (dwmac->ext_phyclk)
-			dwmac->enable_eth_ck = true;
 		val = SYSCFG_PMCR_ETH_SEL_MII;
 		pr_debug("SYSCFG init : PHY_INTERFACE_MODE_MII\n");
 		break;
 	case PHY_INTERFACE_MODE_GMII:
 		val = SYSCFG_PMCR_ETH_SEL_GMII;
-		if (dwmac->eth_clk_sel_reg || dwmac->ext_phyclk) {
-			dwmac->enable_eth_ck = true;
+		if (dwmac->enable_eth_ck)
 			val |= SYSCFG_PMCR_ETH_CLK_SEL;
-		}
 		pr_debug("SYSCFG init : PHY_INTERFACE_MODE_GMII\n");
 		break;
 	case PHY_INTERFACE_MODE_RMII:
 		val = SYSCFG_PMCR_ETH_SEL_RMII;
-		if (dwmac->eth_ref_clk_sel_reg || dwmac->ext_phyclk) {
-			dwmac->enable_eth_ck = true;
+		if (dwmac->enable_eth_ck)
 			val |= SYSCFG_PMCR_ETH_REF_CLK_SEL;
-		}
 		pr_debug("SYSCFG init : PHY_INTERFACE_MODE_RMII\n");
 		break;
 	case PHY_INTERFACE_MODE_RGMII:
@@ -223,10 +251,8 @@ static int stm32mp1_set_mode(struct plat_stmmacenet_data *plat_dat)
 	case PHY_INTERFACE_MODE_RGMII_RXID:
 	case PHY_INTERFACE_MODE_RGMII_TXID:
 		val = SYSCFG_PMCR_ETH_SEL_RGMII;
-		if (dwmac->eth_clk_sel_reg || dwmac->ext_phyclk) {
-			dwmac->enable_eth_ck = true;
+		if (dwmac->enable_eth_ck)
 			val |= SYSCFG_PMCR_ETH_CLK_SEL;
-		}
 		pr_debug("SYSCFG init : PHY_INTERFACE_MODE_RGMII\n");
 		break;
 	default: