ARM: dts: stm32: Do not set eth1addr if KS8851 has EEPROM

In case the KS8851 has external EEPROM attached to it, do not set
eth1addr at all. The network stack will read the MAC out of the
KS8851 and set eth1addr accordingly.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>

board/dhelectronics/dh_stm32mp1/board.c

@@ -81,6 +81,11 @@
  */
 DECLARE_GLOBAL_DATA_PTR;
 
+#define KS_CCR		0x08
+#define KS_CCR_EEPROM	BIT(9)
+#define KS_BE0		BIT(12)
+#define KS_BE1		BIT(13)
+
 int setup_mac_address(void)
 {
 	unsigned char enetaddr[6];
@@ -97,12 +102,39 @@ int setup_mac_address(void)
 	if (off < 0) {
 		/* ethernet1 is not present in the system */
 		skip_eth1 = true;
-	} else {
-		ret = eth_env_get_enetaddr("eth1addr", enetaddr);
-		if (ret)	/* eth1addr is already set */
-			skip_eth1 = true;
+		goto out_set_ethaddr;
+	}
+
+	ret = eth_env_get_enetaddr("eth1addr", enetaddr);
+	if (ret) {
+		/* eth1addr is already set */
+		skip_eth1 = true;
+		goto out_set_ethaddr;
+	}
+
+	ret = fdt_node_check_compatible(gd->fdt_blob, off, "micrel,ks8851-mll");
+	if (ret)
+		goto out_set_ethaddr;
+
+	/*
+	 * KS8851 with EEPROM may use custom MAC from EEPROM, read
+	 * out the KS8851 CCR register to determine whether EEPROM
+	 * is present. If EEPROM is present, it must contain valid
+	 * MAC address.
+	 */
+	u32 reg, ccr;
+	reg = fdt_get_base_address(gd->fdt_blob, off);
+	if (!reg)
+		goto out_set_ethaddr;
+
+	writew(KS_BE0 | KS_BE1 | KS_CCR, reg + 2);
+	ccr = readw(reg);
+	if (ccr & KS_CCR_EEPROM) {
+		skip_eth1 = true;
+		goto out_set_ethaddr;
 	}
 
+out_set_ethaddr:
 	if (skip_eth0 && skip_eth1)
 		return 0;