mdio: add subcommand 'up' to check for link

- performs a phy startup sequence and checks result
- returns 0 when link is up, 1 if no link could be established

BugzID: 55019

cmd/mdio.c

@@ -24,6 +24,29 @@ static uint last_devad_hi;
 static uint last_reg_lo;
 static uint last_reg_hi;
 
+
+static int mdio_wait_for_link(struct phy_device *phydev, struct mii_dev *bus)
+{
+	int link;
+	int res;
+
+	printf("waiting for link up on %s\n", bus->name);
+	
+	phy_startup(phydev);
+
+	link = phydev->link;
+	if (link) {
+		printf("link up\n");
+		res = 0;
+	}
+	else {
+		printf("no link\n");
+		res = 1;
+	}
+
+	return res;
+}
+
 static int extract_range(char *input, int *plo, int *phi)
 {
 	char *end;
@@ -191,6 +214,7 @@ static int do_mdio(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	struct mii_dev *bus;
 	struct phy_device *phydev = NULL;
 	int extended = 0;
+	int res = 0;
 
 	if (argc < 2)
 		return CMD_RET_USAGE;
@@ -213,7 +237,14 @@ static int do_mdio(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	if (flag & CMD_FLAG_REPEAT)
 		op[0] = last_op[0];
 
-	if (strlen(argv[1]) > 1) {
+	if (strcmp(argv[1], "up") == 0)	{
+		if (argc >= 3) {
+			phydev = mdio_phydev_for_ethname(argv[2]);
+		} else {
+			return CMD_RET_USAGE;
+		}
+	}
+	else if (strlen(argv[1]) > 1) {
 		op[1] = argv[1][1];
 		if (op[1] == 'x') {
 			phydev = mdio_phydev_for_ethname(argv[2]);
@@ -274,6 +305,10 @@ static int do_mdio(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 		mdio_read_ranges(phydev, bus, addrlo, addrhi, devadlo, devadhi,
 				 reglo, reghi, extended);
 		break;
+	
+	case 'u':
+		res = mdio_wait_for_link(phydev, bus);
+		break;
 	}
 
 	/*
@@ -288,7 +323,7 @@ static int do_mdio(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	last_reg_hi  = reghi;
 	last_data    = data;
 
-	return 0;
+	return res;
 }
 
 /***************************************************/
@@ -305,6 +340,7 @@ U_BOOT_CMD(
 		"read PHY's extended register at <devad>.<reg>\n"
 	"mdio wx <phydev> [<devad>.]<reg> <data> - "
 		"write PHY's extended register at <devad>.<reg>\n"
+	"mdio up <phydev> - wait for PHY link to become ready (up)\n"
 	"<phydev> may be:\n"
 	"   <busname>  <addr>\n"
 	"   <addr>\n"