net: dsa: mv88e6xxx: Clear the PDOWN bit on setup

Some of the vendor-specific bootloaders set up this part
of the initialization for us, so this was never added.
However, since upstream bootloaders don't initialize the
chip specifically, they leave the fiber MII's PDOWN flag
set, which means that the CPU port doesn't connect.

This patch checks whether this flag has been clear prior
by something else, and if not make us clear it.
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Patrick Uiterwijk <patrick@puiterwijk.org>
Tested-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx.c

@@ -2296,6 +2296,25 @@ static int _mv88e6xxx_phy_page_read(struct dsa_switch *ds, int port, int page,
 	return ret;
 }
 
+static int mv88e6xxx_power_on_serdes(struct dsa_switch *ds)
+{
+	int ret;
+
+	ret = _mv88e6xxx_phy_page_read(ds, REG_FIBER_SERDES, PAGE_FIBER_SERDES,
+				       MII_BMCR);
+	if (ret < 0)
+		return ret;
+
+	if (ret & BMCR_PDOWN) {
+		ret &= ~BMCR_PDOWN;
+		ret = _mv88e6xxx_phy_page_write(ds, REG_FIBER_SERDES,
+						PAGE_FIBER_SERDES, MII_BMCR,
+						ret);
+	}
+
+	return ret;
+}
+
 static int mv88e6xxx_setup_port(struct dsa_switch *ds, int port)
 {
 	struct mv88e6xxx_priv_state *ps = ds_to_priv(ds);
@@ -2399,6 +2418,23 @@ static int mv88e6xxx_setup_port(struct dsa_switch *ds, int port)
 			goto abort;
 	}
 
+	/* If this port is connected to a SerDes, make sure the SerDes is not
+	 * powered down.
+	 */
+	if (mv88e6xxx_6352_family(ds)) {
+		ret = _mv88e6xxx_reg_read(ds, REG_PORT(port), PORT_STATUS);
+		if (ret < 0)
+			goto abort;
+		ret &= PORT_STATUS_CMODE_MASK;
+		if ((ret == PORT_STATUS_CMODE_100BASE_X) ||
+		    (ret == PORT_STATUS_CMODE_1000BASE_X) ||
+		    (ret == PORT_STATUS_CMODE_SGMII)) {
+			ret = mv88e6xxx_power_on_serdes(ds);
+			if (ret < 0)
+				goto abort;
+		}
+	}
+
 	/* Port Control 2: don't force a good FCS, set the maximum frame size to
 	 * 10240 bytes, disable 802.1q tags checking, don't discard tagged or
 	 * untagged frames on this port, do a destination address lookup on all

drivers/net/dsa/mv88e6xxx.h

@@ -28,6 +28,10 @@
 #define SMI_CMD_OP_45_READ_DATA_INC	((3 << 10) | SMI_CMD_BUSY)
 #define SMI_DATA		0x01
 
+/* Fiber/SERDES Registers are located at SMI address F, page 1 */
+#define REG_FIBER_SERDES	0x0f
+#define PAGE_FIBER_SERDES	0x01
+
 #define REG_PORT(p)		(0x10 + (p))
 #define PORT_STATUS		0x00
 #define PORT_STATUS_PAUSE_EN	BIT(15)
@@ -45,6 +49,10 @@
 #define PORT_STATUS_MGMII	BIT(6) /* 6185 */
 #define PORT_STATUS_TX_PAUSED	BIT(5)
 #define PORT_STATUS_FLOW_CTRL	BIT(4)
+#define PORT_STATUS_CMODE_MASK	0x0f
+#define PORT_STATUS_CMODE_100BASE_X	0x8
+#define PORT_STATUS_CMODE_1000BASE_X	0x9
+#define PORT_STATUS_CMODE_SGMII		0xa
 #define PORT_PCS_CTRL		0x01
 #define PORT_PCS_CTRL_RGMII_DELAY_RXCLK	BIT(15)
 #define PORT_PCS_CTRL_RGMII_DELAY_TXCLK	BIT(14)