net: dsa: mv88e6xxx: don't use PHY_DETECT on internal PHY's

mv88e6xxx_port_ppu_updates() interpretes data in the PORT_STS
register incorrectly for internal ports (ie no PPU). In these
cases, the PHY_DETECT bit indicates link status. This results
in forcing the MAC state whenever the PHY link goes down which
is not intended. As a side effect, LED's configured to show
link status stay lit even though the physical link is down.

Add a check in mac_link_down and mac_link_up to see if it
concerns an external port and only then, look at PPU status.

Fixes: 5d5b231d (net: dsa: mv88e6xxx: use PHY_DETECT in mac_link_up/mac_link_down)
Reported-by: Maarten Zanders <m.zanders@televic.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Maarten Zanders <maarten.zanders@mind.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -750,7 +750,11 @@ static void mv88e6xxx_mac_link_down(struct dsa_switch *ds, int port,
 	ops = chip->info->ops;
 
 	mv88e6xxx_reg_lock(chip);
-	if ((!mv88e6xxx_port_ppu_updates(chip, port) ||
+	/* Internal PHYs propagate their configuration directly to the MAC.
+	 * External PHYs depend on whether the PPU is enabled for this port.
+	 */
+	if (((!mv88e6xxx_phy_is_internal(ds, port) &&
+	      !mv88e6xxx_port_ppu_updates(chip, port)) ||
 	     mode == MLO_AN_FIXED) && ops->port_sync_link)
 		err = ops->port_sync_link(chip, port, mode, false);
 	mv88e6xxx_reg_unlock(chip);
@@ -773,7 +777,12 @@ static void mv88e6xxx_mac_link_up(struct dsa_switch *ds, int port,
 	ops = chip->info->ops;
 
 	mv88e6xxx_reg_lock(chip);
-	if (!mv88e6xxx_port_ppu_updates(chip, port) || mode == MLO_AN_FIXED) {
+	/* Internal PHYs propagate their configuration directly to the MAC.
+	 * External PHYs depend on whether the PPU is enabled for this port.
+	 */
+	if ((!mv88e6xxx_phy_is_internal(ds, port) &&
+	     !mv88e6xxx_port_ppu_updates(chip, port)) ||
+	    mode == MLO_AN_FIXED) {
 		/* FIXME: for an automedia port, should we force the link
 		 * down here - what if the link comes up due to "other" media
 		 * while we're bringing the port up, how is the exclusivity