1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index 15c422387028..013525f3c3bd 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -584,6 +584,18 @@ static void gfar_configure_serdes(struct net_device *dev)
         struct gfar_mii __iomem *regs =
                         (void __iomem *)&priv->regs->gfar_mii_regs;
         int tbipa = gfar_read(&priv->regs->tbipa);
+        struct mii_bus *bus = gfar_get_miibus(priv);
+
+        if (bus)
+                mutex_lock(&bus->mdio_lock);
+
+        /* If the link is already up, we must already be ok, and don't need to
+         * configure and reset the TBI<->SerDes link.  Maybe U-Boot configured
+         * everything for us?  Resetting it takes the link down and requires
+         * several seconds for it to come back.
+         */
+        if (gfar_local_mdio_read(regs, tbipa, MII_BMSR) & BMSR_LSTATUS)
+                goto done;
 
         /* Single clk mode, mii mode off(for serdes communication) */
         gfar_local_mdio_write(regs, tbipa, MII_TBICON, TBICON_CLK_SELECT);
@@ -594,6 +606,10 @@ static void gfar_configure_serdes(struct net_device *dev)
 
         gfar_local_mdio_write(regs, tbipa, MII_BMCR, BMCR_ANENABLE |
                         BMCR_ANRESTART | BMCR_FULLDPLX | BMCR_SPEED1000);
+
+        done:
+        if (bus)
+                mutex_unlock(&bus->mdio_lock);
 }
 
 static void init_registers(struct net_device *dev)