driver/net/fec: support fixed speed connection

If MAC is directly connected to another MAC (like a switch for example)
we don't need to probe for a phy, autoneogation and so on. We simply
have to setup speed.
Signed-off-by: NHannes Schmelzer <oe5hpm@oevsv.at>
Acked-by: NJoe Hershberger <joe.hershberger@ni.com>

doc/README.fec_mxc

@@ -27,6 +27,11 @@ CONFIG_FEC_MXC_PHYADDR
 	Optional, selects the exact phy address that should be connected
 	and function fecmxc_initialize will try to initialize it.
 
+CONFIG_FEC_FIXED_SPEED
+	Optional, selects a fixed speed on the MAC interface without asking some
+	phy. This is usefull if there is a direct MAC <-> MAC connection, for
+	example if the CPU is connected directly via the RGMII interface to a
+	ethernet-switch.
 
 Reading the ethaddr from the SoC eFuses:
 if CONFIG_FEC_MXC is defined and the U-Boot environment does not contain the

drivers/net/fec_mxc.c

@@ -233,6 +233,7 @@ static int miiphy_restart_aneg(struct eth_device *dev)
 	return ret;
 }
 
+#ifndef CONFIG_FEC_FIXED_SPEED
 static int miiphy_wait_aneg(struct eth_device *dev)
 {
 	uint32_t start;
@@ -260,6 +261,7 @@ static int miiphy_wait_aneg(struct eth_device *dev)
 
 	return 0;
 }
+#endif /* CONFIG_FEC_FIXED_SPEED */
 #endif
 
 static int fec_rx_task_enable(struct fec_priv *fec)
@@ -502,6 +504,8 @@ static int fec_open(struct eth_device *edev)
 		}
 		speed = fec->phydev->speed;
 	}
+#elif CONFIG_FEC_FIXED_SPEED
+	speed = CONFIG_FEC_FIXED_SPEED;
 #else
 	miiphy_wait_aneg(edev);
 	speed = miiphy_speed(edev->name, fec->phy_id);