fs_enet/mii-fec.c: fix MII speed calculation

The MII speed calculation was based on the CPU clock (ppc_proc_freq),
but for MPC512x we must use the bus clock instead.

This patch makes it use the correct clock and makes sure we don't
clobber reserved bits in the MII_SPEED register.
Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: <netdev@vger.kernel.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/fs_enet/mii-fec.c

@@ -36,6 +36,7 @@
 #include <asm/pgtable.h>
 #include <asm/irq.h>
 #include <asm/uaccess.h>
+#include <asm/mpc5xxx.h>
 
 #include "fs_enet.h"
 #include "fec.h"
@@ -103,11 +104,11 @@ static int fs_enet_fec_mii_reset(struct mii_bus *bus)
 static int __devinit fs_enet_mdio_probe(struct of_device *ofdev,
                                         const struct of_device_id *match)
 {
-	struct device_node *np = NULL;
 	struct resource res;
 	struct mii_bus *new_bus;
 	struct fec_info *fec;
-	int ret = -ENOMEM, i;
+	int (*get_bus_freq)(struct device_node *) = match->data;
+	int ret = -ENOMEM, clock, speed;
 
 	new_bus = mdiobus_alloc();
 	if (!new_bus)
@@ -133,13 +134,35 @@ static int __devinit fs_enet_mdio_probe(struct of_device *ofdev,
 	if (!fec->fecp)
 		goto out_fec;
 
-	fec->mii_speed = ((ppc_proc_freq + 4999999) / 5000000) << 1;
+	if (get_bus_freq) {
+		clock = get_bus_freq(ofdev->node);
+		if (!clock) {
+			/* Use maximum divider if clock is unknown */
+			dev_warn(&ofdev->dev, "could not determine IPS clock\n");
+			clock = 0x3F * 5000000;
+		}
+	} else
+		clock = ppc_proc_freq;
+
+	/*
+	 * Scale for a MII clock <= 2.5 MHz
+	 * Note that only 6 bits (25:30) are available for MII speed.
+	 */
+	speed = (clock + 4999999) / 5000000;
+	if (speed > 0x3F) {
+		speed = 0x3F;
+		dev_err(&ofdev->dev,
+			"MII clock (%d Hz) exceeds max (2.5 MHz)\n",
+			clock / speed);
+	}
+
+	fec->mii_speed = speed << 1;
 
 	setbits32(&fec->fecp->fec_r_cntrl, FEC_RCNTRL_MII_MODE);
 	setbits32(&fec->fecp->fec_ecntrl, FEC_ECNTRL_PINMUX |
 	                                  FEC_ECNTRL_ETHER_EN);
 	out_be32(&fec->fecp->fec_ievent, FEC_ENET_MII);
-	out_be32(&fec->fecp->fec_mii_speed, fec->mii_speed);
+	clrsetbits_be32(&fec->fecp->fec_mii_speed, 0x7E, fec->mii_speed);
 
 	new_bus->phy_mask = ~0;
 	new_bus->irq = kmalloc(sizeof(int) * PHY_MAX_ADDR, GFP_KERNEL);
@@ -188,6 +211,12 @@ static struct of_device_id fs_enet_mdio_fec_match[] = {
 	{
 		.compatible = "fsl,pq1-fec-mdio",
 	},
+#if defined(CONFIG_PPC_MPC512x)
+	{
+		.compatible = "fsl,mpc5121-fec-mdio",
+		.data = mpc5xxx_get_bus_frequency,
+	},
+#endif
 	{},
 };