net: fec: Clear and enable MIB counters on imx51

Both the IMX51 and IMX53 datasheet indicates that the MIB counters
should be cleared during setup. Otherwise random numbers are returned
via ethtool -S.  Add a quirk and a function to do this.

Tested on an IMX51.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec.h

@@ -446,6 +446,10 @@ struct bufdesc_ex {
 #define FEC_QUIRK_HAS_COALESCE		(1 << 13)
 /* Interrupt doesn't wake CPU from deep idle */
 #define FEC_QUIRK_ERR006687		(1 << 14)
+/* The MIB counters should be cleared and enabled during
+ * initialisation.
+ */
+#define FEC_QUIRK_MIB_CLEAR		(1 << 15)
 
 struct bufdesc_prop {
 	int qid;

drivers/net/ethernet/freescale/fec_main.c

@@ -89,10 +89,10 @@ static struct platform_device_id fec_devtype[] = {
 		.driver_data = 0,
 	}, {
 		.name = "imx25-fec",
-		.driver_data = FEC_QUIRK_USE_GASKET,
+		.driver_data = FEC_QUIRK_USE_GASKET | FEC_QUIRK_MIB_CLEAR,
 	}, {
 		.name = "imx27-fec",
-		.driver_data = 0,
+		.driver_data = FEC_QUIRK_MIB_CLEAR,
 	}, {
 		.name = "imx28-fec",
 		.driver_data = FEC_QUIRK_ENET_MAC | FEC_QUIRK_SWAP_FRAME |
@@ -184,6 +184,9 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
 #define FEC_RACC_SHIFT16	BIT(7)
 #define FEC_RACC_OPTIONS	(FEC_RACC_IPDIS | FEC_RACC_PRODIS)
 
+/* MIB Control Register */
+#define FEC_MIB_CTRLSTAT_DISABLE	BIT(31)
+
 /*
  * The 5270/5271/5280/5282/532x RX control register also contains maximum frame
  * size bits. Other FEC hardware does not, so we need to take that into
@@ -2356,6 +2359,21 @@ static int fec_enet_get_sset_count(struct net_device *dev, int sset)
 	}
 }
 
+static void fec_enet_clear_ethtool_stats(struct net_device *dev)
+{
+	struct fec_enet_private *fep = netdev_priv(dev);
+	int i;
+
+	/* Disable MIB statistics counters */
+	writel(FEC_MIB_CTRLSTAT_DISABLE, fep->hwp + FEC_MIB_CTRLSTAT);
+
+	for (i = 0; i < ARRAY_SIZE(fec_stats); i++)
+		writel(0, fep->hwp + fec_stats[i].offset);
+
+	/* Don't disable MIB statistics counters */
+	writel(0, fep->hwp + FEC_MIB_CTRLSTAT);
+}
+
 #else	/* !defined(CONFIG_M5272) */
 #define FEC_STATS_SIZE	0
 static inline void fec_enet_update_ethtool_stats(struct net_device *dev)
@@ -3182,7 +3200,10 @@ static int fec_enet_init(struct net_device *ndev)
 
 	fec_restart(ndev);
 
-	fec_enet_update_ethtool_stats(ndev);
+	if (fep->quirks & FEC_QUIRK_MIB_CLEAR)
+		fec_enet_clear_ethtool_stats(ndev);
+	else
+		fec_enet_update_ethtool_stats(ndev);
 
 	return 0;
 }