net/fsl: treat fsl,erratum-a011043

When fsl,erratum-a011043 is set, adjust for erratum A011043:
MDIO reads to internal PCS registers may result in having
the MDIO_CFG[MDIO_RD_ER] bit set, even when there is no
error and read data (MDIO_DATA[MDIO_DATA]) is correct.
Software may get false read error when reading internal
PCS registers through MDIO. As a workaround, all internal
MDIO accesses should ignore the MDIO_CFG[MDIO_RD_ER] bit.

Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/xgmac_mdio.c

@@ -49,6 +49,7 @@ struct tgec_mdio_controller {
 struct mdio_fsl_priv {
 	struct	tgec_mdio_controller __iomem *mdio_base;
 	bool	is_little_endian;
+	bool	has_a011043;
 };
 
 static u32 xgmac_read32(void __iomem *regs,
@@ -226,7 +227,8 @@ static int xgmac_mdio_read(struct mii_bus *bus, int phy_id, int regnum)
 		return ret;
 
 	/* Return all Fs if nothing was there */
-	if (xgmac_read32(&regs->mdio_stat, endian) & MDIO_STAT_RD_ER) {
+	if ((xgmac_read32(&regs->mdio_stat, endian) & MDIO_STAT_RD_ER) &&
+	    !priv->has_a011043) {
 		dev_err(&bus->dev,
 			"Error while reading PHY%d reg at %d.%hhu\n",
 			phy_id, dev_addr, regnum);
@@ -274,6 +276,9 @@ static int xgmac_mdio_probe(struct platform_device *pdev)
 	priv->is_little_endian = of_property_read_bool(pdev->dev.of_node,
 						       "little-endian");
 
+	priv->has_a011043 = of_property_read_bool(pdev->dev.of_node,
+						  "fsl,erratum-a011043");
+
 	ret = of_mdiobus_register(bus, np);
 	if (ret) {
 		dev_err(&pdev->dev, "cannot register MDIO bus\n");