net: mdio: ipq8064: enlarge sleep after read/write operation

With the use of the qca8k dsa driver, some problem arised related to
port status detection. With a load on a specific port (for example a
simple speed test), the driver starts to behave in a strange way and
garbage data is produced. To address this, enlarge the sleep delay and
address a bug for the reg offset 31 that require additional delay for
this specific reg.
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mdio/mdio-ipq8064.c

@@ -65,7 +65,7 @@ ipq8064_mdio_read(struct mii_bus *bus, int phy_addr, int reg_offset)
 		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);
 
 	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
-	usleep_range(8, 10);
+	usleep_range(10, 13);
 
 	err = ipq8064_mdio_wait_busy(priv);
 	if (err)
@@ -91,7 +91,14 @@ ipq8064_mdio_write(struct mii_bus *bus, int phy_addr, int reg_offset, u16 data)
 		   ((reg_offset << MII_REG_SHIFT) & MII_REG_MASK);
 
 	regmap_write(priv->base, MII_ADDR_REG_ADDR, miiaddr);
-	usleep_range(8, 10);
+
+	/* For the specific reg 31 extra time is needed or the next
+	 * read will produce garbage data.
+	 */
+	if (reg_offset == 31)
+		usleep_range(30, 43);
+	else
+		usleep_range(10, 13);
 
 	return ipq8064_mdio_wait_busy(priv);
 }