net: phy: fix a bug in get_phy_c45_ids

When probing devices-in-package for a c45 phy, device zero is the last
device to probe, however, if driver reads 0 from device zero,
c45_ids->devices_in_package is set to '0', the loop condition of probing
will be matched again, see codes below:

for (i = 1;i < num_ids && c45_ids->devices_in_package == 0;i++)

driver will run in a dead loop.

This patch restructures the bug and confusing loop, it provides a helper
function get_phy_c45_devs_in_pkg which to read devices-in-package registers
of a MMD, and rewrites the loop with using the helper function.
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy_device.c

@@ -205,6 +205,37 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, int phy_id,
 }
 EXPORT_SYMBOL(phy_device_create);
 
+/* get_phy_c45_devs_in_pkg - reads a MMD's devices in package registers.
+ * @bus: the target MII bus
+ * @addr: PHY address on the MII bus
+ * @dev_addr: MMD address in the PHY.
+ * @devices_in_package: where to store the devices in package information.
+ *
+ * Description: reads devices in package registers of a MMD at @dev_addr
+ * from PHY at @addr on @bus.
+ *
+ * Returns: 0 on success, -EIO on failure.
+ */
+static int get_phy_c45_devs_in_pkg(struct mii_bus *bus, int addr, int dev_addr,
+				   u32 *devices_in_package)
+{
+	int phy_reg, reg_addr;
+
+	reg_addr = MII_ADDR_C45 | dev_addr << 16 | MDIO_DEVS2;
+	phy_reg = mdiobus_read(bus, addr, reg_addr);
+	if (phy_reg < 0)
+		return -EIO;
+	*devices_in_package = (phy_reg & 0xffff) << 16;
+
+	reg_addr = MII_ADDR_C45 | dev_addr << 16 | MDIO_DEVS1;
+	phy_reg = mdiobus_read(bus, addr, reg_addr);
+	if (phy_reg < 0)
+		return -EIO;
+	*devices_in_package |= (phy_reg & 0xffff);
+
+	return 0;
+}
+
 /**
  * get_phy_c45_ids - reads the specified addr for its 802.3-c45 IDs.
  * @bus: the target MII bus
@@ -223,38 +254,31 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
 	int phy_reg;
 	int i, reg_addr;
 	const int num_ids = ARRAY_SIZE(c45_ids->device_ids);
+	u32 *devs = &c45_ids->devices_in_package;
 
-	/* Find first non-zero Devices In package.  Device
-	 * zero is reserved, so don't probe it.
+	/* Find first non-zero Devices In package. Device zero is reserved
+	 * for 802.3 c45 complied PHYs, so don't probe it at first.
 	 */
-	for (i = 1;
-	     i < num_ids && c45_ids->devices_in_package == 0;
-	     i++) {
-retry:		reg_addr = MII_ADDR_C45 | i << 16 | MDIO_DEVS2;
-		phy_reg = mdiobus_read(bus, addr, reg_addr);
-		if (phy_reg < 0)
-			return -EIO;
-		c45_ids->devices_in_package = (phy_reg & 0xffff) << 16;
-
-		reg_addr = MII_ADDR_C45 | i << 16 | MDIO_DEVS1;
-		phy_reg = mdiobus_read(bus, addr, reg_addr);
+	for (i = 1; i < num_ids && *devs == 0; i++) {
+		phy_reg = get_phy_c45_devs_in_pkg(bus, addr, i, devs);
 		if (phy_reg < 0)
 			return -EIO;
-		c45_ids->devices_in_package |= (phy_reg & 0xffff);
 
-		if ((c45_ids->devices_in_package & 0x1fffffff) == 0x1fffffff) {
-			if (i) {
+		if ((*devs & 0x1fffffff) == 0x1fffffff) {
 			/*  If mostly Fs, there is no device there,
 			 *  then let's continue to probe more, as some
 			 *  10G PHYs have zero Devices In package,
 			 *  e.g. Cortina CS4315/CS4340 PHY.
 			 */
-				i = 0;
-				goto retry;
-			} else {
+			phy_reg = get_phy_c45_devs_in_pkg(bus, addr, 0, devs);
+			if (phy_reg < 0)
+				return -EIO;
 			/* no device there, let's get out of here */
+			if ((*devs & 0x1fffffff) == 0x1fffffff) {
 				*phy_id = 0xffffffff;
 				return 0;
+			} else {
+				break;
 			}
 		}
 	}