net: phy: broadcom: add bcm54xx_auxctl_read

Add a helper function to read the AUXCTL register for the BCM54xx.  This
mirrors the bcm54xx_auxctl_write function already present in the code.

Signed-off-by: Jon Mason <jon.mason@broadcom.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/broadcom.c

@@ -30,6 +30,16 @@ MODULE_DESCRIPTION("Broadcom PHY driver");
 MODULE_AUTHOR("Maciej W. Rozycki");
 MODULE_LICENSE("GPL");
 
+static int bcm54xx_auxctl_read(struct phy_device *phydev, u16 regnum)
+{
+	/* The register must be written to both the Shadow Register Select and
+	 * the Shadow Read Register Selector
+	 */
+	phy_write(phydev, MII_BCM54XX_AUX_CTL, regnum |
+		  regnum << MII_BCM54XX_AUXCTL_SHDWSEL_READ_SHIFT);
+	return phy_read(phydev, MII_BCM54XX_AUX_CTL);
+}
+
 static int bcm54xx_auxctl_write(struct phy_device *phydev, u16 regnum, u16 val)
 {
 	return phy_write(phydev, MII_BCM54XX_AUX_CTL, regnum | val);

include/linux/brcmphy.h

@@ -110,6 +110,7 @@
 #define MII_BCM54XX_AUXCTL_MISC_FORCE_AMDIX	0x0200
 #define MII_BCM54XX_AUXCTL_MISC_RDSEL_MISC	0x7000
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MISC	0x0007
+#define MII_BCM54XX_AUXCTL_SHDWSEL_READ_SHIFT	12
 
 #define MII_BCM54XX_AUXCTL_SHDWSEL_MASK	0x0007