net: phy: bcm7xx: Correct read from expansion register

Since the driver works in the "legacy" addressing mode, we need to write
to the expansion register (0x17) with bits 11:8 set to 0xf to properly
select the expansion register passed as argument.

Fixes: f68d08c ("net: phy: bcm7xxx: Add EPHY entry for 72165")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230508231749.1681169-1-f.fainelli@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: ffainelli

drivers/net/phy/bcm-phy-lib.h

@@ -40,6 +40,11 @@ static inline int bcm_phy_write_exp_sel(struct phy_device *phydev,
 	return bcm_phy_write_exp(phydev, reg | MII_BCM54XX_EXP_SEL_ER, val);
 }
 
+static inline int bcm_phy_read_exp_sel(struct phy_device *phydev, u16 reg)
+{
+	return bcm_phy_read_exp(phydev, reg | MII_BCM54XX_EXP_SEL_ER);
+}
+
 int bcm54xx_auxctl_write(struct phy_device *phydev, u16 regnum, u16 val);
 int bcm54xx_auxctl_read(struct phy_device *phydev, u16 regnum);
 

drivers/net/phy/bcm7xxx.c

@@ -486,7 +486,7 @@ static int bcm7xxx_16nm_ephy_afe_config(struct phy_device *phydev)
 	bcm_phy_write_misc(phydev, 0x0038, 0x0002, 0xede0);
 
 	/* Read CORE_EXPA9 */
-	tmp = bcm_phy_read_exp(phydev, 0x00a9);
+	tmp = bcm_phy_read_exp_sel(phydev, 0x00a9);
 	/* CORE_EXPA9[6:1] is rcalcode[5:0] */
 	rcalcode = (tmp & 0x7e) / 2;
 	/* Correct RCAL code + 1 is -1% rprogr, LP: +16 */