[PATCH v2] phy: micrel.c: Enable ksz9031 energy-detect power-down mode

[Mike Looijmans]

Set bit 0 in register 1C.23 to enable the EDPD feature of the
KSZ9031 PHY. This reduces power consumption when the link is
down.

Signed-off-by: Mike Looijmans <mike.looijm...@topic.nl>
---
v2: Unconditionally enable EDPD mode

 drivers/net/phy/micrel.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 885ac9c..081df68 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -439,6 +439,10 @@ static int ksz9021_config_init(struct phy_device *phydev)
 #define MII_KSZ9031RN_TX_DATA_PAD_SKEW 6
 #define MII_KSZ9031RN_CLK_PAD_SKEW     8
 
+/* MMD Address 0x1C */
+#define MII_KSZ9031RN_EDPD             0x23
+#define MII_KSZ9031RN_EDPD_ENABLE      BIT(0)
+
 static int ksz9031_extended_write(struct phy_device *phydev,
                                  u8 mode, u32 dev_addr, u32 regnum, u16 val)
 {
@@ -510,6 +514,18 @@ static int ksz9031_center_flp_timing(struct phy_device 
*phydev)
        return genphy_restart_aneg(phydev);
 }
 
+/* Enable energy-detect power-down mode */
+static int ksz9031_enable_edpd(struct phy_device *phydev)
+{
+       int reg;
+
+       reg = ksz9031_extended_read(phydev, OP_DATA, 0x1C, MII_KSZ9031RN_EDPD);
+       if (reg < 0)
+               return reg;
+       return ksz9031_extended_write(phydev, OP_DATA, 0x1C, MII_KSZ9031RN_EDPD,
+                                     reg | MII_KSZ9031RN_EDPD_ENABLE);
+}
+
 static int ksz9031_config_init(struct phy_device *phydev)
 {
        const struct device *dev = &phydev->mdio.dev;
@@ -525,6 +541,11 @@ static int ksz9031_config_init(struct phy_device *phydev)
        };
        static const char *control_skews[2] = {"txen-skew-ps", "rxdv-skew-ps"};
        const struct device *dev_walker;
+       int result;
+
+       result = ksz9031_enable_edpd(phydev);
+       if (result < 0)
+               return result;
 
        /* The Micrel driver has a deprecated option to place phy OF
         * properties in the MAC node. Walk up the tree of devices to
-- 
1.9.1