[PATCH v6 4/4] net: phy: realtek: add RTL8224 polarity support

[Damien Dejean <dam.dejean@gmail.com>]

The RTL8224 has a register to configure the polarity of every pair of
each port. It provides device designers more flexbility when wiring the
chip.

Unfortunately, the register is left in an unknown state after a reset.
Thus on devices where the bootloader don't initialize it, the driver has
to do it to detect and use a link.

The MDI polarity swap can be set in the device tree using the property
enet-phy-pair-polarity. The u32 value is a bitfield where bit[0..3]
control the polarity of pairs A..D.

Signed-off-by: Damien Dejean <dam.dejean@gmail.com>
---
 drivers/net/phy/realtek/realtek_main.c | 45 +++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/realtek/realtek_main.c b/drivers/net/phy/realtek/realtek_main.c
index 4f0c1b72f7e0..d15d3b41e5d1 100644
--- a/drivers/net/phy/realtek/realtek_main.c
+++ b/drivers/net/phy/realtek/realtek_main.c
@@ -172,6 +172,7 @@
 #define RTL8224_SRAM_RTCT_LEN(pair)		(0x8028 + (pair) * 4)
 
 #define RTL8224_VND1_MDI_PAIR_SWAP		0xa90
+#define RTL8224_VND1_MDI_POLARITY_SWAP		0xa94
 
 #define RTL8366RB_POWER_SAVE			0x15
 #define RTL8366RB_POWER_SAVE_ON			BIT(12)
@@ -1861,9 +1862,51 @@ static int rtl8224_mdi_config_order(struct phy_device *phydev)
 	return ret;
 }
 
+static int rtl8224_mdi_config_polarity(struct phy_device *phydev)
+{
+	struct device_node *np = phydev->mdio.dev.of_node;
+	u8 offset = (phydev->mdio.addr & 3) * 4;
+	u32 polarity = 0;
+	int ret, val;
+
+	ret = of_property_read_u32(np, "enet-phy-pair-polarity", &polarity);
+
+	/* Do nothing if the property is not present */
+	if (ret == -EINVAL)
+		return 0;
+
+	if (ret)
+		return ret;
+
+	if (polarity & ~0xf)
+		return -EINVAL;
+
+	phy_lock_mdio_bus(phydev);
+	val = __phy_package_read_mmd(phydev, 0, MDIO_MMD_VEND1,
+				     RTL8224_VND1_MDI_POLARITY_SWAP);
+	if (val < 0) {
+		ret = val;
+		goto exit;
+	}
+
+	val &= ~(0xf << offset);
+	val |= polarity << offset;
+	ret = __phy_package_write_mmd(phydev, 0, MDIO_MMD_VEND1,
+				      RTL8224_VND1_MDI_POLARITY_SWAP, val);
+exit:
+	phy_unlock_mdio_bus(phydev);
+	return ret;
+}
+
 static int rtl8224_config_init(struct phy_device *phydev)
 {
-	return rtl8224_mdi_config_order(phydev);
+	int ret;
+
+	ret = rtl8224_mdi_config_order(phydev);
+	if (ret)
+		return ret;
+
+	return rtl8224_mdi_config_polarity(phydev);
 }
 
 static int rtl8224_probe(struct phy_device *phydev)
-- 
2.47.3