[RFC PATCH net-next 1/8] net: phy: realtek: rtl8221: allow to configure SERDES mode

[Daniel Golle]

From: Alexander Couzens <lynxis@xxxxxxx>

The rtl8221 supports multiple SERDES modes:
- SGMII
- 2500base-x
- HiSGMII

Further it supports rate adaption on SERDES links to allow
slow ethernet speeds (10/100/1000mbit) to work on 2500base-x/HiSGMII
links without reducing the SERDES speed.

When operating without rate adapters the SERDES link will follow the
ethernet speed.

Signed-off-by: Alexander Couzens <lynxis@xxxxxxx>
---
 drivers/net/phy/realtek.c | 53 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index 3d99fd6664d7a..6389abaab6d5a 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -53,6 +53,15 @@
 						 RTL8201F_ISR_LINK)
 #define RTL8201F_IER				0x13
 
+#define RTL8221B_MMD_SERDES_CTRL		MDIO_MMD_VEND1
+#define RTL8221B_MMD_PHY_CTRL			MDIO_MMD_VEND2
+#define RTL8221B_SERDES_OPTION			0x697a
+#define RTL8221B_SERDES_OPTION_MODE_MASK	GENMASK(5, 0)
+#define RTL8221B_SERDES_OPTION_MODE_2500BASEX_SGMII	0
+#define RTL8221B_SERDES_OPTION_MODE_HISGMII_SGMII	1
+#define RTL8221B_SERDES_OPTION_MODE_2500BASEX		2
+#define RTL8221B_SERDES_OPTION_MODE_HISGMII		3
+
 #define RTL8366RB_POWER_SAVE			0x15
 #define RTL8366RB_POWER_SAVE_ON			BIT(12)
 
@@ -849,6 +858,48 @@ static irqreturn_t rtl9000a_handle_interrupt(struct phy_device *phydev)
 	return IRQ_HANDLED;
 }
 
+static int rtl8221b_config_init(struct phy_device *phydev)
+{
+	u16 option_mode;
+
+	switch (phydev->interface) {
+	case PHY_INTERFACE_MODE_2500BASEX:
+		if (!phydev->is_c45) {
+			option_mode = RTL8221B_SERDES_OPTION_MODE_2500BASEX;
+			break;
+		}
+		fallthrough;
+	case PHY_INTERFACE_MODE_SGMII:
+		option_mode = RTL8221B_SERDES_OPTION_MODE_2500BASEX_SGMII;
+		break;
+	default:
+		return 0;
+	}
+
+	phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL,
+		      0x75f3, 0);
+
+	phy_modify_mmd_changed(phydev, RTL8221B_MMD_SERDES_CTRL,
+			       RTL8221B_SERDES_OPTION,
+			       RTL8221B_SERDES_OPTION_MODE_MASK, option_mode);
+	switch (option_mode) {
+	case RTL8221B_SERDES_OPTION_MODE_2500BASEX_SGMII:
+	case RTL8221B_SERDES_OPTION_MODE_2500BASEX:
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6a04, 0x0503);
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6f10, 0xd455);
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6f11, 0x8020);
+		break;
+	case RTL8221B_SERDES_OPTION_MODE_HISGMII_SGMII:
+	case RTL8221B_SERDES_OPTION_MODE_HISGMII:
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6a04, 0x0503);
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6f10, 0xd433);
+		phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x6f11, 0x8020);
+		break;
+	}
+
+	return 0;
+}
+
 static struct phy_driver realtek_drvs[] = {
 	{
 		PHY_ID_MATCH_EXACT(0x00008201),
@@ -1001,6 +1052,7 @@ static struct phy_driver realtek_drvs[] = {
 		PHY_ID_MATCH_EXACT(0x001cc849),
 		.name           = "RTL8221B-VB-CG 2.5Gbps PHY",
 		.get_features   = rtl822x_get_features,
+		.config_init    = rtl8221b_config_init,
 		.config_aneg    = rtl822x_config_aneg,
 		.read_status    = rtl822x_read_status,
 		.suspend        = genphy_suspend,
@@ -1012,6 +1064,7 @@ static struct phy_driver realtek_drvs[] = {
 		.name           = "RTL8221B-VM-CG 2.5Gbps PHY",
 		.get_features   = rtl822x_get_features,
 		.config_aneg    = rtl822x_config_aneg,
+		.config_init    = rtl8221b_config_init,
 		.read_status    = rtl822x_read_status,
 		.suspend        = genphy_suspend,
 		.resume         = rtlgen_resume,
-- 
2.40.0