net: phy: realtek: add interrupt support for RTL8221B

This commit introduces interrupt support for RTL8221B (C45 mode).
Interrupts are mapped on the VEND2 page. VEND2 registers are only
accessible via C45 reads and cannot be accessed by C45 over C22.

Signed-off-by: Jianhui Zhao <[e-mail]>
[Enable only link state change interrupts]
Signed-off-by: Aleksander Jan Bajkowski <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/realtek/realtek_main.c

···
  */
 #define RTL822X_VND2_C22_REG(reg)		(0xa400 + 2 * (reg))
 
+#define RTL8221B_VND2_INER			0xa4d2
+#define RTL8221B_VND2_INER_LINK_STATUS		BIT(4)
+
+#define RTL8221B_VND2_INSR			0xa4d4
+
 #define RTL8224_MII_RTCT			0x11
 #define RTL8224_MII_RTCT_ENABLE			BIT(0)
 #define RTL8224_MII_RTCT_PAIR_A			BIT(4)
···
 	return IRQ_HANDLED;
 }
 
+static int rtl8221b_ack_interrupt(struct phy_device *phydev)
+{
+	int err;
+
+	err = phy_read_mmd(phydev, MDIO_MMD_VEND2, RTL8221B_VND2_INSR);
+
+	return (err < 0) ? err : 0;
+}
+
+static int rtl8221b_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = rtl8221b_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write_mmd(phydev, MDIO_MMD_VEND2, RTL8221B_VND2_INER,
+				    RTL8221B_VND2_INER_LINK_STATUS);
+	} else {
+		err = phy_write_mmd(phydev, MDIO_MMD_VEND2,
+				    RTL8221B_VND2_INER, 0);
+		if (err)
+			return err;
+
+		err = rtl8221b_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t rtl8221b_handle_interrupt(struct phy_device *phydev)
+{
+	int err;
+
+	err = rtl8221b_ack_interrupt(phydev);
+	if (err) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
 static struct phy_driver realtek_drvs[] = {
 	{
 		PHY_ID_MATCH_EXACT(0x00008201),
···
 	}, {
 		.match_phy_device = rtl8221b_vb_cg_c45_match_phy_device,
 		.name           = "RTL8221B-VB-CG 2.5Gbps PHY (C45)",
+		.config_intr	= rtl8221b_config_intr,
+		.handle_interrupt = rtl8221b_handle_interrupt,
 		.probe		= rtl822x_probe,
 		.config_init    = rtl822xb_config_init,
 		.get_rate_matching = rtl822xb_get_rate_matching,
···
 	}, {
 		.match_phy_device = rtl8221b_vm_cg_c45_match_phy_device,
 		.name           = "RTL8221B-VM-CG 2.5Gbps PHY (C45)",
+		.config_intr	= rtl8221b_config_intr,
+		.handle_interrupt = rtl8221b_handle_interrupt,
 		.probe		= rtl822x_probe,
 		.config_init    = rtl822xb_config_init,
 		.get_rate_matching = rtl822xb_get_rate_matching,