[PATCH] net: phy: adin1100: Fix nullptr exception for phy interrupts

[Andre Werner <andre.werner@systec-electronic.com>]

If using ADIN1100 as an external phy, e.g. in combination with
"smsc95xx", we ran into nullptr exception by creating a link.

In our case the "smsc95xx" does not check for an available interrupt handler
on external phy driver to use poll instead of interrupts if no handler is
available. So we decide to implement a small handler in the phy driver
to support other MACs as well.

I update the driver to add an interrupt handler because libphy
does not check if their is a interrupt handler available either.

There are several interrupts maskable at the phy, but only link change interrupts
are handled by the driver yet.

We tested the combination "smsc95xx" and "adin1100" with Linux Kernel 6.6.9
and Linux Kernel 6.1.0, respectively.

Signed-off-by: Andre Werner <andre.werner@systec-electronic.com>
---
 drivers/net/phy/adin1100.c | 58 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/net/phy/adin1100.c b/drivers/net/phy/adin1100.c
index 7619d6185801..ed8a7e6250cf 100644
--- a/drivers/net/phy/adin1100.c
+++ b/drivers/net/phy/adin1100.c
@@ -18,6 +18,12 @@
 #define PHY_ID_ADIN1110				0x0283bc91
 #define PHY_ID_ADIN2111				0x0283bca1
 
+#define ADIN_PHY_SUBSYS_IRQ_MASK		0x0021
+#define   ADIN_LINK_STAT_CHNG_IRQ_EN		BIT(1)
+
+#define ADIN_PHY_SUBSYS_IRQ_STATUS		0x0011
+#define   ADIN_LINK_STAT_CHNG			BIT(1)
+
 #define ADIN_FORCED_MODE			0x8000
 #define   ADIN_FORCED_MODE_EN			BIT(0)
 
@@ -136,6 +142,56 @@ static int adin_config_aneg(struct phy_device *phydev)
 	return genphy_c45_config_aneg(phydev);
 }
 
+static int adin_phy_ack_intr(struct phy_device *phydev)
+{
+	/* Clear pending interrupts */
+	int rc = phy_read_mmd(phydev, MDIO_MMD_VEND2, ADIN_PHY_SUBSYS_IRQ_STATUS);
+
+	return rc < 0 ? rc : 0;
+}
+
+static int adin_config_intr(struct phy_device *phydev)
+{
+	int ret, regval;
+
+	ret = adin_phy_ack_intr(phydev);
+
+	if (ret)
+		return ret;
+
+	regval = phy_read_mmd(phydev, MDIO_MMD_VEND2, ADIN_PHY_SUBSYS_IRQ_MASK);
+	if (regval < 0)
+		return regval;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED)
+		regval |= ADIN_LINK_STAT_CHNG_IRQ_EN;
+	else
+		regval &= ~ADIN_LINK_STAT_CHNG_IRQ_EN;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_VEND2,
+			    ADIN_PHY_SUBSYS_IRQ_MASK,
+			    regval);
+	return ret;
+}
+
+static irqreturn_t adin_phy_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read_mmd(phydev, MDIO_MMD_VEND2, ADIN_PHY_SUBSYS_IRQ_STATUS);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & ADIN_LINK_STAT_CHNG))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
 static int adin_set_powerdown_mode(struct phy_device *phydev, bool en)
 {
 	int ret;
@@ -275,6 +331,8 @@ static struct phy_driver adin_driver[] = {
 		.probe			= adin_probe,
 		.config_aneg		= adin_config_aneg,
 		.read_status		= adin_read_status,
+		.config_intr		= adin_config_intr,
+		.handle_interrupt	= adin_phy_handle_interrupt,
 		.set_loopback		= adin_set_loopback,
 		.suspend		= adin_suspend,
 		.resume			= adin_resume,
-- 
2.43.0