[PATCH v4 4/9] rtc: abx80x: properly handle shared IRQs

The abx80x RTC driver registers its interrupt handler with IRQF_SHARED,
but the handler always returned IRQ_HANDLED and cleared the status
register even when no interrupt source from the RTC was active.

This could cause the driver to claim interrupts belonging to other
devices sharing the same IRQ line and could also clear unrelated status
bits in the RTC status register.

Only handle the interrupt when the alarm or watchdog flags are set, and
clear only those interrupt status bits that were handled. Return
IRQ_NONE when the interrupt was not generated by the RTC.

Fixes: 718a820a303c ("rtc: abx80x: add alarm support")
Signed-off-by: Antoni Pokusinski <[email protected]>
---
 drivers/rtc/rtc-abx80x.c | 54 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
index 0c8d3416fd5a..485d1ea08030 100644
--- a/drivers/rtc/rtc-abx80x.c
+++ b/drivers/rtc/rtc-abx80x.c
@@ -51,12 +51,18 @@
 #define ABX8XX_CTRL2_RSVD	BIT(5)
 
 #define ABX8XX_REG_IRQ		0x12
+#define ABX8XX_IRQ_EX1E		BIT(0)
+#define ABX8XX_IRQ_EX2E		BIT(1)
 #define ABX8XX_IRQ_AIE		BIT(2)
+#define ABX8XX_IRQ_TIE		BIT(3)
+#define ABX8XX_IRQ_BLIE		BIT(4)
 #define ABX8XX_IRQ_IM_1_4	(0x3 << 5)
 
 #define ABX8XX_REG_CD_TIMER_CTL	0x18
 
 #define ABX8XX_REG_OSC		0x1c
+#define ABX8XX_OSC_ACIE		BIT(0)
+#define ABX8XX_OSC_OFIE		BIT(1)
 #define ABX8XX_OSC_FOS		BIT(3)
 #define ABX8XX_OSC_BOS		BIT(4)
 #define ABX8XX_OSC_ACAL_512	BIT(5)
@@ -266,27 +272,34 @@ static irqreturn_t abx80x_handle_irq(int irq, void *dev_id)
 	struct i2c_client *client = dev_id;
 	struct abx80x_priv *priv = i2c_get_clientdata(client);
 	struct rtc_device *rtc = priv->rtc;
+	irqreturn_t handled = IRQ_NONE;
 	int status;
 
 	guard(mutex)(&priv->lock);
 
 	status = i2c_smbus_read_byte_data(client, ABX8XX_REG_STATUS);
 	if (status < 0)
-		return IRQ_NONE;
+		return handled;
 
-	if (status & ABX8XX_STATUS_AF)
+	if (status & ABX8XX_STATUS_AF) {
 		rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF);
+		handled = IRQ_HANDLED;
+	}
 
 	/*
 	 * It is unclear if we'll get an interrupt before the external
 	 * reset kicks in.
 	 */
-	if (status & ABX8XX_STATUS_WDT)
+	if (status & ABX8XX_STATUS_WDT) {
 		dev_alert(&client->dev, "watchdog timeout interrupt.\n");
+		handled = IRQ_HANDLED;
+	}
 
-	i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS, 0);
+	if (handled == IRQ_HANDLED)
+		i2c_smbus_write_byte_data(client, ABX8XX_REG_STATUS,
+					  status & ~(ABX8XX_STATUS_AF | ABX8XX_STATUS_WDT));
 
-	return IRQ_HANDLED;
+	return handled;
 }
 
 static int abx80x_read_alarm(struct device *dev, struct rtc_wkalrm *t)
@@ -950,6 +963,37 @@ static int abx80x_probe(struct i2c_client *client)
 	if (err)
 		return err;
 
+	/* Disable unused interrupts */
+	data = i2c_smbus_read_byte_data(client, ABX8XX_REG_IRQ);
+	if (data < 0) {
+		dev_err(&client->dev, "Unable to read irq register\n");
+		return -EIO;
+	}
+
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_IRQ,
+					data & ~(ABX8XX_IRQ_EX1E |
+						 ABX8XX_IRQ_EX2E |
+						 ABX8XX_IRQ_TIE |
+						 ABX8XX_IRQ_BLIE));
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write irq register\n");
+		return -EIO;
+	}
+
+	data = i2c_smbus_read_byte_data(client, ABX8XX_REG_OSC);
+	if (data < 0) {
+		dev_err(&client->dev, "Unable to read Oscillator Control register\n");
+		return -EIO;
+	}
+
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_OSC,
+					data & ~(ABX8XX_OSC_ACIE |
+						 ABX8XX_OSC_OFIE));
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write Oscillator Control register\n");
+		return -EIO;
+	}
+
 	if (client->irq > 0) {
 		dev_info(&client->dev, "IRQ %d supplied\n", client->irq);
 		err = devm_request_threaded_irq(&client->dev, client->irq, NULL,
-- 
2.55.0