[PATCH v2] rtc: zynqmp: Clear alarm interrupt status before interrupt enable

[Srinivas Neeli]

Fix multiple occurring interrupts for alarm interrupt. RTC module doesn't
clear the alarm interrupt status bit immediately after the interrupt is
triggered.This is due to the sticky nature of the alarm interrupt status
register. The alarm interrupt status register can be cleared only after
the second counter outruns the set alarm value. To fix multiple spurious
interrupts, disable alarm interrupt in the handler and clear the status
bit before enabling the alarm interrupt.

Fixes: 11143c19eb57 ("rtc: add xilinx zynqmp rtc driver")
Signed-off-by: Srinivas Neeli <srinivas.neeli@xxxxxxxxxx>
---
Changes in V2:
Addressed Michal Simek comments
 - Removed new line in declartion part.
 - Added new line before return.
---
 drivers/rtc/rtc-zynqmp.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index 5786866c09e9..4b1077e2f826 100644
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c
@@ -38,6 +38,8 @@
 
 #define RTC_CALIB_DEF		0x198233
 #define RTC_CALIB_MASK		0x1FFFFF
+#define RTC_ALRM_MASK          BIT(1)
+#define RTC_MSEC               1000
 
 struct xlnx_rtc_dev {
 	struct rtc_device	*rtc;
@@ -123,11 +125,28 @@ static int xlnx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 static int xlnx_rtc_alarm_irq_enable(struct device *dev, u32 enabled)
 {
 	struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
+	unsigned int status;
+	ulong timeout;
+
+	timeout = jiffies + msecs_to_jiffies(RTC_MSEC);
+
+	if (enabled) {
+		while (1) {
+			status = readl(xrtcdev->reg_base + RTC_INT_STS);
+			if (!((status & RTC_ALRM_MASK) == RTC_ALRM_MASK))
+				break;
+
+			if (time_after_eq(jiffies, timeout)) {
+				dev_err(dev, "Time out occur, while clearing alarm status bit\n");
+				return -ETIMEDOUT;
+			}
+			writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
+		}
 
-	if (enabled)
 		writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_EN);
-	else
+	} else {
 		writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_DIS);
+	}
 
 	return 0;
 }
@@ -183,8 +202,8 @@ static irqreturn_t xlnx_rtc_interrupt(int irq, void *id)
 	if (!(status & (RTC_INT_SEC | RTC_INT_ALRM)))
 		return IRQ_NONE;
 
-	/* Clear RTC_INT_ALRM interrupt only */
-	writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
+	/* Disable RTC_INT_ALRM interrupt only */
+	writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_DIS);
 
 	if (status & RTC_INT_ALRM)
 		rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_AF);
-- 
2.7.4