rtc: isl1208: Add a delay for clearing alarm

As per the latest HW manual[1], the INT# output is pulled low after the
alarm is triggered. After the INT# output is pulled low, it is low for at
least 250ms, even if the correct action is taken to clear it. It is
impossible to clear ALM if it is still active. The host must wait for the
RTC to progress past the alarm time plus the 250ms delay before clearing
ALM.

[1]https://www.renesas.com/us/en/document/dst/raa215300-datasheet?r=1506351

Signed-off-by: Biju Das <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexandre Belloni <[email protected]>

Author: bijudas

drivers/rtc/rtc-isl1208.c

@@ -7,6 +7,7 @@
 
 #include <linux/bcd.h>
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -628,6 +629,18 @@ isl1208_rtc_interrupt(int irq, void *data)
 	struct isl1208_state *isl1208 = i2c_get_clientdata(client);
 	int handled = 0, sr, err;
 
+	if (!isl1208->config->has_tamper) {
+		/*
+		 * The INT# output is pulled low 250ms after the alarm is
+		 * triggered. After the INT# output is pulled low, it is low for
+		 * at least 250ms, even if the correct action is taken to clear
+		 * it. It is impossible to clear ALM if it is still active. The
+		 * host must wait for the RTC to progress past the alarm time
+		 * plus the 250ms delay before clearing ALM.
+		 */
+		msleep(250);
+	}
+
 	/*
 	 * I2C reads get NAK'ed if we read straight away after an interrupt?
 	 * Using a mdelay/msleep didn't seem to help either, so we work around