[PATCH] rtc: rtc-at91rm9200: fix infinite wait for ACKUPD irq

[Boris BREZILLON]

The rtc user must wait at least 1 sec between each time/calandar update
(see atmel's datasheet chapter "Updating Time/Calendar").

Use the 1Hz interrupt to update the at91_rtc_upd_rdy flag and wait for
the at91_rtc_wait_upd_rdy event if the rtc is not ready.

Signed-off-by: Boris BREZILLON <boris.brezillon at free-electrons.com>
Reported-by: Bryan Evenson <bevenson at melinkcorp.com>
---
Hello Bryan,

I reproduced your bug (using your script) and this patch seems to fix the
problem.

Could you try it and let me know if it works for you ?

Best Regards,

Boris

 drivers/rtc/rtc-at91rm9200.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
index 3281c90..e3fe54c 100644
--- a/drivers/rtc/rtc-at91rm9200.c
+++ b/drivers/rtc/rtc-at91rm9200.c
@@ -48,11 +48,13 @@ struct at91_rtc_config {
 
 static const struct at91_rtc_config *at91_rtc_config;
 static DECLARE_COMPLETION(at91_rtc_updated);
+static DECLARE_COMPLETION(at91_rtc_wait_upd_rdy);
 static unsigned int at91_alarm_year = AT91_RTC_EPOCH;
 static void __iomem *at91_rtc_regs;
 static int irq;
 static DEFINE_SPINLOCK(at91_rtc_lock);
 static u32 at91_rtc_shadow_imr;
+static bool at91_rtc_upd_rdy;
 
 static void at91_rtc_write_ier(u32 mask)
 {
@@ -161,6 +163,8 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
 		1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
 		tm->tm_hour, tm->tm_min, tm->tm_sec);
 
+	wait_for_completion(&at91_rtc_wait_upd_rdy);
+
 	/* Stop Time/Calendar from counting */
 	cr = at91_rtc_read(AT91_RTC_CR);
 	at91_rtc_write(AT91_RTC_CR, cr | AT91_RTC_UPDCAL | AT91_RTC_UPDTIM);
@@ -183,6 +187,7 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
 
 	/* Restart Time/Calendar */
 	cr = at91_rtc_read(AT91_RTC_CR);
+	at91_rtc_upd_rdy = 0;
 	at91_rtc_write(AT91_RTC_CR, cr & ~(AT91_RTC_UPDCAL | AT91_RTC_UPDTIM));
 
 	return 0;
@@ -290,8 +295,13 @@ static irqreturn_t at91_rtc_interrupt(int irq, void *dev_id)
 	if (rtsr) {		/* this interrupt is shared!  Is it ours? */
 		if (rtsr & AT91_RTC_ALARM)
 			events |= (RTC_AF | RTC_IRQF);
-		if (rtsr & AT91_RTC_SECEV)
+		if (rtsr & AT91_RTC_SECEV) {
 			events |= (RTC_UF | RTC_IRQF);
+			if (!at91_rtc_upd_rdy) {
+				at91_rtc_upd_rdy = 1;
+				complete(&at91_rtc_wait_upd_rdy);
+			}
+		}
 		if (rtsr & AT91_RTC_ACKUPD)
 			complete(&at91_rtc_updated);
 
@@ -413,6 +423,8 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
 		return PTR_ERR(rtc);
 	platform_set_drvdata(pdev, rtc);
 
+	/* Enable 1Hz events */
+	at91_rtc_write_ier(AT91_RTC_SECEV);
 	dev_info(&pdev->dev, "AT91 Real Time Clock driver.\n");
 	return 0;
 }
-- 
1.8.3.2