From: Boris BREZILLON <boris.brezillon@xxxxxxxxxxxxxxxxxx>
Subject: rtc: rtc-at91rm9200: fix infinite wait for ACKUPD irq
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.
This patch fixes a deadlock in an uninterruptible wait when the RTC is
updated more than once every second. AFAICT the bug is here from the
beginning, but I think we should at least backport this fix to 3.10 and
the following longterm and stable releases.
Signed-off-by: Boris BREZILLON <boris.brezillon@xxxxxxxxxxxxxxxxxx>
Reported-by: Bryan Evenson <bevenson@xxxxxxxxxxxxxx>
Tested-by: Bryan Evenson <bevenson@xxxxxxxxxxxxxx>
Cc: Andrew Victor <linux@xxxxxxxxxxxx>
Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx>
Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/rtc/rtc-at91rm9200.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff -puN drivers/rtc/rtc-at91rm9200.c~rtc-rtc-at91rm9200-fix-infinite-wait-for-ackupd-irq drivers/rtc/rtc-at91rm9200.c
--- a/drivers/rtc/rtc-at91rm9200.c~rtc-rtc-at91rm9200-fix-infinite-wait-for-ackupd-irq
+++ a/drivers/rtc/rtc-at91rm9200.c
@@ -48,6 +48,7 @@ struct at91_rtc_config {
static const struct at91_rtc_config *at91_rtc_config;
static DECLARE_COMPLETION(at91_rtc_updated);
+static DECLARE_COMPLETION(at91_rtc_upd_rdy);
static unsigned int at91_alarm_year = AT91_RTC_EPOCH;
static void __iomem *at91_rtc_regs;
static int irq;
@@ -161,6 +162,8 @@ static int at91_rtc_settime(struct devic
1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
tm->tm_hour, tm->tm_min, tm->tm_sec);
+ wait_for_completion(&at91_rtc_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);
@@ -183,7 +186,9 @@ static int at91_rtc_settime(struct devic
/* Restart Time/Calendar */
cr = at91_rtc_read(AT91_RTC_CR);
+ at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_SECEV);
at91_rtc_write(AT91_RTC_CR, cr & ~(AT91_RTC_UPDCAL | AT91_RTC_UPDTIM));
+ at91_rtc_write_ier(AT91_RTC_SECEV);
return 0;
}
@@ -290,8 +295,10 @@ static irqreturn_t at91_rtc_interrupt(in
if (rtsr) { /* this interrupt is shared! Is it ours? */
if (rtsr & AT91_RTC_ALARM)
events |= (RTC_AF | RTC_IRQF);
- if (rtsr & AT91_RTC_SECEV)
- events |= (RTC_UF | RTC_IRQF);
+ if (rtsr & AT91_RTC_SECEV) {
+ complete(&at91_rtc_upd_rdy);
+ at91_rtc_write_idr(AT91_RTC_SECEV);
+ }
if (rtsr & AT91_RTC_ACKUPD)
complete(&at91_rtc_updated);
@@ -413,6 +420,11 @@ static int __init at91_rtc_probe(struct
return PTR_ERR(rtc);
platform_set_drvdata(pdev, rtc);
+ /* enable SECEV interrupt in order to initialize at91_rtc_upd_rdy
+ * completion.
+ */
+ at91_rtc_write_ier(AT91_RTC_SECEV);
+
dev_info(&pdev->dev, "AT91 Real Time Clock driver.\n");
return 0;
}
_
--
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