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authorGregory CLEMENT <gregory.clement@free-electrons.com>2015-05-05 16:24:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-05-05 17:10:11 -0700
commit489405fe5ed38e65f6f82f131a39c67f3bae6045 (patch)
treedb6e2324ac636c6421c7186b898913045f53eaf2 /drivers/rtc
parentb1432a2a35565f538586774a03bf277c27fc267d (diff)
downloadlinux-489405fe5ed38e65f6f82f131a39c67f3bae6045.tar.bz2
rtc: armada38x: fix concurrency access in armada38x_rtc_set_time
While setting the time, the RTC TIME register should not be accessed. However due to hardware constraints, setting the RTC time involves sleeping during 100ms. This sleep was done outside the critical section protected by the spinlock, so it was possible to read the RTC TIME register and get an incorrect value. This patch introduces a mutex for protecting the RTC TIME access, unlike the spinlock it is allowed to sleep in a critical section protected by a mutex. The RTC STATUS register can still be used from the interrupt handler but it has no effect on setting the time. Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Acked-by: Andrew Lunn <andrew@lunn.ch> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: <stable@vger.kernel.org> [4.0] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/rtc')
-rw-r--r--drivers/rtc/rtc-armada38x.c24
1 files changed, 12 insertions, 12 deletions
diff --git a/drivers/rtc/rtc-armada38x.c b/drivers/rtc/rtc-armada38x.c
index 43e04af39e09..cb70ced7e0db 100644
--- a/drivers/rtc/rtc-armada38x.c
+++ b/drivers/rtc/rtc-armada38x.c
@@ -40,6 +40,13 @@ struct armada38x_rtc {
void __iomem *regs;
void __iomem *regs_soc;
spinlock_t lock;
+ /*
+ * While setting the time, the RTC TIME register should not be
+ * accessed. Setting the RTC time involves sleeping during
+ * 100ms, so a mutex instead of a spinlock is used to protect
+ * it
+ */
+ struct mutex mutex_time;
int irq;
};
@@ -59,8 +66,7 @@ static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm)
struct armada38x_rtc *rtc = dev_get_drvdata(dev);
unsigned long time, time_check, flags;
- spin_lock_irqsave(&rtc->lock, flags);
-
+ mutex_lock(&rtc->mutex_time);
time = readl(rtc->regs + RTC_TIME);
/*
* WA for failing time set attempts. As stated in HW ERRATA if
@@ -71,7 +77,7 @@ static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm)
if ((time_check - time) > 1)
time_check = readl(rtc->regs + RTC_TIME);
- spin_unlock_irqrestore(&rtc->lock, flags);
+ mutex_unlock(&rtc->mutex_time);
rtc_time_to_tm(time_check, tm);
@@ -94,19 +100,12 @@ static int armada38x_rtc_set_time(struct device *dev, struct rtc_time *tm)
* then wait for 100ms before writing to the time register to be
* sure that the data will be taken into account.
*/
- spin_lock_irqsave(&rtc->lock, flags);
-
+ mutex_lock(&rtc->mutex_time);
rtc_delayed_write(0, rtc, RTC_STATUS);
-
- spin_unlock_irqrestore(&rtc->lock, flags);
-
msleep(100);
-
- spin_lock_irqsave(&rtc->lock, flags);
-
rtc_delayed_write(time, rtc, RTC_TIME);
+ mutex_unlock(&rtc->mutex_time);
- spin_unlock_irqrestore(&rtc->lock, flags);
out:
return ret;
}
@@ -230,6 +229,7 @@ static __init int armada38x_rtc_probe(struct platform_device *pdev)
return -ENOMEM;
spin_lock_init(&rtc->lock);
+ mutex_init(&rtc->mutex_time);
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "rtc");
rtc->regs = devm_ioremap_resource(&pdev->dev, res);