| From 489405fe5ed38e65f6f82f131a39c67f3bae6045 Mon Sep 17 00:00:00 2001 |
| From: Gregory CLEMENT <gregory.clement@free-electrons.com> |
| Date: Tue, 5 May 2015 16:24:05 -0700 |
| Subject: rtc: armada38x: fix concurrency access in armada38x_rtc_set_time |
| |
| From: Gregory CLEMENT <gregory.clement@free-electrons.com> |
| |
| commit 489405fe5ed38e65f6f82f131a39c67f3bae6045 upstream. |
| |
| 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> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| 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); |