From: Gregory CLEMENT Date: Tue, 5 May 2015 23:24:05 +0000 (-0700) Subject: rtc: armada38x: fix concurrency access in armada38x_rtc_set_time X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=489405fe5ed38e65f6f82f131a39c67f3bae6045;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git 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 Acked-by: Alexandre Belloni Acked-by: Andrew Lunn Cc: Alessandro Zummo Cc: [4.0] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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);