[PATCH 4.4 83/91] rtc: sun6i: Add some locking

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maxime Ripard <maxime.rip...@free-electrons.com>

commit a9422a19ce270a22fc520f2278fb7e80c58be508 upstream.

Some registers have a read-modify-write access pattern that are not atomic.

Add some locking to prevent from concurrent accesses.

Acked-by: Chen-Yu Tsai <w...@csie.org>
Signed-off-by: Maxime Ripard <maxime.rip...@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.bell...@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/rtc/rtc-sun6i.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -114,13 +114,17 @@ struct sun6i_rtc_dev {
        void __iomem *base;
        int irq;
        unsigned long alarm;
+
+       spinlock_t lock;
 };
 
 static irqreturn_t sun6i_rtc_alarmirq(int irq, void *id)
 {
        struct sun6i_rtc_dev *chip = (struct sun6i_rtc_dev *) id;
+       irqreturn_t ret = IRQ_NONE;
        u32 val;
 
+       spin_lock(&chip->lock);
        val = readl(chip->base + SUN6I_ALRM_IRQ_STA);
 
        if (val & SUN6I_ALRM_IRQ_STA_CNT_IRQ_PEND) {
@@ -129,10 +133,11 @@ static irqreturn_t sun6i_rtc_alarmirq(in
 
                rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);
 
-               return IRQ_HANDLED;
+               ret = IRQ_HANDLED;
        }
+       spin_unlock(&chip->lock);
 
-       return IRQ_NONE;
+       return ret;
 }
 
 static void sun6i_rtc_setaie(int to, struct sun6i_rtc_dev *chip)
@@ -140,6 +145,7 @@ static void sun6i_rtc_setaie(int to, str
        u32 alrm_val = 0;
        u32 alrm_irq_val = 0;
        u32 alrm_wake_val = 0;
+       unsigned long flags;
 
        if (to) {
                alrm_val = SUN6I_ALRM_EN_CNT_EN;
@@ -150,9 +156,11 @@ static void sun6i_rtc_setaie(int to, str
                       chip->base + SUN6I_ALRM_IRQ_STA);
        }
 
+       spin_lock_irqsave(&chip->lock, flags);
        writel(alrm_val, chip->base + SUN6I_ALRM_EN);
        writel(alrm_irq_val, chip->base + SUN6I_ALRM_IRQ_EN);
        writel(alrm_wake_val, chip->base + SUN6I_ALARM_CONFIG);
+       spin_unlock_irqrestore(&chip->lock, flags);
 }
 
 static int sun6i_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
@@ -191,11 +199,15 @@ static int sun6i_rtc_gettime(struct devi
 static int sun6i_rtc_getalarm(struct device *dev, struct rtc_wkalrm *wkalrm)
 {
        struct sun6i_rtc_dev *chip = dev_get_drvdata(dev);
+       unsigned long flags;
        u32 alrm_st;
        u32 alrm_en;
 
+       spin_lock_irqsave(&chip->lock, flags);
        alrm_en = readl(chip->base + SUN6I_ALRM_IRQ_EN);
        alrm_st = readl(chip->base + SUN6I_ALRM_IRQ_STA);
+       spin_unlock_irqrestore(&chip->lock, flags);
+
        wkalrm->enabled = !!(alrm_en & SUN6I_ALRM_EN_CNT_EN);
        wkalrm->pending = !!(alrm_st & SUN6I_ALRM_EN_CNT_EN);
        rtc_time_to_tm(chip->alarm, &wkalrm->time);
@@ -356,6 +368,7 @@ static int sun6i_rtc_probe(struct platfo
        chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
        if (!chip)
                return -ENOMEM;
+       spin_lock_init(&chip->lock);
 
        platform_set_drvdata(pdev, chip);
        chip->dev = &pdev->dev;