rtc: sun6i: Add some locking

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

Add some locking to prevent from concurrent accesses.

Cc: [e-mail]
Acked-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/rtc-sun6i.c

···
 	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) {
···
 
 		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)
···
 	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;
···
 		       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)
···
 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);
···
 	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;