[PATCH 2/6] rtc: sun6i: Add some locking

[Maxime Ripard]

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

Add some locking to prevent from concurrent accesses.

Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
---
 drivers/rtc/rtc-sun6i.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
index 408dd512a6ac..872d18609183 100644
--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -125,6 +125,8 @@ struct sun6i_rtc_dev {
 	struct clk_hw hw;
 	struct clk_hw *int_osc;
 	struct clk *losc;
+
+	spinlock_t lock;
 };
 
 static struct sun6i_rtc_dev *sun6i_rtc;
@@ -155,16 +157,19 @@ static u8 sun6i_rtc_osc_get_parent(struct clk_hw *hw)
 static int sun6i_rtc_osc_set_parent(struct clk_hw *hw, u8 index)
 {
 	struct sun6i_rtc_dev *rtc = container_of(hw, struct sun6i_rtc_dev, hw);
+	unsigned long flags;
 	u32 val;
 
 	if (index > 1)
 		return -EINVAL;
 
+	spin_lock_irqsave(&rtc->lock, flags);
 	val = readl(rtc->base + SUN6I_LOSC_CTRL);
 	val &= ~SUN6I_LOSC_CTRL_EXT_OSC;
 	val |= SUN6I_LOSC_CTRL_KEY;
 	val |= index ? SUN6I_LOSC_CTRL_EXT_OSC : 0;
 	writel(val, rtc->base + SUN6I_LOSC_CTRL);
+	spin_unlock_irqrestore(&rtc->lock, flags);
 
 	return 0;
 }
@@ -187,6 +192,7 @@ static void __init sun6i_rtc_clk_init(struct device_node *node)
 	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
 	if (!rtc)
 		pr_crit("Can't allocate RTC structure\n");
+	spin_lock_init(&rtc->lock);
 
 	rtc->base = of_io_request_and_map(node, 0, of_node_full_name(node));
 	if (!rtc->base) {
@@ -246,8 +252,10 @@ CLK_OF_DECLARE_DRIVER(sun6i_rtc_clk, "allwinner,sun6i-a31-rtc",
 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) {
@@ -256,10 +264,11 @@ static irqreturn_t sun6i_rtc_alarmirq(int irq, void *id)
 
 		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)
@@ -267,6 +276,7 @@ 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;
@@ -277,9 +287,11 @@ static void sun6i_rtc_setaie(int to, struct sun6i_rtc_dev *chip)
 		       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)
@@ -318,11 +330,15 @@ 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);
-- 
git-series 0.8.11