gpio: merrifield: Protect irq_ack() and gpio_set() by lock

There is a potential race when two threads do the writes to the same register
in parallel.

Prevent out of order in such case by protecting I/O access by spin lock.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-merrifield.c b/drivers/gpio/gpio-merrifield.c
index 11066f6..45b5127 100644 (file)
--- a/drivers/gpio/gpio-merrifield.c
+++ b/drivers/gpio/gpio-merrifield.c
@@ -105,7 +105,11 @@ static int mrfld_gpio_get(struct gpio_chip *chip, unsigned int offset)
 static void mrfld_gpio_set(struct gpio_chip *chip, unsigned int offset,
                           int value)
 {
+       struct mrfld_gpio *priv = gpiochip_get_data(chip);
        void __iomem *gpsr, *gpcr;
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&priv->lock, flags);
 
        if (value) {
                gpsr = gpio_reg(chip, offset, GPSR);
@@ -114,6 +118,8 @@ static void mrfld_gpio_set(struct gpio_chip *chip, unsigned int offset,
                gpcr = gpio_reg(chip, offset, GPCR);
                writel(BIT(offset % 32), gpcr);
        }
+
+       raw_spin_unlock_irqrestore(&priv->lock, flags);
 }
 
 static int mrfld_gpio_direction_input(struct gpio_chip *chip,
@@ -160,8 +166,13 @@ static void mrfld_irq_ack(struct irq_data *d)
        struct mrfld_gpio *priv = irq_data_get_irq_chip_data(d);
        u32 gpio = irqd_to_hwirq(d);
        void __iomem *gisr = gpio_reg(&priv->chip, gpio, GISR);
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&priv->lock, flags);
 
        writel(BIT(gpio % 32), gisr);
+
+       raw_spin_unlock_irqrestore(&priv->lock, flags);
 }
 
 static void mrfld_irq_unmask_mask(struct irq_data *d, bool unmask)