Add locking to `vf610_gpio_direction_input|output()` functions. Without this locking, a race condition exists between concurrent calls to these functions, potentially leading to incorrect GPIO direction settings.
To verify the correctness of this fix, a `trylock` patch was applied, where after a couple of reboots the race was confirmed. I.e., one user had to wait before acquiring the lock. With this patch the race has not been encountered. It's worth mentioning that any type of debugging (printing, tracing, etc.) would "resolve"/hide the issue.
Fixes: 659d8a62311f ("gpio: vf610: add imx7ulp support") Signed-off-by: Johan Korsnes johan.korsnes@remarkable.no Reviewed-by: Linus Walleij linus.walleij@linaro.org Reviewed-by: Haibo Chen haibo.chen@nxp.com Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: stable@vger.kernel.org
---
v3 - Use guards from cleanup.h for spinlock - Added linux-stable to cc - Added Fixes: tags
v2 - Added description on correcctness to commit text - Added Reviewed-by from Walleij and Haibo --- drivers/gpio/gpio-vf610.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpio/gpio-vf610.c b/drivers/gpio/gpio-vf610.c index c4f34a347cb6..c36a9dbccd4d 100644 --- a/drivers/gpio/gpio-vf610.c +++ b/drivers/gpio/gpio-vf610.c @@ -36,6 +36,7 @@ struct vf610_gpio_port { struct clk *clk_port; struct clk *clk_gpio; int irq; + spinlock_t lock; /* protect gpio direction registers */ };
#define GPIO_PDOR 0x00 @@ -124,6 +125,7 @@ static int vf610_gpio_direction_input(struct gpio_chip *chip, unsigned int gpio) u32 val;
if (port->sdata->have_paddr) { + guard(spinlock_irqsave)(&port->lock); val = vf610_gpio_readl(port->gpio_base + GPIO_PDDR); val &= ~mask; vf610_gpio_writel(val, port->gpio_base + GPIO_PDDR); @@ -142,6 +144,7 @@ static int vf610_gpio_direction_output(struct gpio_chip *chip, unsigned int gpio vf610_gpio_set(chip, gpio, value);
if (port->sdata->have_paddr) { + guard(spinlock_irqsave)(&port->lock); val = vf610_gpio_readl(port->gpio_base + GPIO_PDDR); val |= mask; vf610_gpio_writel(val, port->gpio_base + GPIO_PDDR); @@ -297,6 +300,7 @@ static int vf610_gpio_probe(struct platform_device *pdev) return -ENOMEM;
port->sdata = device_get_match_data(dev); + spin_lock_init(&port->lock);
dual_base = port->sdata->have_dual_base;