gpio: vf610: add locking to gpio direction functions

BugLink: https://bugs.launchpad.net/bugs/2107437

[ Upstream commit 4e667a1 ]

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: 659d8a6 ("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
Link: https://lore.kernel.org/r/20250217091643.679644-1-johan.korsnes@remarkable.no
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: johankor

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 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 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);
@@ -284,6 +287,7 @@ 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;