gpio: amd-fch: ionly return allowed values from amd_fch_gpio_get()

As of 86ef402 ("gpiolib: sanitize the return value of
gpio_chip::get()") gpiolib requires drivers implementing GPIOs to only
return 0, 1 or negative error for the get() callbacks. Ensure that
amd-fch complies with this requirement.

Fixes: 86ef402 ("gpiolib: sanitize the return value of gpio_chip::get()")
Reported-and-tested-by: Tj <tj.iam.tj@proton.me>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://patch.msgid.link/aZTlwnvHt2Gho4yN@google.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Author: dtor

drivers/gpio/gpio-amd-fch.c

@@ -8,6 +8,7 @@
  *
  */
 
+#include <linux/bitfield.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -120,15 +121,15 @@ static int amd_fch_gpio_get(struct gpio_chip *gc,
 			    unsigned int offset)
 {
 	unsigned long flags;
-	int ret;
+	u32 val;
 	struct amd_fch_gpio_priv *priv = gpiochip_get_data(gc);
 	void __iomem *ptr = amd_fch_gpio_addr(priv, offset);
 
 	spin_lock_irqsave(&priv->lock, flags);
-	ret = (readl_relaxed(ptr) & AMD_FCH_GPIO_FLAG_READ);
+	val = readl_relaxed(ptr);
 	spin_unlock_irqrestore(&priv->lock, flags);
 
-	return ret;
+	return FIELD_GET(AMD_FCH_GPIO_FLAG_READ, val);
 }
 
 static int amd_fch_gpio_request(struct gpio_chip *chip,