diff --git a/arch/avr32/mach-at32ap/pio.c b/arch/avr32/mach-at32ap/pio.c
index c3f596c..9ba5654 100644
--- a/arch/avr32/mach-at32ap/pio.c
+++ b/arch/avr32/mach-at32ap/pio.c
@@ -135,7 +135,28 @@
 	dump_stack();
 }
 
-/*--------------------------------------------------------------------------*/
+/* Reserve a pin, preventing anyone else from changing its configuration. */
+void __init at32_reserve_pin(unsigned int pin)
+{
+	struct pio_device *pio;
+	unsigned int pin_index = pin & 0x1f;
+
+	pio = gpio_to_pio(pin);
+	if (unlikely(!pio)) {
+		printk("pio: invalid pin %u\n", pin);
+		goto fail;
+	}
+
+	if (unlikely(test_and_set_bit(pin_index, &pio->pinmux_mask))) {
+		printk("%s: pin %u is busy\n", pio->name, pin_index);
+		goto fail;
+	}
+
+	return;
+
+fail:
+	dump_stack();
+}
 
 /*--------------------------------------------------------------------------*/
 
diff --git a/include/asm-avr32/arch-at32ap/portmux.h b/include/asm-avr32/arch-at32ap/portmux.h
index 2ba611e..9930871 100644
--- a/include/asm-avr32/arch-at32ap/portmux.h
+++ b/include/asm-avr32/arch-at32ap/portmux.h
@@ -23,5 +23,6 @@
 void at32_select_periph(unsigned int pin, unsigned int periph,
 			unsigned long flags);
 void at32_select_gpio(unsigned int pin, unsigned long flags);
+void at32_reserve_pin(unsigned int pin);
 
 #endif /* __ASM_ARCH_PORTMUX_H__ */