diff --git a/arch/arm/src/stm32/stm32_gpio.c b/arch/arm/src/stm32/stm32_gpio.c
index 309df3520f..6787c57778 100644
--- a/arch/arm/src/stm32/stm32_gpio.c
+++ b/arch/arm/src/stm32/stm32_gpio.c
@@ -47,6 +47,8 @@
 #include <errno.h>
 #include <debug.h>
 
+#include <arch/irq.h>
+
 #include "up_arch.h"
 
 #include "chip.h"
@@ -202,7 +204,12 @@ static inline void stm32_gpioremap(void)
  *   Based on configuration within the .config file, it does:
  *    - Remaps positions of alternative functions. 
  * 
- * Typically called from stm32_start().
+ *   Typically called from stm32_start().
+ *
+ * Assumptions:
+ *   This function is called early in the initialization sequence so that
+ *   no mutual exlusion is necessary.
+ *
  ****************************************************************************/
 
 void stm32_gpioinit(void)
@@ -244,6 +251,7 @@ int stm32_configgpio(uint32_t cfgset)
   unsigned int pin;
   unsigned int pos;
   unsigned int modecnf;
+  irqstate_t flags;
   bool input;
  
   /* Verify that this hardware supports the select GPIO port */
@@ -278,6 +286,12 @@ int stm32_configgpio(uint32_t cfgset)
 
   input = ((cfgset & GPIO_INPUT) != 0);
 
+  /* Interrupts must be disabled from here on out so that we have mutually
+   * exclusive access to all of the GPIO configuration registers.
+   */
+
+  flags = irqsave();
+
   /* Decode the mode and configuration */
   
   regval  = getreg32(cr);
@@ -316,6 +330,7 @@ int stm32_configgpio(uint32_t cfgset)
         {
           /* Its an alternate function pin... we can return early */
 
+          irqrestore(flags);
           return OK;
         }
     }
@@ -342,6 +357,7 @@ int stm32_configgpio(uint32_t cfgset)
         {
           /* Neither... we can return early */
 
+          irqrestore(flags);
           return OK;
         }
     }
@@ -367,6 +383,8 @@ int stm32_configgpio(uint32_t cfgset)
   regval  = getreg32(regaddr);
   regval |= (1 << pin);
   putreg32(regval, regaddr);
+
+  irqrestore(flags);
   return OK;
 }
 #endif
@@ -386,6 +404,7 @@ int stm32_configgpio(uint32_t cfgset)
   unsigned int pin;
   unsigned int pos;
   unsigned int pinmode;
+  irqstate_t flags;
  
   /* Verify that this hardware supports the select GPIO port */
 
@@ -427,6 +446,14 @@ int stm32_configgpio(uint32_t cfgset)
         break;
     }
 
+  /* Interrupts must be disabled from here on out so that we have mutually
+   * exclusive access to all of the GPIO configuration registers.
+   */
+
+  flags = irqsave();
+
+  /* Now apply the configuration to the mode register */
+
   regval  = getreg32(base + STM32_GPIO_MODER_OFFSET);
   regval &= ~GPIO_MODER_MASK(pin);
   regval |= ((uint32_t)pinmode << GPIO_MODER_SHIFT(pin));
@@ -572,6 +599,7 @@ int stm32_configgpio(uint32_t cfgset)
       stm32_gpiowrite(cfgset, value);
     }
 
+  irqrestore(flags);
   return OK;
 }
 #endif
diff --git a/arch/mips/src/pic32mx/pic32mx-usbdev.c b/arch/mips/src/pic32mx/pic32mx-usbdev.c
index a857ac1627..bc0f450e40 100644
--- a/arch/mips/src/pic32mx/pic32mx-usbdev.c
+++ b/arch/mips/src/pic32mx/pic32mx-usbdev.c
@@ -5,9 +5,12 @@
  *   Author: Gregory Nutt <gnutt@nuttx.orgr>
  *
  * References:
- *   - This file derives from the STM32 USB device driver
+ *   This file derives from the STM32 USB device driver with modifications
+ *   based on additional information from:
+ *
  *   - "USB On-The-Go (OTG)", DS61126E, Microchip Technology Inc., 2009
- *   - Sample code provided with the Sure Electronics PIC32 board.
+ *   - Sample code provided with the Sure Electronics PIC32 board
+ *     (which seems to have derived from Microchip PICDEM PIC18 code).
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -2010,7 +2013,7 @@ static void pic32mx_ep0transfer(struct pic32mx_usbdev_s *priv, uint16_t status)
 
       /* Check the current EP0 OUT buffer contains a SETUP packet */
 
-      if (((bdt->status & USB_BDT_PID_MASK) >> USB_BDT_PID_SHIFT) == USB_SETUP_TOKEN)
+      if (((bdt->status & USB_BDT_PID_MASK) >> USB_BDT_PID_SHIFT) == USB_PID_SETUP_TOKEN)
         {
           /* Check if the SETUP transaction data went into the priv->ctrl
            * buffer. If not, then we will need to copy it.