DFU: fix transitions between runtime and DFU mode

we now always go through a processor reset to avoid any state that might
be persistent/left-over during the switch.

firmware/atmel_softpack_libraries/libchip_sam3s/source/USBD_HAL.c

@@ -1163,10 +1163,20 @@ void USBD_IrqHandler(void)
 
         TRACE_INFO_WP("EoBRes ");
 
-#if defined(BOARD_USB_DFU) && defined(APPLICATION_dfu)
+#if defined(BOARD_USB_DFU)
+#if defined(APPLICATION_dfu)
+	/* if we are currently in the DFU bootloader, and we are beyond
+	 * the MANIFEST stage, we shall switch to the normal
+	 * application */
 	if (g_dfu->past_manifest)
 		USBDFU_SwitchToApp();
-#endif
+#else
+	/* if we are currently in the main application, and we are in
+	 * appDETACH state, switch into the DFU bootloader */
+	if (g_dfu->state == DFU_STATE_appDETACH)
+		DFURT_SwitchToDFU();
+#endif /* APPLICATION_dfu */
+#endif /* BOARD_USB_DFU */
 
         /* Flush and enable the Suspend interrupt */
         UDP->UDP_ICR = UDP_ICR_WAKEUP | UDP_ICR_RXRSM | UDP_ICR_RXSUSP;

firmware/atmel_softpack_libraries/usb/device/dfu/dfu.h

@@ -86,12 +86,11 @@ extern const USBDDriverDescriptors dfu_descriptors;
 /* magic value we use during boot to detect if we should start in DFU
  * mode or runtime mode */
 #define USB_DFU_MAGIC	0xDFDFDFDF
-/* RAM address for this magic value above */
-#define USB_DFU_MAGIC_ADDR	IRAM_ADDR
 
 /* The API between the core DFU handler and the board/soc specific code */
 
 struct dfudata {
+	uint32_t magic;
 	uint8_t status;
 	uint32_t state;
 	int past_manifest;

firmware/atmel_softpack_libraries/usb/device/dfu/dfu_driver.c

@@ -457,7 +457,7 @@ void USBDFU_Initialize(const USBDDriverDescriptors *pDescriptors)
 void USBDFU_SwitchToApp(void)
 {
 	/* make sure the MAGIC is not set to enter DFU again */
-	*(unsigned int *)USB_DFU_MAGIC_ADDR = 0;
+	g_dfu->magic = 0;
 
 	printf("switching to app\r\n");
 
@@ -468,7 +468,6 @@ void USBDFU_SwitchToApp(void)
 	__disable_irq();
 
 	/* Tell the hybrid to execute FTL JUMP! */
-	//BootIntoApp();
 	NVIC_SystemReset();
 }
 

firmware/atmel_softpack_libraries/usb/device/dfu/dfu_runtime.c

@@ -178,15 +178,17 @@ out:
 
 void DFURT_SwitchToDFU(void)
 {
-	unsigned int *dfu_except_tbl = (unsigned int *)IFLASH_ADDR;
+	/* store the magic value that the DFU loader can detect and
-	void (*toDFU)(void) = (void *)dfu_except_tbl[1];
+	 * activate itself, rather than boot into the application */
-
+	g_dfu->magic = USB_DFU_MAGIC;
-	*(unsigned int *)USB_DFU_MAGIC_ADDR = USB_DFU_MAGIC;
 
+	/* Disconnect the USB by remoting the pull-up */
 	USBD_Disconnect();
 	__disable_irq();
 
-	toDFU();
+	/* reset the processor, we will start execution with the
+	 * ResetVector of the bootloader */
+	NVIC_SystemReset();
 }
 
 void USBDCallbacks_RequestReceived(const USBGenericRequest *request)

firmware/libboard/common/source/board_cstartup_gnu.c

@@ -125,6 +125,7 @@ IntFunc exception_table[] = {
 };
 
 #if defined(BOARD_USB_DFU) && defined(APPLICATION_dfu)
+#include "usb/device/dfu/dfu.h"
 static void BootIntoApp(void)
 {
 	unsigned int *pSrc;
@@ -134,7 +135,7 @@ static void BootIntoApp(void)
 	SCB->VTOR = ((unsigned int)(pSrc)) | (0x0 << 7);
 	appReset = pSrc[1];
 
-	printf("Booting into App from %p, PC=%p\r\n", pSrc, appReset);
+	g_dfu->state = DFU_STATE_appIDLE;
 
 	appReset();
 }
@@ -153,8 +154,11 @@ void ResetException( void )
 
 
 #if defined(BOARD_USB_DFU) && defined(APPLICATION_dfu)
-    if (*(unsigned long *)IRAM_ADDR != 0xDFDFDFDF)
+    if (g_dfu->magic != USB_DFU_MAGIC) {
         BootIntoApp();
+        /* Infinite loop */
+        while ( 1 ) ;
+    }
 #endif
 
     /* Initialize the relocate segment */