add failed safe mbr forward address

Author: hathach

lib/sdk11/components/libraries/bootloader_dfu/bootloader.c

@@ -345,13 +345,14 @@ void bootloader_app_start(void)
   NVIC->ICPR[1]=0xFFFFFFFF;
 #endif
 
+  uint32_t fwd_ret;
   uint32_t app_addr;
 
   if ( is_sd_existed() )
   {
     // App starts after SoftDevice
     app_addr = SD_SIZE_GET(MBR_SIZE);
-    sd_softdevice_vector_table_base_set(app_addr);
+    fwd_ret = sd_softdevice_vector_table_base_set(app_addr);
   }else
   {
     // App starts right after MBR
@@ -362,7 +363,14 @@ void bootloader_app_start(void)
       .params.irq_forward_address_set.address = app_addr,
     };
 
-    sd_mbr_command(&command);
+    fwd_ret = sd_mbr_command(&command);
+  }
+
+  // unlikely failed to forward vector table, manually set forward address
+  if ( fwd_ret != NRF_SUCCESS )
+  {
+    // MBR use first 4-bytes of SRAM to store foward address
+    *(uint32_t *)(0x20000000) = app_addr;
   }
 
   // jump to app

src/flash_nrf5x.c

@@ -37,6 +37,7 @@ void flash_nrf5x_flush (bool need_erase)
 {
   if ( _fl_addr == FLASH_CACHE_INVALID_ADDR ) return;
 
+  // skip the write if contents matches
   if ( memcmp(_fl_buf, (void *) _fl_addr, FLASH_PAGE_SIZE) != 0 )
   {
     // - nRF52832 dfu via uart can miss incoming byte when erasing because cpu is blocked for > 2ms.