Back port some A10 changes into the SAMA5 memory map definitions

arch/arm/src/a1x/chip/a10_memorymap.h

@@ -540,7 +540,8 @@
 
 #  define VECTOR_L2_END_PADDR     (VECTOR_L2_PBASE+VECTOR_L2_SIZE)
 #  define VECTOR_L2_END_VADDR     (VECTOR_L2_VBASE+VECTOR_L2_SIZE)
-#endif
+
+#endif /* !CONFIG_ARCH_LOWVECTORS */
 
 /* Paging L2 page table offset/size */
 
@@ -572,11 +573,15 @@
  */
 
 #define VECTOR_TABLE_SIZE         0x00010000
+
 #ifdef CONFIG_ARCH_LOWVECTORS  /* Vectors located at 0x0000:0000  */
+
 #  define A1X_VECTOR_PADDR        A1X_SRAMA1_PADDR
 #  define A1X_VECTOR_VSRAM        A1X_SRAMA1_VADDR
 #  define A1X_VECTOR_VADDR        0x00000000
+
 #else  /* Vectors located at 0xffff:0000 -- this probably does not work */
+
 #  ifdef A1X_ISRAM1_SIZE >= VECTOR_TABLE_SIZE
 #    define A1X_VECTOR_PADDR      (A1X_SRAMA1_PADDR+A1X_ISRAM1_SIZE-VECTOR_TABLE_SIZE)
 #    define A1X_VECTOR_VSRAM      (A1X_SRAMA1_VADDR+A1X_ISRAM1_SIZE-VECTOR_TABLE_SIZE)
@@ -585,6 +590,7 @@
 #    define A1X_VECTOR_VSRAM      (A1X_SRAMA1_VADDR+A1X_ISRAM0_SIZE-VECTOR_TABLE_SIZE)
 #  endif
 #  define A1X_VECTOR_VADDR        0xffff0000
+
 #endif
 
 /************************************************************************************

configs/pcduino-a10/README.txt

@@ -101,6 +101,7 @@ Contents
   - Serial Console
   - LEDs
   - Buttons
+  - Booting NuttX from an SD card
 
 pcDuino v1 Connectors
 =====================
@@ -249,3 +250,17 @@ Buttons
     SW4 Key_Home  LCD1_D18/ATAD14/KP_OUT0/SMC_SLK/EINT18/CSI1_D18/PH18
     SW5 Key_Menu  LCD1_D19/ATAD15/KP_OUT1/SMC_SDA/EINT19/CSI1_D19/PH19
 
+Booting NuttX from an SD card
+=============================
+
+  These are the steps to get U-Boot booting from SD Card:
+
+  $ git clone https://github.com/yuq/u-boot-sunxi.git
+  $ cd u-boot-sunxi
+  $ make pcduino CROSS_COMPILE=arm-linux-gnueabi-
+  $ sudo dd if=./spl/sunxi-spl.bin of=/dev/sdb bs=1024 seek=8
+  $ sudo dd if=u-boot.bin of=/dev/sdb bs=1024 seek=32
+
+  We need to replace u-boot.bin by nuttx.bin.
+
+  Reference: https://www.olimex.com/wiki/Bare_Metal_programming_A13#Stand_alone_program_running_with_uboot