Update some instructions

docs/spi.md

@@ -22,34 +22,45 @@ Refer to [U-Boot](/uboot) page to build the image.
 
 2. Bootable U-Boot on microSD card.
 
-### Using Linux
+### Generic Linux
 
 !!! info
     Concurrent access on SPI NOR and SATA drive can lead to unstable SATA. The following instructions has taken this issue into consideration and workaround it by disabling the SATA temporary.
 
-Put u-boot binaries on home folder and rename it as **u-boot-spi.bin**.
+  1) Put u-boot binaries on home folder and rename it as **u-boot-spi.bin**.
-Download boot_spi_en.scr from [here](/files/software/boot_spi_en.scr) and put it to / and then reboot the system
+
+  2) Download boot_spi_en.scr from [here](/files/software/boot_spi_en.scr) and put it to /boot/ and then reboot the system
 ```
-sudo wget https://wiki.kobol.io/files/software/boot_spi_en.scr -O /boot_spi_en.scr
+sudo wget https://wiki.kobol.io/files/software/boot_spi_en.scr -O /boot/boot_spi_en.scr
 sudo reboot
 ```
 
-Switch to Helios4 serial console. Press any key to cancel the autoboot and execute these commands
+!!! info
+    Source code of boot_spi_en.scr can be downloaded from [here](/files/software/boot_spi_en.cmd)
+
+  3) Switch to Helios4 serial console. Press any key to cancel the autoboot and execute these commands
 ```
-setenv script_name "boot_spi_en.scr"
+setenv script_name "/boot/boot_spi_en.scr"
 stage_boot mmc_scr
 ```
+
 It will boot to Linux with modified device tree.
 
-- - -
+4) Log in to Helios4, verify whether mtdblock0 is exist using **lsblk**
-
+```
-Log in to Helios4, verify whether mtdblock0 is exist using **lsblk**, and write the u-boot to SPI flash using this command
+lsblk
+NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
+mtdblock0    31:0    0    4M  0 disk
+mmcblk0     179:0    0 14.9G  0 disk
+└─mmcblk0p1 179:1    0 14.8G  0 part /
+```
 
+5) Write the u-boot to SPI flash using this command
 ```
 sudo dd if=~/u-boot-spi.bin of=/dev/mtdblock0
 ```
 
-Set DIP switches SW1 to SPI Boot
+6) Set DIP switches SW1 to SPI Boot
 
 ![Boot from SPI](/img/hardware/dipswitch_boot_spinor.png)
 
@@ -61,9 +72,29 @@ BootROM - 1.73
 Booting from SPI flash
 ```
 
-## Set Up U-Boot
+### Armbian
 
-Add U-Boot ENV variable.
+!!! info
+	Preliminary
+
+1) Open /boot/armbianEnv.txt and modify *spi_workaround="on"*
+
+2) Reboot the system to apply the change
+
+3) Login to the system and run
+```
+sudo nand-sata-install
+```
+
+4) Select option **5 Install the bootloader to SPI Flash**
+
+
+## Set Up U-Boot Environment
+
+!!! info
+    The prebuilt SPI image has been configured to automatically run /boot/boot.scr and /boot.scr on microSD or USB drive. There is no need to set up u-boot environment to boot Armbian.
+
+Add U-Boot ENV variables to prevent U-Boot to relocate fdt and initrd into RAM address that is not accessible by kernel, and set the correct device tree name for Helios4 board
 
 ```
 setenv fdt_high 0xffffffff
@@ -72,7 +103,7 @@ setenv fdtfile armada-388-helios4.dtb
 saveenv
 ```
 
-To automatically boot Linux on microSD card
+- To automatically boot Linux on microSD card
 
 ```
 setenv bootargs '${console} root=/dev/mmcblk0p1 rootwait'
@@ -80,6 +111,14 @@ setenv bootcmd 'ext2load mmc 0:1 ${kernel_addr_r} /boot/zImage; ext2load mmc 0:1
 saveenv
 ```
 
-!!! info
+- To automatically boot Linux on USB drive (assume UUID=1234)
-    The prebuilt SPI image has been configured to automatically run /boot/boot.scr and /boot.scr on microSD. There is no need to configure u-boot to boot Armbian on microSD.
 
+```
+setenv bootargs '${console} root=UUID=1234 rootwait'
+setenv bootcmd 'ext2load usb 0:1 ${kernel_addr_r} /boot/zImage; ext2load usb 0:1 ${ramdisk_addr_r} /boot/uInitrd; ext2load usb 0:1 ${fdt_addr} /boot/dtb/${fdtfile}; bootz ${kernel_addr_r}  ${ramdisk_addr_r} ${fdt_addr}'
+saveenv
+```
+
+## Moving Rootfs to Other Device
+
+Please refer to [Armbian](/armbian) page to move the rootfs from microSD to USB using *nand-sata-install* utility.