This document explains how to set up a basic Buildroot system on various
Atmel boards. Additional details can also be found on the Linux4SAM website:
http://www.at91.com/linux4sam/bin/view/Linux4SAM/

This guide covers the following configurations:
 - at91sam9g45m10ek_defconfig
 - at91sam9rlek_defconfig
 - at91sam9x5ek_defconfig (at91sam9g15, at91sam9g25, at91sam9x25,
   at91sam9g35 and at91sam9x35)
 - atmel_sama5d3xek_defconfig (sama5d31, sama5d33, sama5d34, sama5d35,
   sama5d36)
 - atmel_sama5d3_xplained_defconfig
 - atmel_sama5d3_xplained_mmc_defconfig
 - atmel_sama5d4ek_defconfig
 - atmel_sama5d4_xplained_defconfig
 - atmel_sama5d4_xplained_mmc_defconfig
 - atmel_sama5d2_xplained_mmc_defconfig

These configurations will use AT91Bootstrap, u-boot and a linux kernel from
the git trees maintained by Atmel.

Configuring and building Buildroot
==================================

For most configurations listed above, the Buildroot configuration
assumes the system will be flashed on NAND. In this case, after
building Buildroot, follow the instructions in the "Flashing the NAND
using SAM-BA" section below.

For the Xplained boards, an alternative Buildroot configuration is
provided to boot from an SD card. Those configurations are labeled as
'mmc'. In this case, after building Buildroot, follow the instructions
in the "Preparting the SD card" sction.

To configure and build Buildroot, run:

  make <board>_defconfig
  make

Flashing the NAND using SAM-BA
==============================

Flashing the board
------------------

Connect the board:
 o at91sam9g45m10ek: DBGU: J10, USB sam-ba: J14
 o at91sam9rlek: DBGU: J19, USB sam-ba: J21
 o at91sam9x5ek: DBGU: J11, USB sam-ba: J20
 o sama5d3xek: DBGU: J14, USB sam-ba: J20
 o sama5d3 Xplained: DBGU: J23, USB sam-ba: J6
 o sama5d4ek: DBGU: J22 or J24, USB sam-ba: J1
 o sama5d4 Xplained: DBGU: J1, USB sam-ba: J11

Start the board in RomBOOT:
 o at91sam9g45m10ek:
    1. open JP8, JP10 and JP12
    2. start the board
    3. close JP8, JP10 and JP12

 o at91sam9rlek:
   1. J11 on 1-2 (BMS=1), open J12 and J13
   2. start the board
   3. close J12 and J13

 o at91sam9x5ek:
   1. open JP9 and:
      - Cogent: open *NCS jumper
      - Embest: open SW1
      - Ronetix: open J1 and J2
   2. start the board
   3. close JP9 and:
      - Cogent: close *NCS jumper
      - Embest: close SW1 (ON position)
      - Ronetix: close J1 and J2

 o sama5d3xek:
   1. start the board
   2. push BP4 and BP1
   3. release BP1
   4. release BP4

 o sama5d3 Xplained:
   1. open JP5 (NANDCS) and JP6 (SPICS)
   2. start the board
   3. close JP5 ans JP6

 o sama5d4ek:
   1. start the board
   2. push BP3 and BP4
   3. release BP4
   4. release BP3

 o sama5d4 Xplained:
   1. close JP7 (BOOT_DIS)
   2. start the board
   3. open JP7

"RomBOOT" should appear on your console (this should be ttyUSBx or ttyACMx)

Now locate the USB sam-ba interface it should be ttyACMx, usually ttyACM0
dmesg on your machine should give:
usb 1-2.1.4: New USB device found, idVendor=03eb, idProduct=6124
usb 1-2.1.4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
cdc_acm 1-2.1.4:1.0: ttyACM0: USB ACM device

Look for idVendor=03eb, idProduct=6124, this is the interface you want to use.

You can then flash the board using the provided flasher.sh script in board/atmel:

board/atmel/flasher.sh <builddir_path> <interface> <board>

For example, for an out of tree build made in
/tmp/atmel_sama5d3_xplained/ for the sama5d3 Xplained, you would use:
board/atmel/flasher.sh /tmp/atmel_sama5d3_xplained/ /dev/ttyACM0 sama5d3_xplained

Reboot, the system should boot up to the buildroot login invite.

Preparing the SD card
=====================

The SD card must be partitioned with at least two partitions: one
FAT16 partition for the bootloaders, kernel image and Device Tree
blob, and one ext4 partition for the root filesystem. To partition the
SD card:

sudo sfdisk /dev/mmcblk0 <<EOF
,64MiB,6
;
EOF

This creates a 64 MB partition for the FAT16 filesystem (type 6) and
uses the rest for the ext4 filesystem used for the root filesystem.

Then, format both partitions:

sudo mkfs.msdos -n boot /dev/mmcblk0p1
sudo mkfs.ext4 -L rootfs -O ^huge_file /dev/mmcblk0p2

 Note: the -O ^huge_file option is needed to avoid enabling the huge
 files features of ext4 (to support files larges than 2 TB), which
 needs the kernel option CONFIG_LBDAF to be enabled.

Mount both partitions (if not done automatically by your system):

sudo mount /dev/mmcblk0p1 /media/boot
sudo mount /dev/mmcblk0p2 /media/rootfs

Copy the bootloaders, kernel image and Device Tree blob to the first
partition:

cp output/images/boot.bin /media/boot/
cp output/images/u-boot.bin /media/boot/
cp output/images/zImage /media/boot/
cp output/images/at91-sama5d2_xplained.dtb /media/boot/

Extract the root filesystem to the second partition:

sudo tar -C /media/rootfs -xf output/images/rootfs.tar

Unmount both partitions:

sudo umount /media/boot
sudo umount /media/rootfs

Insert your SD card in your Xplained board, and enjoy. The default
U-Boot environment will properly load the kernel and Device Tree blob
from the first partition of the SD card, so everything works
automatically.