# AT91Bootstrap Project

AT91Bootstrap is the 2nd level bootloader for Microchip microprocessors (aka AT91).
It providing a set of algorithms to manage the hardware initialization such as
clock speed configuration, PIO settings, DRAM initialization, to download your
main application from specified boot media: NAND FLASH, serial FLASH (both
AT25-compatible of DataFlash), serial EEPROM, SD Card, etc. to main memory and
to start it.

1 Host Setup
================================================================================

## 1.1 Generic Requirements

Python3
 - needed by the scripts that prepend the PMECC header for the NAND flash boot

## 1.2 Linux Host Requirements

Refer to the GNU ARM Toolchain section below for toolchain recommendations.

We recommend using a GNU Make with a version of 4.2 or newer.

## 1.3 Windows Host Setup

### 1.3.1 Install required tools

A toolchain such as GNU Tools for Arm Embedded Processors shall be provided.
Get one from e.g. <https://developer.arm.com/open-source/gnu-toolchain/gnu-rm>.
Run the installation wizard and specify a destination folder whose full path is
free from any whitespace.
Further instructions below are written as if the toolchain had been installed
to C:\opt\gnu_tools_arm\7-2018-q2.

Building AT91Bootstrap requires a POSIX environment. Several tools are available
on the market to provide such an environment. In these instructions we rely on
Minimal SYStem 2 (MSYS2).
Get MSYS2 from <http://www.msys2.org>.
Install it. The installation wizard ask for the installation folder, and
suggests to keep its full path short.
Further instructions below are written as if MSYS2 had been installed to
C:\opt\msys.

MSYS2 notably provides a minimal Bourne Shell, named mintty.
Launch mintty in the "MSYS2 MSYS" configuration: either search for the
"MSYS2 MSYS" shortcut in the Program menu, or invoke the Run dialog
('Windows' and 'R' key combination) and enter the following command at the Open
prompt:

    C:\opt\msys\msys2_shell.cmd -msys

In this terminal, whose prompt is suffixed with "MSYS", request the package
manager to update both its database and the packages already installed:

    $ pacman -Syuu

Still at the "MSYS" prompt, install additional packages that we will need later
on when building AT91Bootstrap:

    $ pacman -S bc gawk gcc git make python tar

Finally, close the "MSYS2 MSYS" terminal window.

### 1.3.2 Open a shell suitable for building AT91Bootstrap

Launch mintty in the "MSYS2 MinGW 64-bit" configuration: either search for the
"MSYS2 MinGW 64-bit" shortcut in the Program menu, or invoke the Run dialog
('Windows' and 'R' key combination) and enter the following command at the Open
prompt:

    C:\opt\msys\msys2_shell.cmd -mingw64

In this terminal, whose prompt is suffixed with "MINGW64", configure environment
variables:

    $ export CROSS_COMPILE="arm-none-eabi-"
    $ export PATH=/c/opt/gnu_tools_arm/7-2018-q2/bin:$PATH

Still at the "MINGW64" prompt, proceed with instructions given in the Compile
AT91Bootstrap section below.

2 GNU ARM Toolchain
================================================================================

AT91Bootstrap has been compiled and tested under Linux using the following GNU
ARM Toolchain:
- gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
- gcc version 4.7.3 (Sourcery CodeBench Lite 2013.05-24)
- gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)
- gcc version 4.8.3 (Sourcery CodeBench Lite 2014.05-29)
- gcc version 4.9.3 (Linaro GCC 2014.11)
- gcc version 5.1.1 (Linaro GCC 5.1-2015.08)
- gcc version 7.2.1 (Linaro GCC 7.2-2017.11)
- gcc version 7.3.1 (Linaro GCC 7.2-2018.05)
- gcc version 7.5.0 (Linaro GCC 7.5-2019.12)
- gcc version 8.2.0 (Ubuntu 8.2.0-7ubuntu1)
- gcc version 10.2.1 20201103 (GNU Toolchain for the A-profile Architecture 10.2-2020.11 (arm-10.16))

WARNING: check KNOWN_ISSUES for issues with older gcc versions. We recommend
using a toolchain newer than 6.0.

3 Compile AT91Bootstrap
================================================================================

## 3.1 Compile DataFlashBoot

Let's use at91sam9x5ek as an example.

### 3.1.1 Compile booting u-boot image from DataFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9x5ekdf_uboot_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.1.2 Compile booting kernel image from DataFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9x5ekdf_linux_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.1.3 Compile booting kernel & dt image from DataFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9x5ekdf_linux_dt_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

## 3.2 Compile NandFlashBoot

Let's use at91sam9m10g45ek as an example.

### 3.2.1 Compile booting u-boot image from NandFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eknf_uboot_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.2.2 Compile booting kernel image from NandFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eknf_linux_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.2.3 Compile booting kernel & dt image from NandFlash

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eknf_linux_dt_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

## 3.3 Compile SDCardBoot

Let's use at91sam9m10g45ek as an example,

### 3.3.1 Compile booting u-boot image from SDCard

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eksd_uboot_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.3.2 Compile booting linux image from SDCard

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eksd_linux_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

### 3.3.3 Compile booting linux & dt image from SDCard

    $ cd <project directory>
    $ make mrproper
    $ make at91sam9m10g45eksd_linux_dt_defconfig
    $ make

If the building process is successful, the final .bin image can be found under
binaries/

4 Release
================================================================================
If you plan to release the project, you can use the command as below

    $ cd <project directory>
    $ make tarball

If the command is successful, the .tar.gz tar package can be found under
the project top directory.

5 Others
================================================================================

## 5.1 About booting from NOR flash.

### 5.1.1 ROM Code version

Booting from the external NOR flash is supported in ROM code v2.1
for SAMA5D3x. Bootstrap relocates the binary to the internal SRAM and run.

### 5.1.2 SAM-BA

Using SAM-BA to program the binary to the NOR flash is a little different
from other booting mode. Namely, there is no 'Send Boot File' command for
NOR flash.

You should use 'Send File' command to send the binary file the same like
for a normal file, with 'Address' selected to 0.

6 Contributing your own board
================================================================================

If the system board that you have is not listed, then you will need
to port AT91Bootstrap to your hardware platform. To do this, follow these
steps:

1\. Create a new directory to hold your board specific code under
  contrib/board/ directory. Add any files you need.  
  In your board directory, you will need at least the "board.mk",
  a "<board>.c", "<board>.h", "Config.in.board", and "Config.in.boardname".  
2\. Create the necessary default configuration files such as
  "<board>df_uboot_defconfig" in your new board directory.  
3\. Add(source) your board's "Config.in.board" in "contrib/board/Config.in.board" file.  
4\. Add(source) your board's "Config.in.boardname" in the "contrib/board/Config.in.boardname" file.  
5\. Add your board's "<board>.h" in the "contrib/include/contrib_board.h" file.  
6\. Run "make <board>df_uboot_defconfig" with your new name.  
7\. Type "make", and you should get the final .bin image can be found under
  the binaries/ directory.  

7 Contributing
================================================================================

To contribute to AT91Bootstrap you should submit the patches for review to
the github pull-request facility directly or the forum. And don't forget to
Cc the maintainers.

Microchip Forum:

https://www.microchip.com/forums/f542.aspx

Maintainers:

Eugen Hristev <eugen.hristev@microchip.com>

Nicolas Ferre <nicolas.ferre@microchip.com>

When creating patches insert the [at91bootstrap] tag in the subject, for example
use something like:

    git format-patch -s --subject-prefix='at91bootstrap][PATCH' <origin>

-End-
