\author: Cesar Fuguet
\date  : July 24, 2014

TSAR BOOT-LOADER

Files:
src/        Source files
            The entry point of this boot loader is the file reset.S

include/    Header files

driver/     Drivers source files and headers

conf/       Platform specific files

            For each platform, we must define a new directory.
            Mandatory files:

              - hard_config.h (can be generated using giet-vm genmap tool)

                This file contains all physical segments addresses and sizes of
                the hardware platform. It also contains other configuration
                definitions as the disk controller type, mesh size, etc.
                Examples can be found in the conf/ directory.

            Optional files:

              - platform.dts (platform device tree)

Makefile    Makefile to compile the boot loader.
            Mandatory arguments:

              - HARD_CONFIG_PATH=<platform_dir>

                Defines the directory where to find the hard_config.h file

           Optional arguments:

              - USE_DT=<value>

                Value can be 1 or 0. If a device tree file is not used, set
                this flag to 0. It is set by default to 1.

              - SYSTEM_CLK=<platform clock frequency>

                Platform clock frequency in KHz

              - DTS=<file.dts>

                Platform device tree (by default is platform.dts)

Important characteristics of this preloader:

  - Processor 0 performs loading of Operating System Boot Loader which must
    be an ELF file located at the third block of the disk.

  - Other processors wait to be waken up through an interruption generated
    from a XICU mailbox. Each processor other than 0 has its own mailbox
    in the local XICU.

  - Stack allocation is only made for processor 0. The loaded Operating System
    boot loader or kernel must perform stack allocation for other processors.

  - Stack for processor 0 is allocated at the end of RAM segment in the cluster
    (0,0).

Examples:

    make HARD_CONFIG_PATH=<platform_dir> USE_DT=0

        Compile for <platform_dir> and do not compile device tree file

    make HARD_CONFIG_PATH=<platform_dir> DTS=platform_fpga.dts SYSTEM_CLK=25000

        Compile for <platform_dir> and compile the 'platform_dpga.dts'
        device tree file. System clock frequency is 25 MHz

    make HARD_CONFIG_PATH=<platform_conf> SYSTEM_CLK=25000

        Compile for <platform_dir> and compile the 'platform.dts'
        device tree file (default name). System clock frequency is 25 MHz

