原创 【博客大赛】U-Boot for AM335x (1) U-Boot Design Principles

The 10 Golden Rules of U-Boot design:
    1. Keep it Small
    2. Keep it Fast
    3. Keep it Simple
    4. Keep it Portable
    5. Keep it Configurable
    6. Keep it Debuggable
    7. Keep it Usable
    8. Keep it Maintainable
    9. Keep it Beautiful
    10. Keep it Open

from http://www.denx.de/wiki/U-Boot/DesignPrinciples
这么有道理的东东，拿来当一楼。

AM335x的核心板，除了CPU之外，还包括SRAM、NandFlash和PMIC（电源管理）。这次我用的是Forlinx的OK335D开发板，烧写方式是从SD卡启动并将存储在其中的MLO、u-boot.img、uImage、ubi.img拷贝到NandFlash对应位置；拔掉SD卡重新上电，找到NandFlash开始运行，先执行MLO和u-boot.img，然后解压内核并运行它。

MLO和u-boot.img都属于U-Boot，它至少要完成的工作有：

Configure the memory system.
Load the kernel image at the correct memory address.
Optionally load an initial RAM disk at the correct memory address.
Initialise the boot parameters to pass to the kernel.
Obtain the ARM Linux machine type
Enter the kernel with the appropriate register values.

It is usually expected that the bootloader will initialise a serial or video console for the kernel in addition to these basic tasks. Indeed a serial port is almost considered mandatory in most system configurations.

from http://www.simtec.co.uk/products/SWLINUX/files/booting_article.html

如果是自己设计的AM335x的核心板，更换了PMIC、SRAM、NandFlash等等，对U-Boot的修改就更必不可少。