NOR flash boot for versatile uboot

最新推荐文章于 2024-12-01 21:20:49 发布

elainezhang09

最新推荐文章于 2024-12-01 21:20:49 发布

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分类专栏： Linux 文章标签： flash vector function table go

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本文介绍如何通过修改U-Boot使系统能直接从NOR Flash启动，绕过Boot_Monitor阶段。主要内容包括初始化SDRAM、设置REMAP寄存器进行地址重映射以及复制异常向量表到内存起始地址。

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ARM versatile uboot 实现过程，是假设ARM Boot_Monitor先于uboot运行。如果想脱离Boot_Monitor 实现由uboot的NOR flash 启动，需要做以下修改。

Revision to code tree

To enable autoboot from uboot, i.e. get rid of Boot_Monitor from the booting phase, following should be done

1. Init SDRAM

This can be done in lowlevel_init.S in the board/versatile folder. The SDRAM init could be copied from Boot_Monitor: platform code sysboot.S

2. Enable REMAP

after cpu_init function, set PC to PC+ #NOR_FLASH (when NOR_FLASH boot enabled, NOR_FLASH could be seen from both address 0x0 and the real 0x34000000 address.); set REMAP register. After remap, the 0x0 is the SDRAM space. Relocation could be done after this, by copying the code (adr r0, _start) to link address (TEXT_BASE). PC could then go back to the linked address and run.

3. Copy the vector table

copy the expection vector table to 0x0