uboot SPL Overview

最新推荐文章于 2023-02-23 19:53:20 发布

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本文介绍如何从U-Boot源代码树中构建一个适合SoC内部SRAM(≤64K)的小型U-Boot(SPL)，并引导实际的U-Boot到SDRAM中运行。文中详细列举了SPL的主要职责，包括基本ARM初始化、UART控制台初始化等，并提到了TI的X-Loader作为SPL的一种实现。

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Introduction:

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The idea is to build a mini u-boot(same as UBL in Davinci?) out of the u-boot tree that fits into SoC's internal SRAM (<=64K) and bootloads the real u-boot into the SDRAM, then the real u-boot will load the kernel into the SDRAM and boot it. :-).

Such a mini u-boot is typically called SPL(Second Program Loader) in u-boot terminology.

Duty of SPL:

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1> Basic ARM initialization

2> UART console initialization

3> Clocks and DPLL locking (minimal)

4> SDRAM initialization

5> Mux (minimal)

6> BootDevice initialization(based on where we are booting from.MMC1/MMC2/Nand/Onenand)

7> Bootloading real u-boot from the BootDevice and passing control to it.

BTW:

TI's X-loader is just one implemention of SPL out of the u-boot tree, And it depends on the u-boot source tree. same framework with u-boot. The u-boot guys will implement their own SPL in the tree. and then our system will boot without x-loader's help. :-)

Reference:

http://lists.denx.de/pipermail/u-boot/