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- Generic TPL framework
- =====================
- Overview
- TPL
- Due to the SPL on some boards(powerpc mpc85xx) has a size limit and cannot
- be compatible with all the external device(e.g. DDR). So add a tertiary
- program loader (TPL) to enable a loader stub loaded by the code from the
- SPL. It loads the final uboot image into DDR, then jump to it to begin
- execution. Now, only the powerpc mpc85xx has this requirement and will
- implemente it.
- Keep consistent with SPL, with this framework almost all source files for a
- board can be reused. No code duplication or symlinking is necessary anymore.
- How it works
- There has been a directory $(srctree)/spl which contains only a Makefile. The
- Makefile is shared by SPL and TPL.
- The object files are built separately for SPL/TPL and placed in the
- directory spl/tpl. The final binaries which are generated are
- u-boot-{spl|tpl}, u-boot-{spl|tpl}.bin and u-boot-{spl|tpl}.map.
- During the TPL build a variable named CONFIG_TPL_BUILD is exported in the
- make environment and also appended to CPPFLAGS with -DCONFIG_TPL_BUILD.
- The SPL options are shared by SPL and TPL, the board config file should
- determine which SPL options to choose based on whether CONFIG_TPL_BUILD
- is set. Source files can be compiled for TPL with options choosed in the
- board config file.
- For example:
- spl/Makefile:
- LIBS-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += common/libcommon.o
- CONFIG_SPL_LIBCOMMON_SUPPORT is defined in board config file:
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