mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-30 00:21:06 +00:00
46 lines
1.5 KiB
Text
46 lines
1.5 KiB
Text
|
Generic TPL framework
|
||
|
|
=====================
|
||
|
|
|
||
|
|
Overview
|
||
|
|
--------
|
||
|
|
|
||
|
|
TPL---Third Program Loader.
|
||
|
|
|
||
|
|
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 TOPDIR/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:
|
||
|
|
#ifdef CONFIG_TPL_BUILD
|
||
|
|
#define CONFIG_SPL_LIBCOMMON_SUPPORT
|
||
|
|
#endif
|