1*4882a593SmuzhiyunGeneric TPL framework 2*4882a593Smuzhiyun===================== 3*4882a593Smuzhiyun 4*4882a593SmuzhiyunOverview 5*4882a593Smuzhiyun-------- 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunTPL---Third Program Loader. 8*4882a593Smuzhiyun 9*4882a593SmuzhiyunDue to the SPL on some boards(powerpc mpc85xx) has a size limit and cannot 10*4882a593Smuzhiyunbe compatible with all the external device(e.g. DDR). So add a tertiary 11*4882a593Smuzhiyunprogram loader (TPL) to enable a loader stub loaded by the code from the 12*4882a593SmuzhiyunSPL. It loads the final uboot image into DDR, then jump to it to begin 13*4882a593Smuzhiyunexecution. Now, only the powerpc mpc85xx has this requirement and will 14*4882a593Smuzhiyunimplemente it. 15*4882a593Smuzhiyun 16*4882a593SmuzhiyunKeep consistent with SPL, with this framework almost all source files for a 17*4882a593Smuzhiyunboard can be reused. No code duplication or symlinking is necessary anymore. 18*4882a593Smuzhiyun 19*4882a593SmuzhiyunHow it works 20*4882a593Smuzhiyun------------ 21*4882a593Smuzhiyun 22*4882a593SmuzhiyunThere has been a directory $(srctree)/spl which contains only a Makefile. The 23*4882a593SmuzhiyunMakefile is shared by SPL and TPL. 24*4882a593Smuzhiyun 25*4882a593SmuzhiyunThe object files are built separately for SPL/TPL and placed in the 26*4882a593Smuzhiyundirectory spl/tpl. The final binaries which are generated are 27*4882a593Smuzhiyunu-boot-{spl|tpl}, u-boot-{spl|tpl}.bin and u-boot-{spl|tpl}.map. 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunDuring the TPL build a variable named CONFIG_TPL_BUILD is exported in the 30*4882a593Smuzhiyunmake environment and also appended to CPPFLAGS with -DCONFIG_TPL_BUILD. 31*4882a593Smuzhiyun 32*4882a593SmuzhiyunThe SPL options are shared by SPL and TPL, the board config file should 33*4882a593Smuzhiyundetermine which SPL options to choose based on whether CONFIG_TPL_BUILD 34*4882a593Smuzhiyunis set. Source files can be compiled for TPL with options choosed in the 35*4882a593Smuzhiyunboard config file. 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunFor example: 38*4882a593Smuzhiyun 39*4882a593Smuzhiyunspl/Makefile: 40*4882a593SmuzhiyunLIBS-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += common/libcommon.o 41*4882a593Smuzhiyun 42*4882a593SmuzhiyunCONFIG_SPL_LIBCOMMON_SUPPORT is defined in board config file: 43*4882a593Smuzhiyun#ifdef CONFIG_TPL_BUILD 44*4882a593Smuzhiyun#define CONFIG_SPL_LIBCOMMON_SUPPORT 45*4882a593Smuzhiyun#endif 46