| Shinya Kuribayashi | 880cc5a | 2008-04-22 22:47:27 +0900 | [diff] [blame] | 1 | |
| 2 | Notes for the MIPS architecture port of U-Boot |
| 3 | |
| 4 | Toolchains |
| 5 | ---------- |
| 6 | |
| 7 | http://www.denx.de/wiki/DULG/ELDK |
| 8 | ELDK < DULG < DENX |
| 9 | |
| 10 | http://www.emdebian.org/crosstools.html |
| 11 | Embedded Debian -- Cross-development toolchains |
| 12 | |
| 13 | http://buildroot.uclibc.org/ |
| 14 | Buildroot |
| 15 | |
| 16 | Known Issues |
| 17 | ------------ |
| 18 | |
| 19 | * Little endian build problem |
| 20 | |
| 21 | If use non-ELDK toolchains, -EB will be set to CPPFLAGS. Therefore all |
| 22 | objects will be generated in big-endian format. |
| 23 | |
| 24 | * Cache incoherency issue caused by do_bootelf_exec() at cmd_elf.c |
| 25 | |
| 26 | Cache will be disabled before entering the loaded ELF image without |
| 27 | writing back and invalidating cache lines. This leads to cache |
| 28 | incoherency in most cases, unless the code gets loaded after U-Boot |
| 29 | re-initializes the cache. The more common uImage 'bootm' command does |
| 30 | not suffer this problem. |
| 31 | |
| 32 | [workaround] To avoid this cache incoherency, |
| 33 | 1) insert flush_cache(all) before calling dcache_disable(), or |
| 34 | 2) fix dcache_disable() to do both flushing and disabling cache. |
| 35 | |
| 36 | * Note that Linux users need to kill dcache_disable() in do_bootelf_exec() |
| 37 | or override do_bootelf_exec() not to disable I-/D-caches, because most |
| 38 | Linux/MIPS ports don't re-enable caches after entering kernel_entry. |
| 39 | |
| 40 | TODOs |
| 41 | ----- |
| 42 | |
| 43 | * Probe CPU types, I-/D-cache and TLB size etc. automatically |
| 44 | |
| 45 | * Secondary cache support missing |
| 46 | |
| 47 | * Centralize the link directive files |
| 48 | |
| 49 | * Initialize TLB entries redardless of their use |
| 50 | |
| 51 | * R2000/R3000 class parts are not supported |
| 52 | |
| 53 | * Limited testing across different MIPS variants |
| 54 | |
| 55 | * Due to cache initialization issues, the DRAM on board must be |
| 56 | initialized in board specific assembler language before the cache init |
| 57 | code is run -- that is, initialize the DRAM in lowlevel_init(). |