xref: /openbmc/u-boot/doc/README.mips (revision aefb8f4c)
1
2Notes for the MIPS architecture port of U-Boot
3
4Toolchains
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
16Known Issues
17------------
18
19  * Cache incoherency issue caused by do_bootelf_exec() at cmd_elf.c
20
21    Cache will be disabled before entering the loaded ELF image without
22    writing back and invalidating cache lines. This leads to cache
23    incoherency in most cases, unless the code gets loaded after U-Boot
24    re-initializes the cache. The more common uImage 'bootm' command does
25    not suffer this problem.
26
27    [workaround] To avoid this cache incoherency,
28    1) insert flush_cache(all) before calling dcache_disable(), or
29    2) fix dcache_disable() to do both flushing and disabling cache.
30
31  * Note that Linux users need to kill dcache_disable() in do_bootelf_exec()
32    or override do_bootelf_exec() not to disable I-/D-caches, because most
33    Linux/MIPS ports don't re-enable caches after entering kernel_entry.
34
35TODOs
36-----
37
38  * Probe CPU types, I-/D-cache and TLB size etc. automatically
39
40  * Secondary cache support missing
41
42  * Initialize TLB entries redardless of their use
43
44  * R2000/R3000 class parts are not supported
45
46  * Limited testing across different MIPS variants
47
48  * Due to cache initialization issues, the DRAM on board must be
49    initialized in board specific assembler language before the cache init
50    code is run -- that is, initialize the DRAM in lowlevel_init().
51
52  * centralize/share more CPU code of MIPS32, MIPS64 and XBurst
53
54  * support Qemu Malta
55