From 5f2c16dab20281f427c1138f33cefeb2e9785b7e Mon Sep 17 00:00:00 2001 From: Bin Meng Date: Thu, 18 Jul 2019 00:34:03 -0700 Subject: doc: arch: Convert README.mips to reST Convert plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Bin Meng Reviewed-by: Heinrich Schuchardt --- doc/arch/index.rst | 2 ++ doc/arch/mips.rst | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+) create mode 100644 doc/arch/mips.rst (limited to 'doc/arch') diff --git a/doc/arch/index.rst b/doc/arch/index.rst index a03ee6b752..1aeb7a1327 100644 --- a/doc/arch/index.rst +++ b/doc/arch/index.rst @@ -5,3 +5,5 @@ Architecture-specific doc .. toctree:: :maxdepth: 2 + + mips diff --git a/doc/arch/mips.rst b/doc/arch/mips.rst new file mode 100644 index 0000000000..b8166087dd --- /dev/null +++ b/doc/arch/mips.rst @@ -0,0 +1,46 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +MIPS +==== + +Notes for the MIPS architecture port of U-Boot + +Toolchains +---------- + + * `ELDK < DULG < DENX `_ + * `Embedded Debian -- Cross-development toolchains `_ + * `Buildroot `_ + +Known Issues +------------ + + * Cache incoherency issue caused by do_bootelf_exec() at cmd_elf.c + + Cache will be disabled before entering the loaded ELF image without + writing back and invalidating cache lines. This leads to cache + incoherency in most cases, unless the code gets loaded after U-Boot + re-initializes the cache. The more common uImage 'bootm' command does + not suffer this problem. + + [workaround] To avoid this cache incoherency: + - insert flush_cache(all) before calling dcache_disable(), or + - fix dcache_disable() to do both flushing and disabling cache. + + * Note that Linux users need to kill dcache_disable() in do_bootelf_exec() + or override do_bootelf_exec() not to disable I-/D-caches, because most + Linux/MIPS ports don't re-enable caches after entering kernel_entry. + +TODOs +----- + + * Probe CPU types, I-/D-cache and TLB size etc. automatically + * Secondary cache support missing + * Initialize TLB entries redardless of their use + * R2000/R3000 class parts are not supported + * Limited testing across different MIPS variants + * Due to cache initialization issues, the DRAM on board must be + initialized in board specific assembler language before the cache init + code is run -- that is, initialize the DRAM in lowlevel_init(). + * centralize/share more CPU code of MIPS32, MIPS64 and XBurst + * support Qemu Malta -- cgit v1.2.3