[u-boot.git] / doc / README.mips


Notes for the MIPS architecture port of U-Boot

Toolchains
----------

  http://www.denx.de/wiki/DULG/ELDK
  ELDK < DULG < DENX

  http://www.emdebian.org/crosstools.html
  Embedded Debian -- Cross-development toolchains

  http://buildroot.uclibc.org/
  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,
    1) insert flush_cache(all) before calling dcache_disable(), or
    2) 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
Commit	Line	Data
4a1f11b4 SK	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
4a1f11b4 SK	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
	35	TODOs
	36	-----
	37
	38	* Probe CPU types, I-/D-cache and TLB size etc. automatically
	39
	40	* Secondary cache support missing
	41
4a1f11b4 SK	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().
54b08efc	51
54b08efc DS	52	* centralize/share more CPU code of MIPS32, MIPS64 and XBurst
	53
	54	* support Qemu Malta