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reset doc added for ARM

This commit is contained in:
Juergen Beisert 2007-10-19 16:35:25 +02:00
parent 578433a5a8
commit be65b56a89
1 changed files with 24 additions and 0 deletions
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arch/arm/mach-arm.dox
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@ -6,4 +6,28 @@
FIXME
@par What's happens when the reset signal is gone
@note Code running immediately after reset runs at an address it is not linked
to: "runtime address != link address". You should only use branches and
do not refer to fixed data. This implies the use of assembler code only.
The ARM CPU starts at lable <reset> in one of the corresponding start-*.S
files. After some basic hardware setup it can call a function
<arch_init_lowlevel> if not disabled. This call is intended to give all
developers a chance to use a standard reset vector file, but also do some
special things required only on their specific CPU.
After handling some MMU related things <board_init_lowlevel> can be called (if
not disabled). This is a board specific function for SDRAM setup for example.
As its board specific, your can do whatever you need to bring your board up.
When <board_init_lowlevel> returns it will be assumed there is now a working
RAM that can be used for all further steps.
Next step is relocation of UBoot itself. It gets copied to RAM and the last
assembler instruction is a jump into <start_uboot>. This target address is
the first C instruction in UBoot. At this point of time:
"runtime address == link address".
*/