Hi Guys,
I try to understand why we need to do the relocate in U-Boot.
From the document README/crt0.S, I think the relocation feature comes
from some SoC have limited SRAM whose size is enough to load the whole
U-Boot, but not enough to run all the drivers.
I don't know how many SoCs/Archs still must use this feature, but
I'm sure all
Rockchip SoCs do not need this feature in both SPL and proper U-Boot,
because rockchip using SPL always running in SRAM to init DDR SDRAM,
and after DRAM available always running U-Boot in DRAM.
There is a CONFIG_SPL_SKIP_RELOCATE for SPL to skip the relocate,
can we have another CONFIG_SKIP_RELOCATE for U-Boot proper?
Here is the document from README:
board_init_f():
- purpose: set up the machine ready for running board_init_r():
i.e. SDRAM and serial UART
- global_data is available
- stack is in SRAM
- BSS is not available, so you cannot use global/static variables,
only stack variables and global_data
Non-SPL-specific notes:
- dram_init() is called to set up DRAM. If already done in SPL
this
can do nothing
SPL-specific notes:
- you can override the entire board_init_f() function with your own
version as needed.
- preloader_console_init() can be called here in extremis
- should set up SDRAM, and anything needed to make the UART work
- these is no need to clear BSS, it will be done by crt0.S
- must return normally from this function (don't call
board_init_r()
directly)
board_init_r():
- purpose: main execution, common code
- global_data is available
- SDRAM is available
- BSS is available, all static/global variables can be used
- execution eventually continues to main_loop()
Non-SPL-specific notes:
- U-Boot is relocated to the top of memory and is now running from
there.
SPL-specific notes:
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is
defined and
CONFIG_SPL_STACK_R_ADDR points into SDRAM
- preloader_console_init() can be called here - typically this is
done by selecting CONFIG_SPL_BOARD_INIT and then
supplying a
spl_board_init() function containing this call
- loads U-Boot or (in falcon mode) Linux
Thanks,
- Kever
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