On 18.01.2015 19:55, Simon Glass wrote:
At present SPL uses a single stack, either CONFIG_SPL_STACK or CONFIG_SYS_INIT_SP_ADDR. Since some SPL features (such as MMC and environment) require a lot of stack, some boards set CONFIG_SPL_STACK to point into SDRAM. They then set up SDRAM very early, before board_init_f(), so that the larger stack can be used.
This is an abuse of lowlevel_init(). That function should only be used for essential start-up code which cannot be delayed. An example of a valid use is when only part of the SPL code is visible/executable, and the SoC must be set up so that board_init_f() can be reached. It should not be used for SDRAM init, console init, etc.
Add a CONFIG_SPL_STACK_R option, which allows the stack to be moved to a new address before board_init_r() is called in SPL.
The expected SPL flow (for CONFIG_SPL_FRAMEWORK) is now:
Execution starts with start.S. Two main functions can be provided by the board implementation. The purpose and limitations of each is described below. After that, the common board_init_r() is called to perform the SPL task.
lowlevel_init():
- purpose: essential init to permit execution to reach board_init_f()
- no global_data, but there is a stack
- must not set up SDRAM or use console
- must only do the bare minimum to allow execution to continue to board_init_f()
- this is almost never needed
- return normally from this function
board_init_f():
- purpose: set up the machine ready for running board_init_r(): i.e. SDRAM and serial UART
- global_data is available
- preloader_console_init() can be called here in extremis
- stack is in SRAM
- 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)
Here the BSS is cleared. If CONFIG_SPL_STACK_R is defined, then at this point the stack and global_data are relocated to below that address.
board_init_r():
- purpose: main execution, common code
- global_data is available
- SDRAM is available
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and points into SDRAM
- preloader_console_init() can be called here - typically this is done by defining CONFIG_SPL_BOARD_INIT and then supplying a spl_board_init() function containing this call
- loads U-Boot or (in falcon mode) Linux
Note: This patch is intended to apply over the top of Tom's SPL changes and this series:
https://patchwork.ozlabs.org/patch/423785/
Signed-off-by: Simon Glass sjg@chromium.org
Reviewed-by: Stefan Roese sr@denx.de
Thanks, Stefan