Hello Simon, On Sun, 18 Jan 2015 11:55:36 -0700, Simon Glass <s...@chromium.org> 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
Seems to me that now SPL and non-SPL boot sequences are mostly similar in the name, order and purpose of the functions called (which is a good thing!) so maybe this sequence should be described in a single document rather than in doc/README.SPL? Just opening the discussion; I have no strong opinion on this. > 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 <s...@chromium.org> > --- Acked-by: Albert ARIBAUD <albert.u.boot@aribaudnet> Amicalement, -- Albert. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
