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 documented in the README.
Signed-off-by: Simon Glass sjg@chromium.org For version 1: Acked-by: Albert ARIBAUD albert.u.boot@aribaud.net Reviewed-by: Stefan Roese sr@denx.de Tested-by: Bo Shen voice.shen@atmel.com Acked-by: Bo Shen voice.shen@atmel.com Acked-by: Heiko Schocher hs@denx.de Tested-by: Heiko Schocher hs@denx.de ---
Changes in v6: None Changes in v5: - Rebase to master
Changes in v4: - Adjust README to mention that lowlevel_init() should have no stack
Changes in v3: None Changes in v2: - Move docs to top-level README file and expand them to cover U-Boot proper - Add Kconfig settings
Kconfig | 18 ++++++++++++++ README | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++ arch/arm/lib/crt0.S | 13 +++++++--- common/spl/spl.c | 35 +++++++++++++++++++++++++++ 4 files changed, 132 insertions(+), 3 deletions(-)
diff --git a/Kconfig b/Kconfig index 91a0618..8de731d 100644 --- a/Kconfig +++ b/Kconfig @@ -96,6 +96,24 @@ config SPL help If you want to build SPL as well as the normal image, say Y.
+config CONFIG_SPL_STACK_R + depends on SPL + bool "Enable SDRAM location for SPL stack" + help + SPL starts off execution in SRAM and thus typically has only a small + stack available. Since SPL sets up DRAM while in its board_init_f() + function, it is possible for the stack to move there before + board_init_r() is reached. This option enables a special SDRAM + location for the SPL stack. U-Boot SPL switches to this after + board_init_f() completes, and before board_init_r() starts. + +config CONFIG_SPL_STACK_R_ADDR + depends on CONFIG_SPL_STACK_R + hex "SDRAM location for SPL stack" + help + Specify the address in SDRAM for the SPL stack. This will be set up + before board_init_r() is called. + config TPL bool depends on SPL && SUPPORT_TPL diff --git a/README b/README index febefb5..3547ead 100644 --- a/README +++ b/README @@ -273,6 +273,75 @@ run some of U-Boot's tests. See board/sandbox/README.sandbox for more details.
+Board Initialisation Flow: +-------------------------- + +This is the intended start-up flow for boards. This should apply for both +SPL and U-Boot proper (i.e. they both follow the same rules). At present SPL +mostly uses a separate code path, but the funtion names and roles of each +function are the same. Some boards or architectures may not conform to this. +At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this. + +Execution starts with start.S with three functions called during init after +that. The purpose and limitations of each is described below. + +lowlevel_init(): + - purpose: essential init to permit execution to reach board_init_f() + - no global_data or BSS + - there is no stack (ARMv7 may have one but it will soon be removed) + - 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 + - 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) + +Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at +this point the stack and global_data are relocated to below +CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of +memory. + +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 defining CONFIG_SPL_BOARD_INIT and then supplying a + spl_board_init() function containing this call + - loads U-Boot or (in falcon mode) Linux + + + Configuration Options: ----------------------
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S index 22df3e5..7939ced 100644 --- a/arch/arm/lib/crt0.S +++ b/arch/arm/lib/crt0.S @@ -113,7 +113,14 @@ here: /* Set up final (full) environment */
bl c_runtime_cpu_setup /* we still call old routine here */ - +#endif +#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK) +# ifdef CONFIG_SPL_BUILD + /* Use a DRAM stack for the rest of SPL, if requested */ + bl spl_relocate_stack_gd + cmp r0, #0 + movne sp, r0 +# endif ldr r0, =__bss_start /* this is auto-relocated! */ ldr r1, =__bss_end /* this is auto-relocated! */
@@ -124,9 +131,10 @@ clbss_l:cmp r0, r1 /* while not at end of BSS */ addlo r0, r0, #4 /* move to next */ blo clbss_l
+#if ! defined(CONFIG_SPL_BUILD) bl coloured_LED_init bl red_led_on - +#endif /* call board_init_r(gd_t *id, ulong dest_addr) */ mov r0, r9 /* gd_t */ ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ @@ -134,7 +142,6 @@ clbss_l:cmp r0, r1 /* while not at end of BSS */ ldr pc, =board_init_r /* this is auto-relocated! */
/* we should not return here. */ - #endif
ENDPROC(_main) diff --git a/common/spl/spl.c b/common/spl/spl.c index ded0f30..cd75bbc 100644 --- a/common/spl/spl.c +++ b/common/spl/spl.c @@ -281,3 +281,38 @@ void preloader_console_init(void) spl_display_print(); #endif } + +/** + * spl_relocate_stack_gd() - Relocate stack ready for board_init_r() execution + * + * Sometimes board_init_f() runs with a stack in SRAM but we want to use SDRAM + * for the main board_init_r() execution. This is typically because we need + * more stack space for things like the MMC sub-system. + * + * This function calculates the stack position, copies the global_data into + * place and returns the new stack position. The caller is responsible for + * setting up the sp register. + * + * @return new stack location, or 0 to use the same stack + */ +ulong spl_relocate_stack_gd(void) +{ +#ifdef CONFIG_SPL_STACK_R + gd_t *new_gd; + ulong ptr; + + /* Get stack position: use 8-byte alignment for ABI compliance */ + ptr = CONFIG_SPL_STACK_R - sizeof(gd_t); + ptr &= ~7; + new_gd = (gd_t *)ptr; + memcpy(new_gd, (void *)gd, sizeof(gd_t)); + gd = new_gd; + + /* Clear the BSS. */ + memset(__bss_start, 0, __bss_end - __bss_start); + + return ptr; +#else + return 0; +#endif +}