arm: spl: Allow board_init_r() to run with a larger stack
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> Signed-off-by: Tom Rini <trini@konsulko.com>
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Simon Glass
Tom Rini
parent
bdfb34167f
commit
db910353a1
18
Kconfig
18
Kconfig
@ -96,6 +96,24 @@ config SPL
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help
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If you want to build SPL as well as the normal image, say Y.
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config SPL_STACK_R
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depends on SPL
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bool "Enable SDRAM location for SPL stack"
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help
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SPL starts off execution in SRAM and thus typically has only a small
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stack available. Since SPL sets up DRAM while in its board_init_f()
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function, it is possible for the stack to move there before
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board_init_r() is reached. This option enables a special SDRAM
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location for the SPL stack. U-Boot SPL switches to this after
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board_init_f() completes, and before board_init_r() starts.
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config SPL_STACK_R_ADDR
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depends on SPL_STACK_R
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hex "SDRAM location for SPL stack"
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help
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Specify the address in SDRAM for the SPL stack. This will be set up
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before board_init_r() is called.
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config TPL
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bool
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depends on SPL && SUPPORT_TPL
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69
README
69
README
@ -273,6 +273,75 @@ run some of U-Boot's tests.
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See board/sandbox/README.sandbox for more details.
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Board Initialisation Flow:
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--------------------------
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This is the intended start-up flow for boards. This should apply for both
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SPL and U-Boot proper (i.e. they both follow the same rules). At present SPL
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mostly uses a separate code path, but the funtion names and roles of each
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function are the same. Some boards or architectures may not conform to this.
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At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this.
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Execution starts with start.S with three functions called during init after
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that. The purpose and limitations of each is described below.
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lowlevel_init():
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- purpose: essential init to permit execution to reach board_init_f()
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- no global_data or BSS
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- there is no stack (ARMv7 may have one but it will soon be removed)
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- must not set up SDRAM or use console
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- must only do the bare minimum to allow execution to continue to
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board_init_f()
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- this is almost never needed
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- return normally from this function
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board_init_f():
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- purpose: set up the machine ready for running board_init_r():
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i.e. SDRAM and serial UART
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- global_data is available
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- stack is in SRAM
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- BSS is not available, so you cannot use global/static variables,
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only stack variables and global_data
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Non-SPL-specific notes:
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- dram_init() is called to set up DRAM. If already done in SPL this
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can do nothing
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SPL-specific notes:
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- you can override the entire board_init_f() function with your own
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version as needed.
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- preloader_console_init() can be called here in extremis
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- should set up SDRAM, and anything needed to make the UART work
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- these is no need to clear BSS, it will be done by crt0.S
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- must return normally from this function (don't call board_init_r()
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directly)
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Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
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this point the stack and global_data are relocated to below
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CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
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memory.
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board_init_r():
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- purpose: main execution, common code
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- global_data is available
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- SDRAM is available
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- BSS is available, all static/global variables can be used
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- execution eventually continues to main_loop()
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Non-SPL-specific notes:
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- U-Boot is relocated to the top of memory and is now running from
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there.
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SPL-specific notes:
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- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
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CONFIG_SPL_STACK_R_ADDR points into SDRAM
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- preloader_console_init() can be called here - typically this is
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done by defining CONFIG_SPL_BOARD_INIT and then supplying a
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spl_board_init() function containing this call
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- loads U-Boot or (in falcon mode) Linux
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Configuration Options:
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----------------------
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@ -113,7 +113,14 @@ here:
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/* Set up final (full) environment */
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bl c_runtime_cpu_setup /* we still call old routine here */
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#endif
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#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
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# ifdef CONFIG_SPL_BUILD
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/* Use a DRAM stack for the rest of SPL, if requested */
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bl spl_relocate_stack_gd
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cmp r0, #0
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movne sp, r0
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# endif
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ldr r0, =__bss_start /* this is auto-relocated! */
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ldr r1, =__bss_end /* this is auto-relocated! */
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@ -124,9 +131,10 @@ clbss_l:cmp r0, r1 /* while not at end of BSS */
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addlo r0, r0, #4 /* move to next */
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blo clbss_l
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#if ! defined(CONFIG_SPL_BUILD)
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bl coloured_LED_init
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bl red_led_on
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#endif
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/* call board_init_r(gd_t *id, ulong dest_addr) */
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mov r0, r9 /* gd_t */
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ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
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@ -134,7 +142,6 @@ clbss_l:cmp r0, r1 /* while not at end of BSS */
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ldr pc, =board_init_r /* this is auto-relocated! */
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/* we should not return here. */
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#endif
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ENDPROC(_main)
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@ -281,3 +281,38 @@ void preloader_console_init(void)
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spl_display_print();
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#endif
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}
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/**
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* spl_relocate_stack_gd() - Relocate stack ready for board_init_r() execution
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*
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* Sometimes board_init_f() runs with a stack in SRAM but we want to use SDRAM
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* for the main board_init_r() execution. This is typically because we need
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* more stack space for things like the MMC sub-system.
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*
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* This function calculates the stack position, copies the global_data into
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* place and returns the new stack position. The caller is responsible for
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* setting up the sp register.
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*
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* @return new stack location, or 0 to use the same stack
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*/
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ulong spl_relocate_stack_gd(void)
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{
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#ifdef CONFIG_SPL_STACK_R
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gd_t *new_gd;
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ulong ptr;
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/* Get stack position: use 8-byte alignment for ABI compliance */
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ptr = CONFIG_SPL_STACK_R - sizeof(gd_t);
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ptr &= ~7;
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new_gd = (gd_t *)ptr;
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memcpy(new_gd, (void *)gd, sizeof(gd_t));
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gd = new_gd;
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/* Clear the BSS. */
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memset(__bss_start, 0, __bss_end - __bss_start);
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return ptr;
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#else
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return 0;
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#endif
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}
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