Commit db910353 authored by Simon Glass's avatar Simon Glass Committed by Tom Rini

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: default avatarSimon Glass <>
For version 1:
Acked-by: default avatarAlbert ARIBAUD <>
Reviewed-by: default avatarStefan Roese <>
Tested-by: default avatarBo Shen <>
Acked-by: default avatarBo Shen <>
Acked-by: default avatarHeiko Schocher <>
Tested-by: default avatarHeiko Schocher <>
Signed-off-by: default avatarTom Rini <>
parent bdfb3416
......@@ -96,6 +96,24 @@ config SPL
If you want to build SPL as well as the normal image, say Y.
config SPL_STACK_R
depends on SPL
bool "Enable SDRAM location for SPL stack"
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.
depends on SPL_STACK_R
hex "SDRAM location for SPL stack"
Specify the address in SDRAM for the SPL stack. This will be set up
before board_init_r() is called.
config TPL
depends on SPL && SUPPORT_TPL
......@@ -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.
- 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
- this is almost never needed
- return normally from this function
- 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()
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
- 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
SPL-specific notes:
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
- 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:
......@@ -113,7 +113,14 @@ here:
/* Set up final (full) environment */
bl c_runtime_cpu_setup /* we still call old routine here */
/* 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
/* 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. */
......@@ -281,3 +281,38 @@ void preloader_console_init(void)
* 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)
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;
return 0;
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