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spl: Allow performing BSS init early before board_init_f()

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On some platform we have sufficient memory available early on to allow
setting up and using a basic BSS prior to entering board_init_f(). Doing
so can for example be used to carry state over to board_init_r() without
having to resort to extending U-Boot's global data structure.

To support such scenarios add a Kconfig option called CONFIG_SPL_EARLY_BSS
to allow moving the initialization of BSS prior to entering board_init_f(),
if enabled. Note that using this option usually should go along with using
CONFIG_SPL_SEPARATE_BSS and configuring BSS to be located in memory
actually available prior to board_init_f().

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
This commit is contained in:
Andreas Dannenberg 2019-06-04 17:55:45 -05:00 committed by Tom Rini
parent 70942db4dd
commit a5a5d997b4
2 changed files with 46 additions and 17 deletions
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53
arch/arm/lib/crt0.S
View file

@ -57,6 +57,33 @@
* For more information see 'Board Initialisation Flow in README.
*/
/*
* Macro for clearing BSS during SPL execution. Usually called during the
* relocation process for most boards before entering board_init_r(), but
* can also be done early before entering board_init_f() on plaforms that
* can afford it due to sufficient memory being available early.
*/
.macro SPL_CLEAR_BSS
ldr r0, =__bss_start /* this is auto-relocated! */
#ifdef CONFIG_USE_ARCH_MEMSET
ldr r3, =__bss_end /* this is auto-relocated! */
mov r1, #0x00000000 /* prepare zero to clear BSS */
subs r2, r3, r0 /* r2 = memset len */
bl memset
#else
ldr r1, =__bss_end /* this is auto-relocated! */
mov r2, #0x00000000 /* prepare zero to clear BSS */
clbss_l:cmp r0, r1 /* while not at end of BSS */
strlo r2, [r0] /* clear 32-bit BSS word */
addlo r0, r0, #4 /* move to next */
blo clbss_l
#endif
.endm
/*
* entry point of crt0 sequence
*/
@ -82,6 +109,10 @@ ENTRY(_main)
mov r9, r0
bl board_init_f_init_reserve
#if defined(CONFIG_SPL_EARLY_BSS)
SPL_CLEAR_BSS
#endif
mov r0, #0
bl board_init_f
@ -119,6 +150,11 @@ here:
bl c_runtime_cpu_setup /* we still call old routine here */
#endif
#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
#if !defined(CONFIG_SPL_EARLY_BSS)
SPL_CLEAR_BSS
#endif
# ifdef CONFIG_SPL_BUILD
/* Use a DRAM stack for the rest of SPL, if requested */
bl spl_relocate_stack_gd
@ -126,23 +162,6 @@ here:
movne sp, r0
movne r9, r0
# endif
ldr r0, =__bss_start /* this is auto-relocated! */
#ifdef CONFIG_USE_ARCH_MEMSET
ldr r3, =__bss_end /* this is auto-relocated! */
mov r1, #0x00000000 /* prepare zero to clear BSS */
subs r2, r3, r0 /* r2 = memset len */
bl memset
#else
ldr r1, =__bss_end /* this is auto-relocated! */
mov r2, #0x00000000 /* prepare zero to clear BSS */
clbss_l:cmp r0, r1 /* while not at end of BSS */
strlo r2, [r0] /* clear 32-bit BSS word */
addlo r0, r0, #4 /* move to next */
blo clbss_l
#endif
#if ! defined(CONFIG_SPL_BUILD)
bl coloured_LED_init

10
common/spl/Kconfig
View file

@ -248,6 +248,16 @@ config TPL_BANNER_PRINT
info. Disabling this option could be useful to reduce SPL boot time
(e.g. approx. 6 ms faster, when output on i.MX6 with 115200 baud).
config SPL_EARLY_BSS
depends on ARM && !ARM64
bool "Allows initializing BSS early before entering board_init_f"
help
On some platform we have sufficient memory available early on to
allow setting up and using a basic BSS prior to entering
board_init_f. Activating this option will also de-activate the
clearing of BSS during the SPL relocation process, thus allowing
to carry state from board_init_f to board_init_r by way of BSS.
config SPL_DISPLAY_PRINT
bool "Display a board-specific message in SPL"
help