spl: Allow performing BSS init early before board_init_f()
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>
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index 30fba20..c74641d 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -58,6 +58,33 @@
*/
/*
+ * 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 @@
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 @@
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 @@
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