[U-Boot] [PATCH v2 2/6] spl: arm: implement SPL_CLEAR_BSS_F

[Simon Goldschmidt]

This implements the new option to clear BSS early in SPL for standard arm
and arm64 crt0.

BSS is cleared before calling board_init_f() and thus not cleared before
calling board_init_r() as it is not relocated in SPL.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
---

Changes in v2:
- add CONFIG_SPL_CLEAR_BSS_F implementation for arm64 also

 arch/arm/lib/crt0.S    | 22 ++++++++++++++++++++++
 arch/arm/lib/crt0_64.S | 14 ++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index fe312db690..b06e54e144 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -80,6 +80,26 @@ ENTRY(_main)
 	mov	r9, r0
 	bl	board_init_f_init_reserve
 
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_CLEAR_BSS_F)
+	ldr	r0, =__bss_start
+
+#ifdef CONFIG_USE_ARCH_MEMSET
+	ldr	r3, =__bss_end
+	mov	r1, #0x00000000		/* prepare zero to clear BSS */
+
+	subs	r2, r3, r0		/* r2 = memset len */
+	bl	memset
+#else
+	ldr	r1, =__bss_end
+	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
+#endif
+
 	mov	r0, #0
 	bl	board_init_f
 
@@ -124,6 +144,7 @@ here:
 	movne	sp, r0
 	movne	r9, r0
 # endif
+#if !defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_CLEAR_BSS_F)
 	ldr	r0, =__bss_start	/* this is auto-relocated! */
 
 #ifdef CONFIG_USE_ARCH_MEMSET
@@ -141,6 +162,7 @@ clbss_l:cmp	r0, r1			/* while not at end of BSS */
 	addlo	r0, r0, #4		/* move to next */
 	blo	clbss_l
 #endif
+#endif
 
 #if ! defined(CONFIG_SPL_BUILD)
 	bl coloured_LED_init
diff --git a/arch/arm/lib/crt0_64.S b/arch/arm/lib/crt0_64.S
index d6b632aa87..82f643f737 100644
--- a/arch/arm/lib/crt0_64.S
+++ b/arch/arm/lib/crt0_64.S
@@ -86,6 +86,18 @@ ENTRY(_main)
 	mov	x18, x0
 	bl	board_init_f_init_reserve
 
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_CLEAR_BSS_F)
+/*
+ * Clear BSS section
+ */
+	ldr	x0, =__bss_start
+	ldr	x1, =__bss_end
+clear_loop:
+	str	xzr, [x0], #8
+	cmp	x0, x1
+	b.lo	clear_loop
+#endif
+
 	mov	x0, #0
 	bl	board_init_f
 
@@ -136,6 +148,7 @@ relocation_return:
 	mov	sp, x0
 #endif
 
+#if !defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_CLEAR_BSS_F)
 /*
  * Clear BSS section
  */
@@ -145,6 +158,7 @@ clear_loop:
 	str	xzr, [x0], #8
 	cmp	x0, x1
 	b.lo	clear_loop
+#endif
 
 	/* call board_init_r(gd_t *id, ulong dest_addr) */
 	mov	x0, x18				/* gd_t */
-- 
2.17.1