[PATCH 2/2] ARM: setup_c: avoid clearing BSS twice

[Sascha Hauer]

Add a bss_cleared variable that is set after the first call to
setup_c(). On subsequent calls, the BSS clear is skipped to avoid
wiping already-initialized data.

Co-Authored-By: Claude Opus 4.6 <noreply at anthropic.com>
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 arch/arm/cpu/common.c    |  2 ++
 arch/arm/cpu/setupc_32.S | 10 +++++++++-
 arch/arm/cpu/setupc_64.S | 10 ++++++++--
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index e86c89f808..40742894c2 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -77,6 +77,8 @@ int __pure cpu_architecture(void)
 }
 #endif
 
+int bss_cleared;
+
 extern int __boot_cpu_mode;
 
 int boot_cpu_mode(void)
diff --git a/arch/arm/cpu/setupc_32.S b/arch/arm/cpu/setupc_32.S
index c2c3f97528..d923a8f621 100644
--- a/arch/arm/cpu/setupc_32.S
+++ b/arch/arm/cpu/setupc_32.S
@@ -7,16 +7,24 @@
 .section .text.setupc
 
 /*
- * setup_c: clear bss
+ * setup_c: clear bss if not yet done
  */
 ENTRY(setup_c)
+	ldr	r0, =bss_cleared
+	ldr	r1, [r0]
+	cmp	r1, #0
+	bne	1f			/* skip if already done */
 	mov	r4, lr
 	ldr	r0, =__bss_start
 	mov	r1, #0
 	ldr	r2, =__bss_stop
 	sub	r2, r2, r0
 	bl	__memset		/* clear bss */
+	ldr	r0, =bss_cleared
+	mov	r1, #1
+	str	r1, [r0]		/* mark bss cleared */
 	ret	r4
+1:	ret	lr
 ENDPROC(setup_c)
 
 /*
diff --git a/arch/arm/cpu/setupc_64.S b/arch/arm/cpu/setupc_64.S
index fd95187a04..8262deb512 100644
--- a/arch/arm/cpu/setupc_64.S
+++ b/arch/arm/cpu/setupc_64.S
@@ -7,17 +7,23 @@
 .section .text.setupc
 
 /*
- * setup_c: clear bss
+ * setup_c: clear bss if not yet done
  */
 ENTRY(setup_c)
+	adr_l	x0, bss_cleared
+	ldr	w1, [x0]
+	cbnz	w1, 1f			/* skip if already done */
 	mov	x15, x30
 	adr_l	x0, __bss_start
 	mov	x1, #0
 	adr_l	x2, __bss_stop
 	sub	x2, x2, x0
 	bl	__memset		/* clear bss */
+	adr_l	x0, bss_cleared
+	mov	w1, #1
+	str	w1, [x0]		/* mark bss cleared */
 	mov	x30, x15
-	ret
+1:	ret
 ENDPROC(setup_c)
 
 /*

-- 
2.47.3