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commit f59510ec62802cfdd4409ca2a8d9bebce7fe6cfa
Author: hujun5 <huj...@xiaomi.com>
AuthorDate: Wed Apr 16 10:30:27 2025 +0800
armv[7/8]-r: add ARM_BUSY_WAIT
On a system with multiple CPU cores, when the system is powered on,
multiple cores may start running simultaneously. In this case, software
is required to handle the startup logic for multi-core synchronization.
One approach is to use global variables.
however, the global variable region may not have been initialized yet.
In such scenarios, we can use a busywait flag to
implement the synchronization strategy.
Signed-off-by: hujun5 <huj...@xiaomi.com>
---
arch/arm/src/armv7-r/arm_head.S | 19 +++++++++++++++++++
arch/arm/src/armv8-r/arm_head.S | 17 +++++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/arch/arm/src/armv7-r/arm_head.S b/arch/arm/src/armv7-r/arm_head.S
index 0ec9a7d306..95ea23456f 100644
--- a/arch/arm/src/armv7-r/arm_head.S
+++ b/arch/arm/src/armv7-r/arm_head.S
@@ -134,7 +134,17 @@ __start:
and r0, r0, #0x3
cmp r0, #0
beq __cpu0_start
+
+#ifdef CONFIG_ARM_BUSY_WAIT
+ ldr r2, =CONFIG_ARM_BUSY_WAIT_FLAG_ADDR
+1:
+ ldr r1, [r2, #0]
+ cmp r1, #0
+ beq 1b
+#else
wfe
+#endif
+
cmp r0, #1
beq __cpu1_start
# if CONFIG_SMP_NCPUS > 2
@@ -395,6 +405,15 @@ __cpu0_start:
b arm_boot
+ /* finish busy wait */
+
+#if defined(CONFIG_ARM_BUSY_WAIT) && defined(CONFIG_SMP)
+ ldr r0, =CONFIG_ARM_BUSY_WAIT_FLAG_ADDR
+ mov r1, #1
+ str r1, [r0]
+ dsb sy
+#endif
+
/* .text Data */
.Lstackpointer:
diff --git a/arch/arm/src/armv8-r/arm_head.S b/arch/arm/src/armv8-r/arm_head.S
index 2caded5446..6d3eec5ff4 100644
--- a/arch/arm/src/armv8-r/arm_head.S
+++ b/arch/arm/src/armv8-r/arm_head.S
@@ -142,7 +142,17 @@ __start:
cmp r0, #0
#if defined(CONFIG_SMP) && CONFIG_SMP_NCPUS > 1
beq __cpu0_start
+
+#ifdef CONFIG_ARM_BUSY_WAIT
+ ldr r2, =CONFIG_ARM_BUSY_WAIT_FLAG_ADDR
+1:
+ ldr r1, [r2, #0]
+ cmp r1, #0
+ beq 1b
+#else
wfe
+#endif
+
cmp r0, #1
beq __cpu1_start
# if CONFIG_SMP_NCPUS > 2
@@ -247,6 +257,13 @@ __cpu0_start:
mov lr, #0 /* LR = return address
(none) */
b nx_start /* Branch to nx_start */
+#if defined(CONFIG_ARM_BUSY_WAIT) && defined(CONFIG_SMP)
+ ldr r0, =CONFIG_ARM_BUSY_WAIT_FLAG_ADDR
+ mov r1, #1
+ str r1, [r0]
+ dsb sy
+#endif
+
/* .text Data */
.Lstackpointer:
