From 38852ef7c7fee9ee7019fd734994294a3c74ab0f Mon Sep 17 00:00:00 2001
From: Simon Renblad <srenblad@m-labs.hk>
Date: Mon, 6 Jan 2025 11:17:13 +0800
Subject: [PATCH] add isb after cpacr update

---
 libcortex_a9/src/fpu.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libcortex_a9/src/fpu.rs b/libcortex_a9/src/fpu.rs
index c4dd568..6daa144 100644
--- a/libcortex_a9/src/fpu.rs
+++ b/libcortex_a9/src/fpu.rs
@@ -1,12 +1,14 @@
 use core::arch::asm;
 /// Enable FPU in the current core.
+/// You must execute an ISB immediately after an update of the CPACR.
+/// https://developer.arm.com/documentation/ddi0388/i/system-control/register-descriptions/coprocessor-access-control-register
 pub fn enable_fpu() {
     unsafe {
         asm!("
             mrc p15, 0, r1, c1, c0, 2
             orr r1, r1, (0b1111<<20)
             mcr p15, 0, r1, c1, c0, 2
-
+            isb
             vmrs r1, fpexc
             orr r1, r1, (1<<30)
             vmsr fpexc, r1