From ea75413df032b5c33e6207531e3c24b99bfb41e8 Mon Sep 17 00:00:00 2001
From: Berkus Decker <berkus+github@metta.systems>
Date: Tue, 27 Oct 2020 11:34:36 +0200
Subject: [PATCH] Add looping/delay helpers

---
 nucleus/src/arch/aarch64/mod.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/nucleus/src/arch/aarch64/mod.rs b/nucleus/src/arch/aarch64/mod.rs
index 24965ad..2435c9e 100644
--- a/nucleus/src/arch/aarch64/mod.rs
+++ b/nucleus/src/arch/aarch64/mod.rs
@@ -5,6 +5,8 @@
 
 //! Implementation of aarch64 kernel functions.
 
+use cortex_a::asm;
+
 mod boot;
 pub mod memory;
 pub mod traps;
@@ -13,6 +15,25 @@ pub mod traps;
 #[inline]
 pub fn endless_sleep() -> ! {
     loop {
-        cortex_a::asm::wfe();
+        asm::wfe();
+    }
+}
+
+/// Loop for a given number of `nop` instructions.
+#[inline]
+pub fn loop_delay(rounds: u32) {
+    for _ in 0..rounds {
+        asm::nop();
+    }
+}
+
+/// Loop until a passed function returns `true`.
+#[inline]
+pub fn loop_until<F: Fn() -> bool>(f: F) {
+    loop {
+        if f() {
+            break;
+        }
+        asm::nop();
     }
 }