sylveos

commit 1f00add3f80396de50bca2547372a9300a1ff027
parent fa0aa92896c22f40ce2c3539343a662a2d76aabb
Author: Sylvia Ivory <git@sivory.net>
Date:   Tue, 13 Jan 2026 20:03:11 -0800

Add system timer

Diffstat:
M
src/sys-timer.zig
 | 
41
++++++++++++++++++++++++++++++++++++-----

1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/src/sys-timer.zig b/src/sys-timer.zig
@@ -1,11 +1,42 @@
 const std = @import("std");
+const barrier = @import("barrier.zig");
 
 const BASE_ADDR: u32 = 0x2000_3000;
 
-const STATUS: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x00);
+// const STATUS: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x00);
 const COUNTER_LOWER: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x04);
 const COUNTER_UPPER: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x08);
-const COMPARE_0: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x0C);
-const COMPARE_1: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x10);
-const COMPARE_2: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x14);
-const COMPARE_3: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x18);
+// const COMPARE_0: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x0C);
+// const COMPARE_1: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x10);
+// const COMPARE_2: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x14);
+// const COMPARE_3: *volatile u32 = @ptrFromInt(BASE_ADDR + 0x18);
+
+pub fn current_count() u64 {
+    const b = barrier.obtain();
+    defer b.release();
+
+    const upper = COUNTER_UPPER.*;
+    const lower = COUNTER_LOWER.*;
+    const extended: u64 = @intCast(upper);
+
+    return (extended << 32) | lower;
+}
+
+// Busy delay
+// Not the best way to delay *but* a proper delay
+// requires *a lot* more code
+pub fn delay(us: u64) void {
+    const start = current_count();
+    while (true) {
+        const current = current_count();
+        if ((current - start) >= us) return;
+    }
+}
+
+pub fn delay_ms(ms: u64) void {
+    delay(ms * 1000);
+}
+
+pub fn delay_s(s: u64) void {
+    delay_ms(s * 1000);
+}