sylveos

commit 0654143545f9d3d258d0adbdee7d70aa1c817bca
parent 1441f5976f96cf2dc1f6e1390fd1b4b0cd4c4565
Author: Sylvia Ivory <git@sivory.net>
Date:   Thu, 15 Jan 2026 17:37:19 -0800

Start memory operation rework

Diffstat:
D
src/barrier.zig
 | 
19
-------------------
A
src/mem.zig
 | 
62
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 62 insertions(+), 19 deletions(-)
diff --git a/src/barrier.zig b/src/barrier.zig
@@ -1,19 +0,0 @@
-// https://developer.arm.com/documentation/ddi0333/h/system-control-coprocessor/system-control-processor-registers/c7--cache-operations
-
-released: bool,
-
-pub fn obtain() @This() {
-    asm volatile ("MCR p15, 0, r0, c7, c10, 4");
-
-    return .{ .released = false };
-}
-
-pub fn release(barrier: *@This()) void {
-    if (barrier.released) @panic("attempt to release already released barrier");
-    barrier.released = true;
-    asm volatile ("MCR p15, 0, r0, c7, c10, 5");
-}
-
-pub fn active(barrier: *@This()) void {
-    return !barrier.released;
-}
diff --git a/src/mem.zig b/src/mem.zig
@@ -0,0 +1,62 @@
+// Forces all outstanding explicit memory transactions to complete before executing
+// another **instruction**. Other instructions can execute out of order
+inline fn dsb() void {
+    asm volatile ("mcr p15, 0, %[reg], c7, c10, 5"
+        :
+        : [reg] "r" (0),
+    );
+}
+// Forces all outstanding explicit memory transactions to complete before executing
+// another **memory transaction**. No instruction can execute until this is complete
+inline fn dmb() void {
+    asm volatile ("mcr p15, 0, %[reg], c7, c10, 4"
+        :
+        : [reg] "r" (0),
+    );
+}
+
+const BarrierKind = enum {
+    Strict,
+    Weak,
+};
+
+const Operation = enum {
+    Read,
+    Write,
+    General,
+};
+
+pub inline fn barrier(op: Operation) void {
+    switch (op) {
+        .Write => dmb(),
+        .General | .Read => dsb(),
+    }
+}
+
+pub inline fn put_u32(address: *u32, value: u32) void {
+    asm volatile ("str %[value], [%[address]]"
+        :
+        : [value] "r" (value),
+          [address] "=r" (address),
+    );
+}
+
+pub inline fn put_u32_barrier(
+    address: *u32,
+    value: u32,
+) void {
+    put_u32(address, value);
+    barrier(.Write);
+}
+
+pub inline fn get_u32(address: *u32) u32 {
+    return asm volatile ("str %[result], [%[address]]"
+        : [result] "r" (-> u32),
+        : [address] "=r" (address),
+    );
+}
+
+pub inline fn get_u32_barrier(address: *u32) u32 {
+    barrier(.Read);
+    return get_u32(address);
+}