workaround for compiler bug where volatile is not propagated over a field access (#57)

src/hal/resets.zig

@@ -44,18 +44,23 @@ pub fn reset(mask: Mask) void {
     while ((RESETS.RESET_DONE.raw & raw_mask) != raw_mask) {}
 }
 
-pub fn reset_block(mask: Mask) void {
+pub inline fn reset_block(mask: Mask) void {
     hw.set_alias_raw(&RESETS.RESET).* = @bitCast(u32, mask);
 }
 
-pub fn unreset_block(mask: Mask) void {
+pub inline fn unreset_block(mask: Mask) void {
     hw.clear_alias_raw(&RESETS.RESET).* = @bitCast(u32, mask);
 }
 
 pub fn unreset_block_wait(mask: Mask) void {
     const raw_mask = @bitCast(u32, mask);
     hw.clear_alias_raw(&RESETS.RESET).* = raw_mask;
-    while (RESETS.RESET_DONE.raw & raw_mask != raw_mask) {}
+
+    // have to bitcast after a read() instead of `RESETS.RESET_DONE.raw` due to
+    // some optimization bug. While loops will not be optimzed away if the
+    // condition has side effects like dereferencing a volatile pointer.
+    // It seems that volatile is not propagating correctly.
+    while (@bitCast(u32, RESETS.RESET_DONE.read()) & raw_mask != raw_mask) {}
 }
 
 pub const masks = struct {