From 8ea47b72f8fabe57a0762ca79f04101ae4cd12d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Gr=C3=A9goire?= <loic@gregoire.dev>
Date: Wed, 15 Apr 2026 20:40:57 -0400
Subject: [PATCH] fix(acpi): ensure proper GAS for timer

---
 src/platform/acpi/root.zig  | 16 ++++++++--------
 src/platform/acpi/timer.zig |  4 ++++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/platform/acpi/root.zig b/src/platform/acpi/root.zig
index 14e7956..6f2f538 100644
--- a/src/platform/acpi/root.zig
+++ b/src/platform/acpi/root.zig
@@ -337,21 +337,21 @@ pub fn init(boot_info: *pl.BootInfo) linksection(b.init) void {
 
     enumerate_tables();
 
-    const fadt = find_table(fadt_signature);
-
-    if (fadt) |f| {
-        const fadt_struct: *Fadt = @ptrCast(f);
-        timer.init(fadt_struct);
-    }
-
+    // Try getting the HPET first so we don't initialize
+    // the legacy timer if we have a better option.
     const hpet_t = find_table(hpet_signature);
     if (hpet_t) |h| {
         const hpet_struct: *HpetTable = @ptrCast(h);
         hpet.init(hpet_struct);
     }
 
-    const madt_t = find_table(madt_signature);
+    const fadt = find_table(fadt_signature);
+    if (fadt) |f| {
+        const fadt_struct: *Fadt = @ptrCast(f);
+        timer.init(fadt_struct);
+    }
 
+    const madt_t = find_table(madt_signature);
     if (madt_t) |m| {
         madt.madt_ptr = @ptrCast(m);
     }
diff --git a/src/platform/acpi/timer.zig b/src/platform/acpi/timer.zig
index 1ea0bbd..089ceee 100644
--- a/src/platform/acpi/timer.zig
+++ b/src/platform/acpi/timer.zig
@@ -37,6 +37,10 @@ pub fn init(fadt: *acpi.Fadt) linksection(b.init) void {
         timer_gas = fadt.x_pm_tmr_blk;
     }
 
+    if (timer_gas.access_size == 0) {
+        timer_gas.access_size = 3;
+    }
+
     // Indicates whether the timer is 32-bit
     if (fadt.flags & (1 << 8) != 0) {
         pm_timer.mask = std.math.maxInt(u32);