feat: initial ACPI support

src/platform/acpi/timer.zig

@@ -0,0 +1,50 @@
+const b = @import("base");
+const std = @import("std");
+const acpi = b.pl.acpi;
+const ke = b.ke;
+const arch = @import("arch");
+
+var pm_timer: ke.TimeCounter = .{
+    .name = "ACPI",
+    .quality = 25,
+    .frequency = 3579545, // 3.579545 MHz
+    .read_count = read_timer,
+    .mask = std.math.maxInt(u24),
+    .p = 0,
+    .n = 0,
+};
+
+var timer_gas: acpi.Gas = undefined;
+
+pub fn init(fadt: *acpi.Fadt) linksection(b.init) void {
+    const fadt_rev = fadt.revision();
+
+    if (fadt.pm_tmr_len == 0 or fadt.pm_tmr_blk == 0) {
+        return;
+    }
+
+    if (fadt_rev >= 2 and fadt.x_pm_tmr_blk.address == 0) {
+        return;
+    }
+
+    timer_gas.address_space_id = .SystemIo;
+    timer_gas.address = fadt.pm_tmr_blk;
+    timer_gas.access_size = 3;
+    timer_gas.register_bit_width = 32;
+    timer_gas.register_bit_offset = 0;
+
+    if (fadt_rev >= 2) {
+        timer_gas = fadt.x_pm_tmr_blk;
+    }
+
+    // Indicates whether the timer is 32-bit
+    if (fadt.flags & (1 << 8) != 0) {
+        pm_timer.mask = std.math.maxInt(u32);
+    }
+
+    ke.time.register_source(&pm_timer);
+}
+
+fn read_timer() u64 {
+    return timer_gas.read();
+}