From 5b5c08a1054d4353b8b4d8f7deb5d25f6ff7e361 Mon Sep 17 00:00:00 2001
From: mintsuki <mintsuki@protonmail.com>
Date: Tue, 25 Feb 2025 04:07:30 +0100
Subject: [PATCH] kern: Initial support for the HPET

---
 kernel/main.v                          | 15 ++++++
 kernel/modules/acpi/acpi.v             | 12 -----
 kernel/modules/{acpi => uacpi}/uacpi.v | 12 ++---
 kernel/modules/x86/hpet/hpet.v         | 66 ++++++++++++++++++++++++++
 4 files changed, 85 insertions(+), 20 deletions(-)
 rename kernel/modules/{acpi => uacpi}/uacpi.v (97%)
 create mode 100644 kernel/modules/x86/hpet/hpet.v

diff --git a/kernel/main.v b/kernel/main.v
index f6a3284b9..ff42b1c2c 100644
--- a/kernel/main.v
+++ b/kernel/main.v
@@ -9,6 +9,7 @@ import lib.stubs
 import memory
 import term
 import acpi
+import uacpi
 import x86.gdt
 import x86.idt
 import x86.isr
@@ -35,6 +36,7 @@ import dev.mouse
 import syscall.table
 import socket
 import time
+import x86.hpet
 import limine
 
 #include <symbols.h>
@@ -120,6 +122,19 @@ pub fn kmain() {
 
 	// ACPI init
 	acpi.initialise()
+	hpet.initialise()
+
+	mut uacpi_status := uacpi.UACPIStatus.ok
+
+	uacpi_status = C.uacpi_initialize(0)
+	if uacpi_status != uacpi.UACPIStatus.ok {
+		panic('uacpi_initialize(): ${C.uacpi_status_to_string(uacpi_status)}')
+	}
+
+	uacpi_status = C.uacpi_namespace_load()
+	if uacpi_status != uacpi.UACPIStatus.ok {
+		panic('uacpi_namespace_load(): ${C.uacpi_status_to_string(uacpi_status)}')
+	}
 
 	smp.initialise()
 
diff --git a/kernel/modules/acpi/acpi.v b/kernel/modules/acpi/acpi.v
index d27703336..a77832066 100644
--- a/kernel/modules/acpi/acpi.v
+++ b/kernel/modules/acpi/acpi.v
@@ -85,18 +85,6 @@ pub fn initialise() {
 	}
 
 	madt_init()
-
-	mut uacpi_status := UACPIStatus.ok
-
-	uacpi_status = C.uacpi_initialize(0)
-	if uacpi_status != UACPIStatus.ok {
-		panic('uacpi_initialize(): ${C.uacpi_status_to_string(uacpi_status)}')
-	}
-
-	uacpi_status = C.uacpi_namespace_load()
-	if uacpi_status != UACPIStatus.ok {
-		panic('uacpi_namespace_load(): ${C.uacpi_status_to_string(uacpi_status)}')
-	}
 }
 
 pub fn find_sdt(signature string, index int) !voidptr {
diff --git a/kernel/modules/acpi/uacpi.v b/kernel/modules/uacpi/uacpi.v
similarity index 97%
rename from kernel/modules/acpi/uacpi.v
rename to kernel/modules/uacpi/uacpi.v
index 24fdd3728..1e67d6258 100644
--- a/kernel/modules/acpi/uacpi.v
+++ b/kernel/modules/uacpi/uacpi.v
@@ -1,4 +1,4 @@
-module acpi
+module uacpi
 
 import klock
 import event
@@ -9,12 +9,9 @@ import memory
 import lib
 import kprint
 import lib.stubs
+import x86.hpet
 
-//#include <uacpi/uacpi.h>
-//#include <uacpi/kernel_api.h>
-
-@[typedef]
-enum UACPIStatus {
+pub enum UACPIStatus {
 	ok = 0
 	mapping_failed = 1
 	out_of_memory = 2
@@ -248,8 +245,7 @@ pub fn uacpi_kernel_unmap(addr voidptr, len u64) {
 
 @[export: 'uacpi_kernel_get_nanoseconds_since_boot']
 pub fn uacpi_kernel_get_nanoseconds_since_boot() u64 {
-	clock := monotonic_clock
-	return u64(clock.tv_sec * 1000000000 + clock.tv_nsec)
+	return hpet.read_counter() * (1000000000 / hpet_frequency)
 }
 
 @[export: 'uacpi_kernel_io_map']
diff --git a/kernel/modules/x86/hpet/hpet.v b/kernel/modules/x86/hpet/hpet.v
new file mode 100644
index 000000000..e0703ac8b
--- /dev/null
+++ b/kernel/modules/x86/hpet/hpet.v
@@ -0,0 +1,66 @@
+module hpet
+
+import acpi
+import x86.kio
+
+@[packed]
+pub struct HPETTable {
+pub mut:
+	header acpi.SDT
+
+	hardware_rev_id u8
+	misc_bits u8
+	pci_vendor_id u16
+	address_space_id u8
+	register_bit_width u8
+	register_bit_offset u8
+	reserved1 u8
+	address u64
+	hpet_number u8
+	minimum_tick u16
+	page_protection u8
+}
+
+pub struct HPET {
+pub mut:
+	general_capabilities u64
+	unused0 u64
+	general_configuration u64
+	unused1 u64
+	general_int_status u64
+	unused2 u64
+	unused3 [24]u64
+	main_counter_value u64
+	unused4 u64
+}
+
+__global (
+	hpet &HPET
+	hpet_frequency u64
+)
+
+pub fn read_counter() u64 {
+	return kio.mmin(&hpet.main_counter_value)
+}
+
+pub fn initialise() {
+	hpet_table := unsafe { &HPETTable(acpi.find_sdt('HPET', 0) or {
+		panic('HPET ACPI table not found')
+	}) }
+
+	hpet = &HPET(hpet_table.address + higher_half)
+
+	mut tmp := kio.mmin(&hpet.general_capabilities)
+
+	counter_clk_period := tmp >> 32;
+	hpet_frequency = u64(1000000000000000) / counter_clk_period
+
+	println('hpet: Detected frequency of ${hpet_frequency} Hz')
+
+	kio.mmout(&hpet.main_counter_value, 0)
+
+	println('hpet: Enabling')
+	tmp = kio.mmin(&hpet.general_configuration)
+	tmp |= 0b01
+	kio.mmout(&hpet.general_configuration, tmp)
+}