From 65ef516fd89e6f55872f927a3b8de8118a8ab7a7 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Wed, 2 Oct 2024 19:42:33 -0300
Subject: [PATCH] tsc: redo calibration, directly use hpet

---
 kernel-src/arch/x86-64/hpet.c         | 23 +++++++++++++++++++++++
 kernel-src/arch/x86-64/tsc.c          | 25 +++++++++++++------------
 kernel-src/include/x86-64/arch/hpet.h |  6 +-----
 3 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/kernel-src/arch/x86-64/hpet.c b/kernel-src/arch/x86-64/hpet.c
index 7ceb7929..876950f2 100644
--- a/kernel-src/arch/x86-64/hpet.c
+++ b/kernel-src/arch/x86-64/hpet.c
@@ -4,6 +4,7 @@
 #include <arch/hpet.h>
 #include <kernel/vmm.h>
 #include <kernel/interrupt.h>
+#include <arch/tsc.h>
 
 #include <uacpi/acpi.h>
 #include <uacpi/tables.h>
@@ -165,6 +166,28 @@ time_t hpet_ticks(timekeeper_source_info_t *) {
 	}
 }
 
+time_t arch_hpet_calibrate_tsc(time_t ms_wait) {
+	if (hpet_private.hpet == NULL)
+		return 0;
+
+	long old_ipl = interrupt_raiseipl(IPL_TIMER - 1);
+
+	uint64_t capabilities = read64(HPET_REG_CAPS);
+
+	time_t ticks_to_wait = ms_wait * 1000000000000lu / HPET_CAP_FSPERTICK(capabilities);
+	time_t tsc_tick_start = rdtsc_serialized();
+	time_t tsc_tick_end;
+
+	time_t ticks_target = hpet_ticks(&timekeeper_source_info) + ticks_to_wait;
+
+	do {
+		tsc_tick_end = rdtsc_serialized();
+	} while (hpet_ticks(&timekeeper_source_info) < ticks_target);
+
+	interrupt_loweripl(old_ipl);
+	return (tsc_tick_end - tsc_tick_start) / ms_wait;
+}
+
 TIMEKEEPER_SOURCE(
 	hpet_source,
 	.name = "HPET",
diff --git a/kernel-src/arch/x86-64/tsc.c b/kernel-src/arch/x86-64/tsc.c
index 92955429..18c0c165 100644
--- a/kernel-src/arch/x86-64/tsc.c
+++ b/kernel-src/arch/x86-64/tsc.c
@@ -15,7 +15,11 @@ static bool tsc_probe(void) {
 	return cpuid_results.edx & (1 << 8);
 }
 
+static MUTEX_DEFINE(init_mutex);
+static time_t ticks_per_us;
+
 static timekeeper_source_info_t *tsc_init(void) {
+	MUTEX_ACQUIRE(&init_mutex, false);
 	__assert(tsc_probe());
 
 	timekeeper_source_info_t *timekeeper_source_info = alloc(sizeof(timekeeper_source_info_t));
@@ -23,6 +27,9 @@ static timekeeper_source_info_t *tsc_init(void) {
 
 	timekeeper_source_info->private = current_cpu();
 
+	if (ticks_per_us)
+		goto leave;
+
 	bool need_calibration = false;
 	if (cpuid_base_max_leaf() >= 0x15) {
 		cpuid_results_t cpuid_results;
@@ -38,24 +45,18 @@ static timekeeper_source_info_t *tsc_init(void) {
 		uint64_t core_denominator = cpuid_results.eax;
 
 		uint64_t tsc_frequency = core_frequency * core_numerator / core_denominator;
-		timekeeper_source_info->ticks_per_us = tsc_frequency / 1000000;
+		ticks_per_us = tsc_frequency / 1000000;
 	}
 
 	calibrate:
 	if (need_calibration) {
-		for (int i = 0; i < 10; ++i) {
-			long old_ipl = interrupt_raiseipl(IPL_TIMER - 1);
-			time_t ticks_start = rdtsc_serialized();
-
-			timekeeper_wait_us(50000);
-			time_t ticks_end = rdtsc_serialized();
-
-			interrupt_loweripl(old_ipl);
-
-			timekeeper_source_info->ticks_per_us = (ticks_end - ticks_start) / 50000;
-		}
+		ticks_per_us = arch_hpet_calibrate_tsc(200) / 1000;
+		__assert(ticks_per_us);
 	}
 
+	leave:
+	timekeeper_source_info->ticks_per_us = ticks_per_us;
+	MUTEX_RELEASE(&init_mutex);
 	return timekeeper_source_info;
 }
 
diff --git a/kernel-src/include/x86-64/arch/hpet.h b/kernel-src/include/x86-64/arch/hpet.h
index 33784bbd..0d277c9d 100644
--- a/kernel-src/include/x86-64/arch/hpet.h
+++ b/kernel-src/include/x86-64/arch/hpet.h
@@ -4,10 +4,6 @@
 #include <stdbool.h>
 #include <time.h>
 
-time_t arch_hpet_ticks();
-void arch_hpet_waitticks(time_t ticks);
-void arch_hpet_waitus(time_t us);
-bool arch_hpet_exists();
-time_t arch_hpet_init();
+time_t arch_hpet_calibrate_tsc(time_t ms_wait);
 
 #endif