feat: enhance timer

kernel/include/apic/timer.h

@@ -1,15 +1,57 @@
 #pragma once
 
 #include "acpi/madt.h"
-#include "util/optional.h"
 
 namespace apic {
 
-struct lapic_timer_calibration_t {
-    uint64_t tsc_frequency_hz;
+struct duration_t {
+    uint64_t timer_count;
 };
 
-optional<lapic_timer_calibration_t> calibrateTimer(const acpi::Madt& madt);
+struct timestamp_t {
+    uint64_t timer_count;
+};
+
+constexpr duration_t operator+(duration_t left, duration_t right) {
+    return duration_t{left.timer_count + right.timer_count};
+}
+
+constexpr duration_t operator-(duration_t left, duration_t right) {
+    return duration_t{left.timer_count - right.timer_count};
+}
+
+constexpr duration_t operator*(duration_t duration, uint64_t scalar) {
+    return duration_t{duration.timer_count * scalar};
+}
+
+constexpr duration_t operator*(uint64_t scalar, duration_t duration) {
+    return duration_t{duration.timer_count * scalar};
+}
+
+constexpr timestamp_t operator+(timestamp_t timestamp, duration_t duration) {
+    return timestamp_t{timestamp.timer_count + duration.timer_count};
+}
+
+constexpr timestamp_t operator+(duration_t duration, timestamp_t timestamp) {
+    return timestamp_t{timestamp.timer_count + duration.timer_count};
+}
+
+constexpr timestamp_t operator-(timestamp_t timestamp, duration_t duration) {
+    return timestamp_t{timestamp.timer_count - duration.timer_count};
+}
+
+constexpr duration_t operator-(timestamp_t left, timestamp_t right) {
+    return duration_t{left.timer_count - right.timer_count};
+}
+
+bool calibrateTimer(const acpi::Madt& madt);
+
+duration_t seconds(uint64_t count);
+duration_t milliseconds(uint64_t count);
+duration_t microseconds(uint64_t count);
+duration_t nanoseconds(uint64_t count);
+
+timestamp_t now();
 
 // TODO: when dynamic allocation and lists are available
 // struct Timer {};

kernel/include/util/function.h

@@ -23,3 +23,10 @@ auto construct() {
         return Type{forward<decltype(args)>(args)...};
     };
 }
+
+template<typename V>
+auto constant(V v) {
+    return [v](auto _) {
+        return v;
+    };
+}

kernel/include/util/optional.h

@@ -183,3 +183,24 @@ public:
         }
     }
 };
+
+template<typename T>
+struct as_optional {
+    using type = optional<T>;
+};
+template<typename T>
+struct as_optional<optional<T>> {
+    using type = optional<T>;
+};
+template<typename T>
+using as_optional_t = typename as_optional<T>::type;
+
+template<typename Func>
+auto lift(Func func) {
+    return [func](const auto&... optionals) -> as_optional_t<decltype(func(optionals.value()...))> {
+        if ((optionals.has_value() && ...)) {
+            return func(optionals.value()...);
+        }
+        return nullopt;
+    };
+}

kernel/src/apic/timer.cpp

@@ -1,7 +1,6 @@
 #include "apic/timer.h"
 
 #include "util/cpuid.h"
-#include "util/function.h"
 
 namespace {
 
@@ -11,6 +10,12 @@ constexpr uint32_t processor_frequency_leaf = 0x16;
 
 constexpr uint32_t feature_edx_tsc = 1u << 4;
 
+struct lapic_timer_calibration_t {
+    uint64_t tsc_frequency_hz;
+};
+
+lapic_timer_calibration_t timer_calibration{};
+
 bool isTscSupported() {
     return cpuid(feature_info_leaf)
         .map([](const cpuid_result_t& features) {
@@ -45,11 +50,46 @@ optional<uint64_t> tscFrequency() {
     return tscFrequencyFromCrystalRatio().or_else(tscFrequencyFromProcessorBase);
 }
 
+apic::duration_t durationFromUnit(uint64_t count, uint64_t units_per_second) {
+    uint64_t whole_seconds = count / units_per_second;
+    uint64_t remainder_units = count % units_per_second;
+    return apic::duration_t{whole_seconds * timer_calibration.tsc_frequency_hz +
+                            remainder_units * timer_calibration.tsc_frequency_hz / units_per_second};
+}
+
 } // namespace
 
-optional<apic::lapic_timer_calibration_t> apic::calibrateTimer(const acpi::Madt&) {
+bool apic::calibrateTimer(const acpi::Madt&) {
     if (!isTscSupported()) {
-        return {};
+        return false;
     }
-    return tscFrequency().map(construct<lapic_timer_calibration_t>());
+    return tscFrequency()
+        .map([](uint64_t tsc_frequency_hz) {
+            timer_calibration.tsc_frequency_hz = tsc_frequency_hz;
+            return true;
+        })
+        .value_or(false);
+}
+
+apic::duration_t apic::seconds(uint64_t count) {
+    return duration_t{count * timer_calibration.tsc_frequency_hz};
+}
+
+apic::duration_t apic::milliseconds(uint64_t count) {
+    return durationFromUnit(count, 1'000);
+}
+
+apic::duration_t apic::microseconds(uint64_t count) {
+    return durationFromUnit(count, 1'000'000);
+}
+
+apic::duration_t apic::nanoseconds(uint64_t count) {
+    return durationFromUnit(count, 1'000'000'000);
+}
+
+apic::timestamp_t apic::now() {
+    uint32_t low = 0;
+    uint32_t high = 0;
+    __asm__ volatile("rdtsc" : "=a"(low), "=d"(high));
+    return timestamp_t{(static_cast<uint64_t>(high) << 32) | low};
 }

kernel/src/init/init.cpp

@@ -1,6 +1,7 @@
 #include "init/init.h"
 #include "acpi/acpi.h"
 #include "acpi/madt.h"
+#include "apic/timer.h"
 #include "init/multiboot2.h"
 #include "init/print.h"
 #include "memory/allocator.h"
@@ -200,10 +201,24 @@ static AcpiDiscoveryResult setupAcpi() {
     return res;
 }
 
+static void calibrateTimer(optional<acpi::Madt> madt) {
+    auto success = madt.map(apic::calibrateTimer).value_or(false);
+    if (!success) {
+        panic("Could not calibrate timer");
+    }
+}
+
 [[maybe_unused]] [[noreturn]] __attribute__((used)) void init() {
     initFromLow();
     print("Reached init\n");
     step("memory", setupMemory);
     auto acpi = step("acpi", setupAcpi);
+    step("timer", partial(calibrateTimer, acpi.madt));
+    auto now = apic::now();
+    print_hex(now.timer_count);
+    now = apic::now();
+    print_hex(now.timer_count);
+    now = apic::now();
+    print_hex(now.timer_count);
     halt();
 }