From 6c468a134b0c0f806a6f9b012aeaf4d8b662368b Mon Sep 17 00:00:00 2001
From: "Justin C. Miller" <justin@devjustinian.com>
Date: Sun, 28 Jun 2020 17:47:46 -0700
Subject: [PATCH] [kernel] Add HPET support, create clock class

Create a clock class which can be queried for current timestamp in
nanoseconds. Also implements a simple HPET class as one possible clock
source.

Tags: time
---
 modules.yaml                  |   2 +
 src/include/log_areas.inc     |   2 +
 src/kernel/acpi_tables.h      |  10 +++
 src/kernel/apic.cpp           |  43 ++++--------
 src/kernel/apic.h             |   4 +-
 src/kernel/clock.cpp          |  22 +++++++
 src/kernel/clock.h            |  44 +++++++++++++
 src/kernel/device_manager.cpp |  50 ++++++++++++++
 src/kernel/device_manager.h   |  34 +++++++++-
 src/kernel/hpet.cpp           | 120 ++++++++++++++++++++++++++++++++++
 src/kernel/hpet.h             |  50 ++++++++++++++
 src/kernel/main.cpp           |   1 +
 src/kernel/scheduler.cpp      |   1 +
 13 files changed, 347 insertions(+), 36 deletions(-)
 create mode 100644 src/kernel/clock.cpp
 create mode 100644 src/kernel/clock.h
 create mode 100644 src/kernel/hpet.cpp
 create mode 100644 src/kernel/hpet.h

diff --git a/modules.yaml b/modules.yaml
index f41ee86..ebdd98f 100644
--- a/modules.yaml
+++ b/modules.yaml
@@ -16,6 +16,7 @@ modules:
             - src/kernel/apic.cpp
             - src/kernel/assert.cpp
             - src/kernel/boot.s
+            - src/kernel/clock.cpp
             - src/kernel/console.cpp
             - src/kernel/cpprt.cpp
             - src/kernel/cpu.cpp
@@ -27,6 +28,7 @@ modules:
             - src/kernel/fs/gpt.cpp
             - src/kernel/gdt.cpp
             - src/kernel/gdt.s
+            - src/kernel/hpet.cpp
             - src/kernel/interrupts.cpp
             - src/kernel/interrupts.s
             - src/kernel/io.cpp
diff --git a/src/include/log_areas.inc b/src/include/log_areas.inc
index 8c49c4b..cdfa47b 100644
--- a/src/include/log_areas.inc
+++ b/src/include/log_areas.inc
@@ -10,3 +10,5 @@ LOG(boot,   debug);
 LOG(syscall,debug);
 LOG(vmem,   debug);
 LOG(objs,   debug);
+LOG(timer,  debug);
+LOG(clock,  debug);
diff --git a/src/kernel/acpi_tables.h b/src/kernel/acpi_tables.h
index 551f4f4..c990968 100644
--- a/src/kernel/acpi_tables.h
+++ b/src/kernel/acpi_tables.h
@@ -188,3 +188,13 @@ struct acpi_mcfg
 	acpi_mcfg_entry entries[0];
 } __attribute__ ((packed));
 
+struct acpi_hpet
+{
+	TABLE_HEADER('HPET');
+	uint32_t hardware_id;
+	acpi_gas base_address;
+	uint8_t index;
+	uint16_t periodic_min;
+	uint8_t attributes;
+} __attribute__ ((packed));
+
diff --git a/src/kernel/apic.cpp b/src/kernel/apic.cpp
index 276cb86..a39ee0a 100644
--- a/src/kernel/apic.cpp
+++ b/src/kernel/apic.cpp
@@ -1,5 +1,6 @@
 #include "kutil/assert.h"
 #include "apic.h"
+#include "clock.h"
 #include "interrupts.h"
 #include "io.h"
 #include "log.h"
@@ -67,36 +68,20 @@ lapic::calibrate_timer()
 
 	log::info(logs::apic, "Calibrating APIC timer...");
 
-	// Set up PIT sleep
-	uint8_t command = 0x30; // channel 0, loybyte/highbyte, mode 0
-	outb(0x43, command);
-
 	const uint32_t initial = -1u;
 	enable_timer(isr::isrSpurious);
 	set_divisor(1);
 	apic_write(m_base, lapic_timer_init, initial);
 
-	const int iterations = 5;
-	for (int i=0; i<iterations; ++i) {
-		const uint16_t pit_33ms = 39375;
-		uint16_t pit_count = pit_33ms;
-		outb(0x40, pit_count & 0xff);
-		io_wait();
-		outb(0x40, (pit_count >> 8) & 0xff);
-
-
-		while (pit_count <= pit_33ms) {
-			outb(0x43, 0); // latch counter values
-			pit_count =
-				static_cast<uint16_t>(inb(0x40)) |
-				static_cast<uint16_t>(inb(0x40)) << 8;
-		}
-	}
+	uint64_t us = 200000;
+	uint64_t ns = us * 1000;
+	clock::get().spinwait(ns);
 
 	uint32_t remaining = apic_read(m_base, lapic_timer_cur);
 	uint32_t ticks_total = initial - remaining;
-	m_ticks_per_us = ticks_total / (iterations * 33000);
-	log::info(logs::apic, "APIC timer ticks %d times per nanosecond.", m_ticks_per_us);
+	m_ticks_per_us = ticks_total / us;
+
+	log::info(logs::apic, "APIC timer ticks %d times per microsecond.", m_ticks_per_us);
 
 	interrupts_enable();
 }
@@ -123,14 +108,6 @@ lapic::set_divisor(uint8_t divisor)
 	m_divisor = divisor;
 }
 
-uint32_t
-lapic::enable_timer_internal(isr vector, uint8_t divisor, uint32_t count, bool repeat)
-{
-
-	reset_timer(count);
-	return count;
-}
-
 void
 lapic::enable_timer(isr vector, bool repeat)
 {
@@ -224,6 +201,9 @@ ioapic::ioapic(uint32_t *base, uint32_t base_gsi) :
 void
 ioapic::redirect(uint8_t irq, isr vector, uint16_t flags, bool masked)
 {
+	log::debug(logs::apic, "IOAPIC %d redirecting irq %3d to vector %3d [%04x]%s",
+			m_id, irq, vector, flags, masked ? " (masked)" : "");
+
 	uint64_t entry = static_cast<uint64_t>(vector);
 
 	uint16_t polarity = flags & 0x3;
@@ -244,6 +224,9 @@ ioapic::redirect(uint8_t irq, isr vector, uint16_t flags, bool masked)
 void
 ioapic::mask(uint8_t irq, bool masked)
 {
+	log::debug(logs::apic, "IOAPIC %d %smasking irq %3d",
+			m_id, masked ? "" : "un", irq);
+
 	uint32_t entry = ioapic_read(m_base, (2 * irq) + 0x10);
 	if (masked)
 		entry |= (1 << 16);
diff --git a/src/kernel/apic.h b/src/kernel/apic.h
index 26db853..3650d30 100644
--- a/src/kernel/apic.h
+++ b/src/kernel/apic.h
@@ -6,7 +6,6 @@
 
 enum class isr : uint8_t;
 
-
 /// Base class for other APIC types
 class apic
 {
@@ -54,7 +53,7 @@ public:
 	void enable();  ///< Enable servicing of interrupts
 	void disable(); ///< Disable (temporarily) servicing of interrupts
 
-	/// Calibrate the timer speed against the PIT
+	/// Calibrate the timer speed against the clock
 	void calibrate_timer();
 
 private:
@@ -68,7 +67,6 @@ private:
 
 	void set_divisor(uint8_t divisor);
 	void set_repeat(bool repeat);
-	uint32_t enable_timer_internal(isr vector, uint8_t divisor, uint32_t count, bool repeat);
 
 	uint32_t m_divisor;
 	uint32_t m_ticks_per_us;
diff --git a/src/kernel/clock.cpp b/src/kernel/clock.cpp
new file mode 100644
index 0000000..b51b1c1
--- /dev/null
+++ b/src/kernel/clock.cpp
@@ -0,0 +1,22 @@
+#include "clock.h"
+
+clock * clock::s_instance = nullptr;
+
+clock::clock(uint64_t rate, clock::source source_func, void *data) :
+	m_rate(rate),
+	m_data(data),
+	m_source(source_func)
+{
+	// TODO: make this atomic
+	if (s_instance == nullptr)
+		s_instance = this;
+	update();
+}
+
+void
+clock::spinwait(uint64_t ns) const
+{
+	uint64_t when = m_source(m_data) + ns;
+	while (value() < when);
+}
+
diff --git a/src/kernel/clock.h b/src/kernel/clock.h
new file mode 100644
index 0000000..4b73843
--- /dev/null
+++ b/src/kernel/clock.h
@@ -0,0 +1,44 @@
+#pragma once
+/// \file clock.h
+/// The kernel time keeping interface
+
+#include <stdint.h>
+
+class clock
+{
+public:
+	/// A source is a function that returns the current
+	/// value of some clock source.
+	using source = uint64_t (*)(void*);
+
+	/// Constructor.
+	/// \arg rate   Number of source ticks per ns
+	/// \arg source Function for the clock source
+	/// \arg data   Data to pass to the source function
+	clock(uint64_t rate, source source_func, void *data);
+
+	/// Get the current value of the clock.
+	/// \returns Current value of the source, in ns
+	/// TODO: optimize divison by finding a multiply and
+	/// shift value instead
+	inline uint64_t value() const { return m_source(m_data) / m_rate; }
+
+	/// Update the internal state via the source
+	/// \returns Current value of the clock
+	inline void update() { m_current = value(); return m_current; }
+
+	/// Wait in a tight loop
+	/// \arg interval  Time to wait, in ns
+	void spinwait(uint64_t ns) const;
+
+	/// Get the master clock
+	static clock & get() { return *s_instance; }
+
+private:
+	uint64_t m_current; ///< current ns count
+	uint64_t m_rate; ///< source ticks per ns
+	void *m_data;
+	source m_source;
+
+	static clock *s_instance;
+};
diff --git a/src/kernel/device_manager.cpp b/src/kernel/device_manager.cpp
index beee7b8..6d979de 100644
--- a/src/kernel/device_manager.cpp
+++ b/src/kernel/device_manager.cpp
@@ -5,6 +5,7 @@
 #include "kutil/memory.h"
 #include "acpi_tables.h"
 #include "apic.h"
+#include "clock.h"
 #include "console.h"
 #include "device_manager.h"
 #include "interrupts.h"
@@ -135,6 +136,10 @@ device_manager::load_xsdt(const acpi_xsdt *xsdt)
 			load_mcfg(reinterpret_cast<const acpi_mcfg *>(header));
 			break;
 
+		case acpi_hpet::type_id:
+			load_hpet(reinterpret_cast<const acpi_hpet *>(header));
+			break;
+
 		default:
 			break;
 		}
@@ -268,6 +273,27 @@ device_manager::load_mcfg(const acpi_mcfg *mcfg)
 	probe_pci();
 }
 
+void
+device_manager::load_hpet(const acpi_hpet *hpet)
+{
+	log::debug(logs::device, "  Found HPET device #%3d: base %016lx  pmin %d  attr %02x",
+			hpet->index, hpet->base_address.address, hpet->periodic_min, hpet->attributes);
+
+	uint32_t hwid = hpet->hardware_id;
+	uint8_t rev_id = hwid & 0xff;
+	uint8_t comparators = (hwid >> 8) & 0x1f;
+	uint8_t count_size_cap = (hwid >> 13) & 1;
+	uint8_t legacy_replacement = (hwid >> 15) & 1;
+	uint32_t pci_vendor_id = (hwid >> 16);
+
+	log::debug(logs::device, "      rev:%02d comparators:%02d count_size_cap:%1d legacy_repl:%1d",
+			rev_id, comparators, count_size_cap, legacy_replacement);
+	log::debug(logs::device, "      pci vendor id: %04x", pci_vendor_id);
+
+	m_hpets.emplace(hpet->index,
+		reinterpret_cast<uint64_t*>(hpet->base_address.address + ::memory::page_offset));
+}
+
 void
 device_manager::probe_pci()
 {
@@ -308,6 +334,30 @@ device_manager::init_drivers()
 		ahcid.register_device(&device);
 	}
 	*/
+	if (m_hpets.count() > 0) {
+		hpet &h = m_hpets[0];
+		h.enable();
+
+		// becomes the singleton
+		clock *master_clock = new clock(h.rate(), hpet_clock_source, &h);
+		kassert(master_clock, "Failed to allocate master clock");
+		log::info(logs::clock, "Created master clock using HPET 0: Rate %d", h.rate());
+	} else {
+		//TODO: APIC clock?
+	}
+}
+
+bool
+device_manager::install_irq(unsigned irq, const char *name, irq_callback cb, void *data)
+{
+	if (irq >= m_irqs.count())
+		m_irqs.set_size(irq+1);
+
+	if (m_irqs[irq].callback != nullptr)
+		return false;
+
+	m_irqs[irq] = {name, cb, data};
+	return true;
 }
 
 bool
diff --git a/src/kernel/device_manager.h b/src/kernel/device_manager.h
index 6701b17..5464a3a 100644
--- a/src/kernel/device_manager.h
+++ b/src/kernel/device_manager.h
@@ -3,11 +3,13 @@
 /// The device manager definition
 #include "kutil/vector.h"
 #include "apic.h"
+#include "hpet.h"
 #include "pci.h"
 
 struct acpi_xsdt;
 struct acpi_apic;
 struct acpi_mcfg;
+struct acpi_hpet;
 class block_device;
 
 using irq_callback = void (*)(void *);
@@ -41,6 +43,18 @@ public:
 	/// Intialize drivers for the current device list.
 	void init_drivers();
 
+	/// Install an IRQ callback for a device
+	/// \arg irq   IRQ to install the handler for
+	/// \arg name  Name of the interrupt, for display to user
+	/// \arg cb    Callback to call when the interrupt is received
+	/// \arg data  Data to pass to the callback
+	/// \returns   True if an IRQ was installed successfully
+	bool install_irq(
+			unsigned irq,
+			const char *name,
+			irq_callback cb,
+			void *data);
+
 	/// Allocate an MSI IRQ for a device
 	/// \arg name    Name of the interrupt, for display to user
 	/// \arg device  Device this MSI is being allocated for
@@ -85,6 +99,15 @@ public:
 			m_blockdevs[i] : nullptr;
 	}
 
+	/// Get an HPET device
+	/// \arg i    Index of the device to get
+	/// \returns  A pointer to the requested device, or nullptr
+	inline hpet * get_hpet(unsigned i)
+	{
+		return i < m_hpets.count() ?
+			&m_hpets[i] : nullptr;
+	}
+
 private:
 	/// Parse the ACPI XSDT and load relevant sub-tables.
 	/// \arg xsdt  Pointer to the XSDT from the firmware
@@ -98,6 +121,10 @@ private:
 	/// \arg mcfg  Pointer to the MCFG from the XSDT
 	void load_mcfg(const acpi_mcfg *mcfg);
 
+	/// Parse the ACPI HPET and initialize an HPET from it.
+	/// \arg hpet  Pointer to the HPET from the XSDT
+	void load_hpet(const acpi_hpet *hpet);
+
 	/// Probe the PCIe busses and add found devices to our
 	/// device list. The device list is destroyed and rebuilt.
 	void probe_pci();
@@ -108,15 +135,16 @@ private:
 
 	lapic *m_lapic;
 	kutil::vector<ioapic> m_ioapics;
+	kutil::vector<hpet> m_hpets;
 
 	kutil::vector<pci_group> m_pci;
 	kutil::vector<pci_device> m_devices;
 
 	struct irq_allocation
 	{
-		const char *name;
-		irq_callback callback;
-		void *data;
+		const char *name = nullptr;
+		irq_callback callback = nullptr;
+		void *data = nullptr;
 	};
 	kutil::vector<irq_allocation> m_irqs;
 
diff --git a/src/kernel/hpet.cpp b/src/kernel/hpet.cpp
new file mode 100644
index 0000000..3d75bb2
--- /dev/null
+++ b/src/kernel/hpet.cpp
@@ -0,0 +1,120 @@
+#include "kernel_memory.h"
+#include "kutil/assert.h"
+#include "device_manager.h"
+#include "hpet.h"
+#include "io.h"
+#include "log.h"
+
+namespace {
+	inline uint64_t volatile *capabilities(uint64_t volatile *base) { return base; }
+	inline uint64_t volatile *configuration(uint64_t volatile *base) { return base+2; }
+	inline uint64_t volatile *interrupt_status(uint64_t volatile *base) { return base+4; }
+	inline uint64_t volatile *counter_value(uint64_t volatile *base) { return base+30; }
+
+	inline uint64_t volatile *timer_base(uint64_t volatile *base, unsigned i) { return base + 0x20 + (4*i); }
+	inline uint64_t volatile *timer_config(uint64_t volatile *base, unsigned i) { return timer_base(base, i); }
+	inline uint64_t volatile *timer_comparator(uint64_t volatile *base, unsigned i) { return timer_base(base, i) + 1; }
+}
+
+
+void
+hpet_irq_callback(void *hpet_ptr)
+{
+	if (hpet_ptr)
+		reinterpret_cast<hpet*>(hpet_ptr)->callback();
+}
+
+
+hpet::hpet(uint8_t index, uint64_t *base) :
+	m_index(index),
+	m_base(base)
+{
+	*configuration(m_base) = 0;
+	*counter_value(m_base) = 0;
+
+	uint64_t caps = *capabilities(base);
+	uint64_t config = *configuration(base);
+	m_timers = ((caps >> 8) & 0x1f) + 1;
+	m_period = (caps >> 32);
+
+	// setup_timer_interrupts(0, 2, 1000000, true);
+	// bool installed = device_manager::get()
+	// 	.install_irq(2, "HPET Timer", hpet_irq_callback, this);
+	// kassert(installed, "Installing HPET IRQ handler");
+
+	log::debug(logs::timer, "HPET %d capabilities:", index);
+	log::debug(logs::timer, "       revision: %d", caps & 0xff);
+	log::debug(logs::timer, "         timers: %d", m_timers);
+	log::debug(logs::timer, "           bits: %d", ((caps >> 13) & 1) ? 64 : 32);
+	log::debug(logs::timer, "    LRR capable: %d", ((caps >> 15) & 1));
+	log::debug(logs::timer, "         period: %dns", m_period / 1000000);
+	log::debug(logs::timer, " global enabled: %d", config & 1);
+	log::debug(logs::timer, "     LRR enable: %d", (config >> 1) & 1);
+
+	for (unsigned i = 0; i < m_timers; ++i) {
+		disable_timer(i);
+		uint64_t config = *timer_config(m_base, i);
+
+		log::debug(logs::timer, "HPET %d timer %d:", index, i);
+		log::debug(logs::timer, "       int type: %d", (config >> 1) & 1);
+		log::debug(logs::timer, "     timer type: %d", (config >> 3) & 1);
+		log::debug(logs::timer, "   periodic cap: %d", (config >> 4) & 1);
+		log::debug(logs::timer, "           bits: %d", ((config >> 5) & 1) ? 64 : 32);
+		log::debug(logs::timer, "        32 mode: %d", (config >> 8) & 1);
+		log::debug(logs::timer, "      int route: %d", (config >> 9) & 0x1f);
+		log::debug(logs::timer, "     FSB enable: %d", (config >> 14) & 1);
+		log::debug(logs::timer, "    FSB capable: %d", (config >> 15) & 1);
+		log::debug(logs::timer, "     rotung cap: %08x", (config >> 32));
+	}
+
+}
+
+void
+hpet::setup_timer_interrupts(unsigned timer, uint8_t irq, uint64_t interval, bool periodic)
+{
+	constexpr uint64_t femto_per_ns = 1000000ull;
+	*timer_comparator(m_base, timer) =
+		*counter_value(m_base) +
+		(interval * femto_per_ns) / m_period;
+
+	*timer_config(m_base, timer) = (irq << 9) | ((periodic ? 1 : 0) << 3);
+}
+
+void
+hpet::enable_timer(unsigned timer)
+{
+	*timer_config(m_base, timer) = *timer_config(m_base, timer) | (1 << 2);
+}
+
+void
+hpet::disable_timer(unsigned timer)
+{
+	*timer_config(m_base, timer) = *timer_config(m_base, timer) & ~(1ull << 2);
+}
+
+void
+hpet::callback()
+{
+	log::debug(logs::timer, "HPET %d got irq", m_index);
+}
+
+void
+hpet::enable()
+{
+	log::debug(logs::timer, "HPET %d enabling", m_index);
+
+	enable_timer(0);
+	*configuration(m_base) = 1;
+}
+
+uint64_t
+hpet::value() const
+{
+	return *counter_value(m_base);
+}
+
+uint64_t
+hpet_clock_source(void *data)
+{
+	return reinterpret_cast<hpet*>(data)->value();
+}
diff --git a/src/kernel/hpet.h b/src/kernel/hpet.h
new file mode 100644
index 0000000..025137a
--- /dev/null
+++ b/src/kernel/hpet.h
@@ -0,0 +1,50 @@
+#pragma once
+/// \file hpet.h
+/// Definitions for handling the HPET timer
+
+#include <stdint.h>
+
+/// Source function for the clock that takes a pointer to
+/// an hpet object.
+uint64_t hpet_clock_source(void *);
+
+/// Represents a single HPET timer
+class hpet
+{
+public:
+	/// Constructor.
+	/// \arg index  The index of the HPET out of all HPETs
+	/// \arg base   The base address of the HPET for MMIO
+	hpet(uint8_t index, uint64_t *base);
+
+	/// Configure the timer and start it running.
+	void enable();
+
+	/// Wait in a tight loop while reading the HPET counter.
+	/// \arg ns  Number of nanoseconds to wait
+	void spinwait(uint64_t ns) const;
+
+	/// Get the timer rate in ticks per ns
+	inline uint64_t rate() const { return m_period * 1000000ull; }
+
+	/// Get the current timer value
+	uint64_t value() const;
+
+private:
+	friend void hpet_irq_callback(void *);
+	friend uint64_t hpet_clock_source(void *);
+
+	void setup_timer_interrupts(unsigned timer, uint8_t irq, uint64_t interval, bool periodic);
+	void enable_timer(unsigned timer);
+	void disable_timer(unsigned timer);
+
+	void callback();
+
+	uint8_t m_timers;
+	uint8_t m_index;
+
+	uint64_t m_period;
+	volatile uint64_t *m_base;
+};
+
+
diff --git a/src/kernel/main.cpp b/src/kernel/main.cpp
index 21f3a84..e9d8f00 100644
--- a/src/kernel/main.cpp
+++ b/src/kernel/main.cpp
@@ -169,6 +169,7 @@ kernel_main(args::header *header)
 	*/
 
 	devices.get_lapic()->calibrate_timer();
+	devices.init_drivers();
 
 	syscall_enable();
 	scheduler *sched = new (&scheduler::get()) scheduler(devices.get_lapic());
diff --git a/src/kernel/scheduler.cpp b/src/kernel/scheduler.cpp
index 8f5fdf1..ca78340 100644
--- a/src/kernel/scheduler.cpp
+++ b/src/kernel/scheduler.cpp
@@ -311,6 +311,7 @@ scheduler::schedule()
 		m_blocked.push_back(m_current);
 	}
 
+	clock::get().update();
 	prune(++m_clock);
 
 	priority = 0;