Kernel: Introduce the PIT class

The PIT class inherits from HardwareTimer class, and is replacing
the PIT namespace.

Kernel/Devices/PIT.cpp

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <Kernel/Arch/i386/CPU.h>
+#include <Kernel/Devices/PIT.h>
+#include <Kernel/Interrupts/PIC.h>
+#include <Kernel/Scheduler.h>
+#include <Kernel/Thread.h>
+#include <LibBareMetal/IO.h>
+
+#define IRQ_TIMER 0
+namespace Kernel {
+
+//#define PIT_DEBUG
+
+static PIT* s_the;
+
+void PIT::initialize()
+{
+    if (s_the == nullptr) {
+        s_the = new PIT();
+    }
+}
+
+PIT& PIT::the()
+{
+    ASSERT(s_the != nullptr);
+    return *s_the;
+}
+
+inline static void reset_countdown(u16 timer_reload)
+{
+    IO::out8(PIT_CTL, TIMER0_SELECT | WRITE_WORD | MODE_COUNTDOWN);
+    IO::out8(TIMER0_CTL, LSB(timer_reload));
+    IO::out8(TIMER0_CTL, MSB(timer_reload));
+}
+
+void PIT::handle_irq(RegisterState& regs)
+{
+#ifdef PIT_DEBUG
+    dbg() << "PIT: Debugging Interrupt.";
+#endif
+    if (++m_ticks_this_second >= TICKS_PER_SECOND) {
+        // FIXME: Synchronize with the RTC somehow to prevent drifting apart.
+        ++m_seconds_since_boot;
+        m_ticks_this_second = 0;
+    }
+    Scheduler::timer_tick(regs);
+}
+
+u32 PIT::ticks_this_second() const
+{
+    return m_ticks_this_second;
+}
+
+PIT::PIT()
+    : HardwareTimer(IRQ_TIMER)
+    , m_default_timer_reload(BASE_FREQUENCY / TICKS_PER_SECOND)
+    , m_ticks_this_second(0)
+{
+
+    IO::out8(PIT_CTL, TIMER0_SELECT | WRITE_WORD | MODE_SQUARE_WAVE);
+
+    kprintf("PIT: %u Hz, square wave (%x)\n", TICKS_PER_SECOND, m_default_timer_reload);
+
+    IO::out8(TIMER0_CTL, LSB(m_default_timer_reload));
+    IO::out8(TIMER0_CTL, MSB(m_default_timer_reload));
+
+    enable_irq();
+}
+
+}

Kernel/Devices/PIT.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <Kernel/Devices/HardwareTimer.h>
+
+namespace Kernel {
+
+#define TICKS_PER_SECOND 1000
+/* Timer related ports */
+#define TIMER0_CTL 0x40
+#define TIMER1_CTL 0x41
+#define TIMER2_CTL 0x42
+#define PIT_CTL 0x43
+
+/* Building blocks for PIT_CTL */
+#define TIMER0_SELECT 0x00
+#define TIMER1_SELECT 0x40
+#define TIMER2_SELECT 0x80
+
+#define MODE_COUNTDOWN 0x00
+#define MODE_ONESHOT 0x02
+#define MODE_RATE 0x04
+#define MODE_SQUARE_WAVE 0x06
+
+#define WRITE_WORD 0x30
+
+#define BASE_FREQUENCY 1193182
+
+class PIT : public HardwareTimer {
+public:
+    static void initialize();
+    static PIT& the();
+    u32 ticks_this_second() const;
+
+private:
+    PIT();
+    // ^IRQHandler
+    virtual void handle_irq(RegisterState& regs) override;
+
+    u16 m_default_timer_reload;
+    u16 m_variable_timer_reload;
+    u32 m_ticks_this_second;
+};
+}