x86_64: implement legacy PIT driver

2 files changed, 55 insertions, 1 deletions

diff --git a/arch/x86_64/src/cpu/initialization.cpp b/arch/x86_64/src/cpu/initialization.cpp
index 878fa07..b808c76 100644
--- a/arch/x86_64/src/cpu/initialization.cpp
+++ b/arch/x86_64/src/cpu/initialization.cpp
@@ -139,7 +139,7 @@ namespace arch::cpu
     constexpr auto pic_cascade_address = std::uint8_t{0x04};
     constexpr auto pic_cascade_slave_identity = std::uint8_t{0x02};
     constexpr auto pic_use_8086_mode = std::uint8_t{0x01};
-    constexpr auto pic_master_mask = std::uint8_t{0x01};
+    constexpr auto pic_master_mask = std::uint8_t{0x00};
     constexpr auto pic_slave_mask = std::uint8_t{0x00};
 
     pic_master_control_port::write(pic_init_command);
diff --git a/arch/x86_64/src/devices/legacy_pit.cpp b/arch/x86_64/src/devices/legacy_pit.cpp
new file mode 100644
index 0000000..f2fb70e
--- /dev/null
+++ b/arch/x86_64/src/devices/legacy_pit.cpp
@@ -0,0 +1,54 @@
+#include "arch/devices/legacy_pit.hpp"
+
+#include "kapi/devices.hpp"
+#include "kapi/devices/device.hpp"
+#include "kapi/interrupts.hpp"
+
+#include "arch/device_io/port_io.hpp"
+
+#include <cstdint>
+
+namespace arch::devices
+{
+
+  namespace
+  {
+    using command_port = io::port<0x43, std::uint8_t, io::port_write>;
+    using channel_0_port = io::port<0x40, std::uint8_t, io::port_write>;
+    using channel_1_port = io::port<0x41, std::uint8_t, io::port_write>;
+    using channel_2_port = io::port<0x42, std::uint8_t, io::port_write>;
+  }  // namespace
+
+  legacy_pit::legacy_pit(std::uint32_t frequency_in_hz)
+      : kapi::devices::device{kapi::devices::allocate_major_number(), 0, "legacy_pit"}
+      , m_irq_number{0}
+      , m_frequency_in_hz{frequency_in_hz}
+  {}
+
+  auto legacy_pit::init() -> bool
+  {
+    constexpr auto base_frequency = 1'193'182u;
+    auto divisor = static_cast<std::uint16_t>(base_frequency / m_frequency_in_hz);
+
+    kapi::interrupts::register_handler(m_irq_number, *this);
+
+    command_port::write<std::uint8_t>(0x36);                   // NOLINT
+    channel_0_port::write<std::uint8_t>(divisor & 0xff);       // NOLINT
+    channel_0_port::write<std::uint8_t>(divisor >> 8 & 0xff);  // NOLINT
+
+    return true;
+  }
+
+  auto legacy_pit::handle_interrupt(std::uint32_t irq_number) -> kapi::interrupts::status
+  {
+    if (irq_number != m_irq_number)
+    {
+      return kapi::interrupts::status::unhandled;
+    }
+
+    ++m_ticks;
+
+    return kapi::interrupts::status::handled;
+  }
+
+}  // namespace arch::devices
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