x86_64: ensure PIT is not overwhelmed on config

2 files changed, 14 insertions, 4 deletions

diff --git a/arch/x86_64/include/arch/device_io/port_io.hpp b/arch/x86_64/include/arch/device_io/port_io.hpp
index 70773dd..4c8d66a 100644
--- a/arch/x86_64/include/arch/device_io/port_io.hpp
+++ b/arch/x86_64/include/arch/device_io/port_io.hpp
@@ -102,6 +102,11 @@ namespace arch::io
                                                       : std::string_view{"eax"};
   };
 
+  auto inline wait() -> void
+  {
+    port<0x80, std::uint8_t, port_write>::write<std::uint8_t>(0);
+  }
+
 }  // namespace arch::io
 
 #endif
\ No newline at end of file
diff --git a/arch/x86_64/src/devices/legacy_pit.cpp b/arch/x86_64/src/devices/legacy_pit.cpp
index 970f538..a8df3c3 100644
--- a/arch/x86_64/src/devices/legacy_pit.cpp
+++ b/arch/x86_64/src/devices/legacy_pit.cpp
@@ -18,6 +18,9 @@ namespace arch::devices
     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>;
+
+    constexpr auto base_frequency = 1'193'182u;
+    constexpr auto square_wave_mode = 0x36;
   }  // namespace
 
   legacy_pit::legacy_pit(std::size_t major, std::uint32_t frequency_in_hz)
@@ -28,14 +31,16 @@ namespace arch::devices
 
   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
+    command_port::write<std::uint8_t>(square_wave_mode);
+    io::wait();
+    channel_0_port::write<std::uint8_t>(divisor & 0xff);
+    io::wait();
+    channel_0_port::write<std::uint8_t>(divisor >> 8 & 0xff);
+    io::wait();
 
     return true;
   }