From b1cf9e5dfbc8967bd7cb2a22ec1e5e521f4e0e6e Mon Sep 17 00:00:00 2001
From: Benji Dial <benji@benjidial.net>
Date: Wed, 31 Jul 2024 13:36:53 -0400
Subject: add clock

---
 kernel/source/timer.cpp | 117 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 kernel/source/timer.cpp

(limited to 'kernel/source/timer.cpp')

diff --git a/kernel/source/timer.cpp b/kernel/source/timer.cpp
new file mode 100644
index 0000000..d6d37d7
--- /dev/null
+++ b/kernel/source/timer.cpp
@@ -0,0 +1,117 @@
+#include <hilbert/kernel/timer.hpp>
+
+namespace hilbert::kernel::timer {
+
+  struct sleeping_thread {
+    uint64_t sleeping_until;
+    application::thread *thread;
+  };
+
+  //sorted ascending by sleeping_until
+  static utility::list<sleeping_thread> *sleeping_threads;
+
+  uint64_t current_time;
+
+  //output is
+  //   seconds     | (minutes <<  8) | (hours << 16) |
+  //  (days << 24) | ( months << 32) | (years << 40)
+  extern "C" uint64_t get_time_from_rtc();
+
+  //index is (year % 4) * 12 + month - 1;
+  //output is days from january 1st 2000 to [month] 1st [year]
+  static uint16_t month_table[] {
+       0,   31,   60,   91,  121,  152,
+     182,  213,  244,  274,  305,  335,
+     366,  397,  425,  456,  486,  517,
+     547,  578,  609,  639,  670,  700,
+     731,  762,  790,  821,  851,  882,
+     912,  943,  974, 1004, 1035, 1065,
+    1096, 1127, 1155, 1186, 1216, 1247,
+    1277, 1308, 1339, 1369, 1400, 1430
+  };
+
+  //index is (year % 4) * 12 + month - 1;
+  //output is days in that month
+  static uint8_t month_table_2[] = {
+    31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+  };
+
+  void clamp(uint8_t &value, uint8_t min, uint8_t max) {
+    if (value < min)
+      value = min;
+    else if (value > max)
+      value = max;
+  }
+
+  extern "C" void enable_rtc_interrupts();
+
+  void init_timer() {
+
+    sleeping_threads = new utility::list<sleeping_thread>();
+
+    uint64_t rtc_time = get_time_from_rtc();
+
+    uint8_t   years =  rtc_time >> 40;
+    uint8_t  months = (rtc_time >> 32) & 0xff;
+    uint8_t    days = (rtc_time >> 24) & 0xff;
+    uint8_t   hours = (rtc_time >> 16) & 0xff;
+    uint8_t minutes = (rtc_time >>  8) & 0xff;
+    uint8_t seconds =  rtc_time        & 0xff;
+
+    uint8_t month_table_index =
+      (years % 4) * 12 + months - 1;
+
+    clamp(  years, 0, 99);
+    clamp( months, 1, 12);
+    clamp(   days, 1, month_table_2[month_table_index]);
+    clamp(  hours, 0, 23);
+    clamp(minutes, 0, 59);
+    clamp(seconds, 0, 59);
+
+    current_time  = 1461 * (years / 4);
+    current_time += month_table[month_table_index];
+    current_time += days - 1;
+    current_time *= 86400;
+    current_time += hours * 3600;
+    current_time += minutes * 60;
+    current_time += seconds;
+    current_time *= 1024;
+
+    enable_rtc_interrupts();
+
+  }
+
+  void register_sleeping_thread(
+    uint64_t sleeping_until, application::thread *thread) {
+
+    auto *after = sleeping_threads->first;
+    while (after && after->value.sleeping_until < sleeping_until)
+      after = after->next;
+
+    sleeping_threads->insert_before(
+      { .sleeping_until = sleeping_until, .thread = thread }, after);
+
+  }
+
+  extern "C" void acknowledge_rtc_interrupt();
+
+  extern "C" void on_rtc_interrupt() {
+
+    ++current_time;
+
+    while (sleeping_threads->first &&
+           sleeping_threads->first->value.sleeping_until <=
+             current_time) {
+      application::paused_threads->insert(
+        sleeping_threads->first->value.thread);
+      sleeping_threads->remove(sleeping_threads->first);
+    }
+
+    acknowledge_rtc_interrupt();
+
+  }
+
+}
-- 
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