Time (#11)

* WIP: Time syscalls

* Count time from PIT using low tickrate

* Implement realtime

* Implement nanosleep with a tight loop

arch/x86_64/src/device/mod.rs

@@ -1,5 +1,7 @@
+pub mod rtc;
 pub mod serial;
 
 pub unsafe fn init(){
+    rtc::init();
     serial::init();
 }

arch/x86_64/src/device/rtc.rs

@@ -0,0 +1,109 @@
+use io::{Io, Pio};
+use time;
+
+pub fn init() {
+    let mut rtc = Rtc::new();
+    time::START.lock().0 = rtc.time();
+}
+
+fn cvt_bcd(value: usize) -> usize {
+    (value & 0xF) + ((value / 16) * 10)
+}
+
+/// RTC
+pub struct Rtc {
+    addr: Pio<u8>,
+    data: Pio<u8>,
+}
+
+impl Rtc {
+    /// Create new empty RTC
+    pub fn new() -> Self {
+        return Rtc {
+            addr: Pio::<u8>::new(0x70),
+            data: Pio::<u8>::new(0x71),
+        };
+    }
+
+    /// Read
+    unsafe fn read(&mut self, reg: u8) -> u8 {
+        self.addr.write(reg);
+        return self.data.read();
+    }
+
+    /// Wait
+    unsafe fn wait(&mut self) {
+        while self.read(0xA) & 0x80 != 0x80 {}
+        while self.read(0xA) & 0x80 == 0x80 {}
+    }
+
+    /// Get time
+    pub fn time(&mut self) -> u64 {
+        let mut second;
+        let mut minute;
+        let mut hour;
+        let mut day;
+        let mut month;
+        let mut year;
+        let register_b;
+        unsafe {
+            self.wait();
+            second = self.read(0) as usize;
+            minute = self.read(2) as usize;
+            hour = self.read(4) as usize;
+            day = self.read(7) as usize;
+            month = self.read(8) as usize;
+            year = self.read(9) as usize;
+            register_b = self.read(0xB);
+        }
+
+        if register_b & 4 != 4 {
+            second = cvt_bcd(second);
+            minute = cvt_bcd(minute);
+            hour = cvt_bcd(hour & 0x7F) | (hour & 0x80);
+            day = cvt_bcd(day);
+            month = cvt_bcd(month);
+            year = cvt_bcd(year);
+        }
+
+        if register_b & 2 != 2 || hour & 0x80 == 0x80 {
+            hour = ((hour & 0x7F) + 12) % 24;
+        }
+
+        // TODO: Century Register
+        year += 2000;
+
+        // Unix time from clock
+        let mut secs: u64 = (year as u64 - 1970) * 31536000;
+
+        let mut leap_days = (year as u64 - 1972) / 4 + 1;
+        if year % 4 == 0 {
+            if month <= 2 {
+                leap_days -= 1;
+            }
+        }
+        secs += leap_days * 86400;
+
+        match month {
+            2 => secs += 2678400,
+            3 => secs += 5097600,
+            4 => secs += 7776000,
+            5 => secs += 10368000,
+            6 => secs += 13046400,
+            7 => secs += 15638400,
+            8 => secs += 18316800,
+            9 => secs += 20995200,
+            10 => secs += 23587200,
+            11 => secs += 26265600,
+            12 => secs += 28857600,
+            _ => (),
+        }
+
+        secs += (day as u64 - 1) * 86400;
+        secs += hour as u64 * 3600;
+        secs += minute as u64 * 60;
+        secs += second as u64;
+
+        secs
+    }
+}