1 files changed, 152 insertions, 0 deletions
diff --git a/kernel/old/drivers/clock.c b/kernel/old/drivers/clock.c
new file mode 100644
index 0000000..9f3d4be
--- /dev/null
+++ b/kernel/old/drivers/clock.c
@@ -0,0 +1,152 @@
+#define KERNEL_SRC
+
+#include <common.h>
+
+#include <clock.h>
+#include <procs.h>
+
+#include <x86/arch.h>
+#include <x86/pic.h>
+#include <x86/pit.h>
+
+/*
+** PRIVATE DEFINITIONS
+*/
+
+/*
+** PRIVATE DATA TYPES
+*/
+
+/*
+** PRIVATE GLOBAL VARIABLES
+*/
+
+// pinwheel control variables
+static uint32_t pinwheel; // pinwheel counter
+static uint32_t pindex; // index into pinwheel string
+
+/*
+** PUBLIC GLOBAL VARIABLES
+*/
+
+// current system time
+uint32_t system_time;
+
+/*
+** PRIVATE FUNCTIONS
+*/
+
+/**
+** Name:	clk_isr
+**
+** The ISR for the clock
+**
+** @param vector    Vector number for the clock interrupt
+** @param code      Error code (0 for this interrupt)
+*/
+static void clk_isr(int vector, int code)
+{
+	// spin the pinwheel
+
+	++pinwheel;
+	if (pinwheel == (CLOCK_FREQ / 10)) {
+		pinwheel = 0;
+		++pindex;
+		cio_putchar_at(0, 0, "|/-\\"[pindex & 3]);
+	}
+
+#if defined(SYSTEM_STATUS)
+	// Periodically, dump the queue lengths and the SIO status (along
+	// with the SIO buffers, if non-empty).
+	//
+	// Define the symbol SYSTEM_STATUS with a value equal to the desired
+	// reporting frequency, in seconds.
+
+	if ((system_time % SEC_TO_TICKS(SYSTEM_STATUS)) == 0) {
+		cio_printf_at(1, 0, " queues: R[%u] W[%u] S[%u] Z[%u] I[%u]   ",
+					  pcb_queue_length(ready), pcb_queue_length(waiting),
+					  pcb_queue_length(sleeping), pcb_queue_length(zombie),
+					  pcb_queue_length(sioread));
+	}
+#endif
+
+	// time marches on!
+	++system_time;
+
+	// wake up any sleeping processes whose time has come
+	//
+	// we give them preference over the current process when
+	// it is scheduled again
+
+	do {
+		// if there isn't anyone in the sleep queue, we're done
+		if (pcb_queue_empty(sleeping)) {
+			break;
+		}
+
+		// peek at the first member of the queue
+		pcb_t *tmp = pcb_queue_peek(sleeping);
+		assert(tmp != NULL);
+
+		// the sleep queue is sorted in ascending order by wakeup
+		// time, so we know that the retrieved PCB's wakeup time is
+		// the earliest of any process on the sleep queue; if that
+		// time hasn't arrived yet, there's nobody left to awaken
+
+		if (tmp->wakeup > system_time) {
+			break;
+		}
+
+		// OK, we need to wake this process up
+		assert(pcb_queue_remove(sleeping, &tmp) == SUCCESS);
+		schedule(tmp);
+	} while (1);
+
+	// next, we decrement the current process' remaining time
+	current->ticks -= 1;
+
+	// has it expired?
+	if (current->ticks < 1) {
+		// yes! reschedule it
+		schedule(current);
+		current = NULL;
+		// and pick a new process
+		dispatch();
+	}
+
+	// tell the PIC we're done
+	outb(PIC1_CMD, PIC_EOI);
+}
+
+/*
+** PUBLIC FUNCTIONS
+*/
+
+/**
+** Name:  clk_init
+**
+** Initializes the clock module
+**
+*/
+void clk_init(void)
+{
+#if TRACING_INIT
+	cio_puts(" Clock");
+#endif
+
+	// start the pinwheel
+	pinwheel = (CLOCK_FREQ / 10) - 1;
+	pindex = 0;
+
+	// return to the dawn of time
+	system_time = 0;
+
+	// configure the clock
+	uint32_t divisor = PIT_FREQ / CLOCK_FREQ;
+	outb(PIT_CONTROL_PORT, PIT_0_LOAD | PIT_0_SQUARE);
+	outb(PIT_0_PORT, divisor & 0xff); // LSB of divisor
+	outb(PIT_0_PORT, (divisor >> 8) & 0xff); // MSB of divisor
+
+	// register the second-stage ISR
+	install_isr(VEC_TIMER, clk_isr);
+}