reorganize source

[com32] / src / kern / timer.c

diff --git a/src/kern/timer.c b/src/kern/timer.c
new file mode 100644 (file)
index 0000000..c050b84
--- /dev/null
+++ b/src/kern/timer.c
@@ -0,0 +1,192 @@
+/*
+pcboot - bootable PC demo/game kernel
+Copyright (C) 2018-2023 John Tsiombikas <nuclear@member.fsf.org>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY, without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include <stdio.h>
+#include "intr.h"
+#include "asmops.h"
+#include "timer.h"
+#include "panic.h"
+#include "config.h"
+
+/* frequency of the oscillator driving the 8254 timer */
+#define OSC_FREQ_HZ            1193182
+
+/* macro to divide and round to the nearest integer */
+#define DIV_ROUND(a, b) ((a) / (b) + ((a) % (b)) / ((b) / 2))
+
+/* I/O ports connected to the 8254 */
+#define PORT_DATA0     0x40
+#define PORT_DATA1     0x41
+#define PORT_DATA2     0x42
+#define PORT_CMD       0x43
+
+/* command bits */
+#define CMD_CHAN0                      0
+#define CMD_CHAN1                      (1 << 6)
+#define CMD_CHAN2                      (2 << 6)
+#define CMD_RDBACK                     (3 << 6)
+
+#define CMD_LATCH                      0
+#define CMD_ACCESS_LOW         (1 << 4)
+#define CMD_ACCESS_HIGH                (2 << 4)
+#define CMD_ACCESS_BOTH                (3 << 4)
+
+#define CMD_OP_INT_TERM                0
+#define CMD_OP_ONESHOT         (1 << 1)
+#define CMD_OP_RATE                    (2 << 1)
+#define CMD_OP_SQWAVE          (3 << 1)
+#define CMD_OP_SOFT_STROBE     (4 << 1)
+#define CMD_OP_HW_STROBE       (5 << 1)
+
+#define CMD_MODE_BIN           0
+#define CMD_MODE_BCD           1
+
+volatile unsigned long nticks;
+
+struct timer_event {
+       int dt; /* remaining ticks delta from the previous event */
+       void (*func)(void);
+       struct timer_event *next;
+};
+
+static void timer_handler(int inum);
+
+static struct timer_event *evlist;
+
+
+void init_timer(void)
+{
+       /* calculate the reload count: round(osc / freq) */
+       int reload_count = DIV_ROUND(OSC_FREQ_HZ, TICK_FREQ_HZ);
+
+       /* set the mode to square wave for channel 0, both low
+        * and high reload count bytes will follow...
+        */
+       outp(PORT_CMD, CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE);
+
+       /* write the low and high bytes of the reload count to the
+        * port for channel 0
+        */
+       outp(PORT_DATA0, reload_count & 0xff);
+       outp(PORT_DATA0, (reload_count >> 8) & 0xff);
+
+       /* set the timer interrupt handler */
+       interrupt(IRQ_TO_INTR(0), timer_handler);
+       unmask_irq(0);
+}
+
+void cleanup_timer(void)
+{
+       /* return the timer to the original rate */
+       outp(PORT_CMD, CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE);
+       outp(PORT_DATA0, 0);
+       outp(PORT_DATA0, 0);
+}
+
+void set_alarm(unsigned long msec, void (*func)(void))
+{
+       int ticks, tsum, iflag;
+       struct timer_event *ev, *node;
+
+       if((ticks = MSEC_TO_TICKS(msec)) <= 0) {
+               return;
+       }
+
+       if(!(ev = malloc(sizeof *ev))) {
+               panic("failed to allocate timer event");
+               return;
+       }
+       ev->func = func;
+
+       iflag = get_intr_flag();
+       disable_intr();
+
+       if(!evlist || ticks < evlist->dt) {
+               /* insert at the begining */
+               ev->next = evlist;
+               evlist = ev;
+
+               ev->dt = ticks;
+               if(ev->next) {
+                       ev->next->dt -= ticks;
+               }
+       } else {
+               tsum = evlist->dt;
+               node = evlist;
+
+               while(node->next && ticks > tsum + node->next->dt) {
+                       tsum += node->next->dt;
+                       node = node->next;
+               }
+
+               ev->next = node->next;
+               node->next = ev;
+
+               /* fix the relative times */
+               ev->dt = ticks - tsum;
+               if(ev->next) {
+                       ev->next->dt -= ev->dt;
+               }
+       }
+
+       set_intr_flag(iflag);
+}
+
+void cancel_alarm(void (*func)(void))
+{
+       int iflag;
+       struct timer_event *ev, *node;
+       struct timer_event dummy;
+
+       iflag = get_intr_flag();
+       disable_intr();
+
+       dummy.next = evlist;
+       node = &dummy;
+       while(node->next) {
+               ev = node->next;
+               if(ev->func == func) {
+                       /* found it */
+                       if(ev->next) {
+                               ev->next->dt += ev->dt;
+                       }
+                       node->next = ev->next;
+                       free(ev);
+                       break;
+               }
+               node = node->next;
+       }
+
+       set_intr_flag(iflag);
+}
+
+static void timer_handler(int inum)
+{
+       nticks++;
+
+       if(evlist) {
+               evlist->dt--;
+
+               while(evlist && evlist->dt <= 0) {
+                       struct timer_event *ev = evlist;
+                       evlist = evlist->next;
+
+                       ev->func();
+                       free(ev);
+               }
+       }
+}