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comparison src/device/timer.c @ 0:83c23a36980d

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author Tatsuki IHA <e125716@ie.u-ryukyu.ac.jp>
date Fri, 26 May 2017 23:11:05 +0900
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1 // ARM dual-timer module support (SP804)
2 #include "types.h"
3 #include "param.h"
4 #include "arm.h"
5 #include "mmu.h"
6 #include "defs.h"
7 #include "memlayout.h"
8 #include "spinlock.h"
9
10 // A SP804 has two timers, we only use the first one, and as perodic timer
11
12 // define registers (in units of 4-bytes)
13 #define TIMER_LOAD 0 // load register, for perodic timer
14 #define TIMER_CURVAL 1 // current value of the counter
15 #define TIMER_CONTROL 2 // control register
16 #define TIMER_INTCLR 3 // clear (ack) the interrupt (any write clear it)
17 #define TIMER_MIS 5 // masked interrupt status
18
19 // control register bit definitions
20 #define TIMER_ONESHOT 0x01 // wrap or one shot
21 #define TIMER_32BIT 0x02 // 16-bit/32-bit counter
22 #define TIMER_INTEN 0x20 // enable/disable interrupt
23 #define TIMER_PERIODIC 0x40 // enable periodic mode
24 #define TIMER_EN 0x80 // enable the timer
25
26 void isr_timer (struct trapframe *tp, int irq_idx);
27
28 struct spinlock tickslock;
29 uint ticks;
30
31 // acknowledge the timer, write any value to TIMER_INTCLR should do
32 static void ack_timer ()
33 {
34 volatile uint * timer0 = P2V(TIMER0);
35 timer0[TIMER_INTCLR] = 1;
36 }
37
38 // initialize the timer: perodical and interrupt based
39 void timer_init(int hz)
40 {
41 volatile uint * timer0 = P2V(TIMER0);
42
43 initlock(&tickslock, "time");
44
45 timer0[TIMER_LOAD] = CLK_HZ / hz;
46 timer0[TIMER_CONTROL] = TIMER_EN|TIMER_PERIODIC|TIMER_32BIT|TIMER_INTEN;
47
48 pic_enable (PIC_TIMER01, isr_timer);
49 }
50
51 // interrupt service routine for the timer
52 void isr_timer (struct trapframe *tp, int irq_idx)
53 {
54 acquire(&tickslock);
55 ticks++;
56 wakeup(&ticks);
57 release(&tickslock);
58 ack_timer();
59 }
60
61 // a short delay, use timer 1 as the source
62 void micro_delay (int us)
63 {
64 volatile uint * timer1 = P2V(TIMER1);
65
66 // load the initial value to timer1, and configure it to be freerun
67 timer1[TIMER_CONTROL] = TIMER_EN | TIMER_32BIT;
68 timer1[TIMER_LOAD] = us;
69
70 // the register will wrap to 0xFFFFFFFF after decrement to 0
71 while ((int)timer1[TIMER_CURVAL] > 0) {
72
73 }
74
75 // disable timer
76 timer1[TIMER_CONTROL] = 0;
77 }