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