hw/mips_timer.c

   1 #include "hw.h"
   2 #include "mips.h"
   3 #include "qemu-timer.h"
   4
   5 #define TIMER_FREQ      100 * 1000 * 1000
   6
   7 /* XXX: do not use a global */
   8 uint32_t cpu_mips_get_random (CPUState *env)
   9 {
  10     static uint32_t lfsr = 1;
  11     static uint32_t prev_idx = 0;
  12     uint32_t idx;
  13     /* Don't return same value twice, so get another value */
  14     do {
  15         lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xd0000001u);
  16         idx = lfsr % (env->tlb->nb_tlb - env->CP0_Wired) + env->CP0_Wired;
  17     } while (idx == prev_idx);
  18     prev_idx = idx;
  19     return idx;
  20 }
  21
  22 /* MIPS R4K timer */
  23 uint32_t cpu_mips_get_count (CPUState *env)
  24 {
  25     if (env->CP0_Cause & (1 << CP0Ca_DC))
  26         return env->CP0_Count;
  27     else
  28         return env->CP0_Count +
  29             (uint32_t)muldiv64(qemu_get_clock(vm_clock),
  30                                TIMER_FREQ, ticks_per_sec);
  31 }
  32
  33 static void cpu_mips_timer_update(CPUState *env)
  34 {
  35     uint64_t now, next;
  36     uint32_t wait;
  37
  38     now = qemu_get_clock(vm_clock);
  39     wait = env->CP0_Compare - env->CP0_Count -
  40             (uint32_t)muldiv64(now, TIMER_FREQ, ticks_per_sec);
  41     next = now + muldiv64(wait, ticks_per_sec, TIMER_FREQ);
  42     qemu_mod_timer(env->timer, next);
  43 }
  44
  45 void cpu_mips_store_count (CPUState *env, uint32_t count)
  46 {
  47     if (env->CP0_Cause & (1 << CP0Ca_DC))
  48         env->CP0_Count = count;
  49     else {
  50         /* Store new count register */
  51         env->CP0_Count =
  52             count - (uint32_t)muldiv64(qemu_get_clock(vm_clock),
  53                                        TIMER_FREQ, ticks_per_sec);
  54         /* Update timer timer */
  55         cpu_mips_timer_update(env);
  56     }
  57 }
  58
  59 void cpu_mips_store_compare (CPUState *env, uint32_t value)
  60 {
  61     env->CP0_Compare = value;
  62     if (!(env->CP0_Cause & (1 << CP0Ca_DC)))
  63         cpu_mips_timer_update(env);
  64     if (env->insn_flags & ISA_MIPS32R2)
  65         env->CP0_Cause &= ~(1 << CP0Ca_TI);
  66     qemu_irq_lower(env->irq[(env->CP0_IntCtl >> CP0IntCtl_IPTI) & 0x7]);
  67 }
  68
  69 void cpu_mips_start_count(CPUState *env)
  70 {
  71     cpu_mips_store_count(env, env->CP0_Count);
  72 }
  73
  74 void cpu_mips_stop_count(CPUState *env)
  75 {
  76     /* Store the current value */
  77     env->CP0_Count += (uint32_t)muldiv64(qemu_get_clock(vm_clock),
  78                                          TIMER_FREQ, ticks_per_sec);
  79 }
  80
  81 static void mips_timer_cb (void *opaque)
  82 {
  83     CPUState *env;
  84
  85     env = opaque;
  86 #if 0
  87     qemu_log("%s\n", __func__);
  88 #endif
  89
  90     if (env->CP0_Cause & (1 << CP0Ca_DC))
  91         return;
  92
  93     /* ??? This callback should occur when the counter is exactly equal to
  94        the comparator value.  Offset the count by one to avoid immediately
  95        retriggering the callback before any virtual time has passed.  */
  96     env->CP0_Count++;
  97     cpu_mips_timer_update(env);
  98     env->CP0_Count--;
  99     if (env->insn_flags & ISA_MIPS32R2)
 100         env->CP0_Cause |= 1 << CP0Ca_TI;
 101     qemu_irq_raise(env->irq[(env->CP0_IntCtl >> CP0IntCtl_IPTI) & 0x7]);
 102 }
 103
 104 void cpu_mips_clock_init (CPUState *env)
 105 {
 106     env->timer = qemu_new_timer(vm_clock, &mips_timer_cb, env);
 107     env->CP0_Compare = 0;
 108     cpu_mips_store_count(env, 1);
 109 }