hw/openrisc_timer.c

   1 /*
   2  * QEMU OpenRISC timer support
   3  *
   4  * Copyright (c) 2011-2012 Jia Liu <proljc@gmail.com>
   5  *                         Zhizhou Zhang <etouzh@gmail.com>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include "cpu.h"
  22 #include "hw.h"
  23 #include "qemu-timer.h"
  24
  25 #define TIMER_FREQ    (20 * 1000 * 1000)    /* 20MHz */
  26
  27 /* The time when TTCR changes */
  28 static uint64_t last_clk;
  29 static int is_counting;
  30
  31 void cpu_openrisc_count_update(OpenRISCCPU *cpu)
  32 {
  33     uint64_t now, next;
  34     uint32_t wait;
  35
  36     now = qemu_get_clock_ns(vm_clock);
  37     if (!is_counting) {
  38         qemu_del_timer(cpu->env.timer);
  39         last_clk = now;
  40         return;
  41     }
  42
  43     cpu->env.ttcr += (uint32_t)muldiv64(now - last_clk, TIMER_FREQ,
  44                                         get_ticks_per_sec());
  45     last_clk = now;
  46
  47     if ((cpu->env.ttmr & TTMR_TP) <= (cpu->env.ttcr & TTMR_TP)) {
  48         wait = TTMR_TP - (cpu->env.ttcr & TTMR_TP) + 1;
  49         wait += cpu->env.ttmr & TTMR_TP;
  50     } else {
  51         wait = (cpu->env.ttmr & TTMR_TP) - (cpu->env.ttcr & TTMR_TP);
  52     }
  53
  54     next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ);
  55     qemu_mod_timer(cpu->env.timer, next);
  56 }
  57
  58 void cpu_openrisc_count_start(OpenRISCCPU *cpu)
  59 {
  60     is_counting = 1;
  61     cpu_openrisc_count_update(cpu);
  62 }
  63
  64 void cpu_openrisc_count_stop(OpenRISCCPU *cpu)
  65 {
  66     is_counting = 0;
  67     cpu_openrisc_count_update(cpu);
  68 }
  69
  70 static void openrisc_timer_cb(void *opaque)
  71 {
  72     OpenRISCCPU *cpu = opaque;
  73
  74     if ((cpu->env.ttmr & TTMR_IE) &&
  75          qemu_timer_expired(cpu->env.timer, qemu_get_clock_ns(vm_clock))) {
  76         cpu->env.ttmr |= TTMR_IP;
  77         cpu->env.interrupt_request |= CPU_INTERRUPT_TIMER;
  78     }
  79
  80     switch (cpu->env.ttmr & TTMR_M) {
  81     case TIMER_NONE:
  82         break;
  83     case TIMER_INTR:
  84         cpu->env.ttcr = 0;
  85         cpu_openrisc_count_start(cpu);
  86         break;
  87     case TIMER_SHOT:
  88         cpu_openrisc_count_stop(cpu);
  89         break;
  90     case TIMER_CONT:
  91         cpu_openrisc_count_start(cpu);
  92         break;
  93     }
  94 }
  95
  96 void cpu_openrisc_clock_init(OpenRISCCPU *cpu)
  97 {
  98     cpu->env.timer = qemu_new_timer_ns(vm_clock, &openrisc_timer_cb, cpu);
  99     cpu->env.ttmr = 0x00000000;
 100     cpu->env.ttcr = 0x00000000;
 101 }