SDL-1.2/src/timer/yari/SDL_systimer.c

   1 /*
   2     SDL - Simple DirectMedia Layer
   3     Copyright (C) 1997-2006 Sam Lantinga
   4
   5     This library is free software; you can redistribute it and/or
   6     modify it under the terms of the GNU Lesser General Public
   7     License as published by the Free Software Foundation; either
   8     version 2.1 of the License, or (at your option) any later version.
   9
  10     This library is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13     Lesser General Public License for more details.
  14
  15     You should have received a copy of the GNU Lesser General Public
  16     License along with this library; if not, write to the Free Software
  17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18
  19     Sam Lantinga
  20     slouken@libsdl.org
  21 */
  22
  23 /* YARI's minimal timer implementation is based on that from NDS */
  24 #include "SDL_config.h"
  25
  26 #include "SDL_thread.h"
  27 #include "SDL_timer.h"
  28 #include "SDL_error.h"
  29 #include "../SDL_timer_c.h"
  30
  31 uint64_t yari_rdhwr_TSC(void);
  32
  33 static uint32_t scale, counter_overflow;
  34 static uint64_t start_TSC, prev_TSC;
  35
  36 uint32_t mips32_rdhwr_counter(void);
  37 uint32_t mips32_rdhwr_cycles_pr_count(void);
  38
  39
  40 void SDL_StartTicks(void)
  41 {
  42     uint32_t khz_frequency = 50*1000;
  43     uint32_t cycles_pr_count = mips32_rdhwr_cycles_pr_count();
  44     scale = (1ULL << 32) * cycles_pr_count / khz_frequency;
  45     counter_overflow = 0;
  46     start_TSC = mips32_rdhwr_counter();
  47 }
  48
  49 /*
  50  * Get the number of milliseconds since the SDL library
  51  * initialization. Note that this value wraps if the program runs for
  52  * more than ~49 days
  53  */
  54 Uint32 SDL_GetTicks(void)
  55 {
  56     uint64_t t = mips32_rdhwr_counter();
  57
  58     counter_overflow += t < prev_TSC; // Happens practically never
  59     prev_TSC = t;
  60     t += ((uint64_t) counter_overflow << 32) - start_TSC;
  61
  62     return t * scale >> 32;
  63 }
  64
  65 void SDL_Delay(Uint32 delay_ms)
  66 {
  67     Uint32 t0 = SDL_GetTicks();
  68
  69     while (SDL_GetTicks() < t0 + delay_ms)
  70         SDL_PumpEvents(); // Improve responsiveness at the expense of accuracy
  71 }
  72
  73 /* This is only called if the event thread is not running */
  74 int SDL_SYS_TimerInit(void)
  75 {
  76         return 0;
  77 }
  78
  79 void SDL_SYS_TimerQuit(void)
  80 {
  81 }
  82
  83 int SDL_SYS_StartTimer(void)
  84 {
  85         SDL_SetError("Timers not implemented on YARI");
  86         return -1;
  87 }
  88
  89 void SDL_SYS_StopTimer(void)
  90 {
  91 }