delay.c 2.3 KB

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  1. /*
  2. * Delay loops based on the OpenRISC implementation.
  3. *
  4. * Copyright (C) 2012 ARM Limited
  5. *
  6. * This program is free software; you can redistribute it and/or modify
  7. * it under the terms of the GNU General Public License version 2 as
  8. * published by the Free Software Foundation.
  9. *
  10. * This program 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
  13. * GNU General Public License for more details.
  14. *
  15. * You should have received a copy of the GNU General Public License
  16. * along with this program; if not, write to the Free Software
  17. * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18. *
  19. * Author: Will Deacon <will.deacon@arm.com>
  20. */
  21. #include <linux/delay.h>
  22. #include <linux/init.h>
  23. #include <linux/kernel.h>
  24. #include <linux/module.h>
  25. #include <linux/timex.h>
  26. /*
  27. * Default to the loop-based delay implementation.
  28. */
  29. struct arm_delay_ops arm_delay_ops = {
  30. .delay = __loop_delay,
  31. .const_udelay = __loop_const_udelay,
  32. .udelay = __loop_udelay,
  33. };
  34. static const struct delay_timer *delay_timer;
  35. static bool delay_calibrated;
  36. int read_current_timer(unsigned long *timer_val)
  37. {
  38. if (!delay_timer)
  39. return -ENXIO;
  40. *timer_val = delay_timer->read_current_timer();
  41. return 0;
  42. }
  43. static void __timer_delay(unsigned long cycles)
  44. {
  45. cycles_t start = get_cycles();
  46. while ((get_cycles() - start) < cycles)
  47. cpu_relax();
  48. }
  49. static void __timer_const_udelay(unsigned long xloops)
  50. {
  51. unsigned long long loops = xloops;
  52. loops *= loops_per_jiffy;
  53. __timer_delay(loops >> UDELAY_SHIFT);
  54. }
  55. static void __timer_udelay(unsigned long usecs)
  56. {
  57. __timer_const_udelay(usecs * UDELAY_MULT);
  58. }
  59. void __init register_current_timer_delay(const struct delay_timer *timer)
  60. {
  61. if (!delay_calibrated) {
  62. pr_info("Switching to timer-based delay loop\n");
  63. delay_timer = timer;
  64. lpj_fine = timer->freq / HZ;
  65. loops_per_jiffy = lpj_fine;
  66. arm_delay_ops.delay = __timer_delay;
  67. arm_delay_ops.const_udelay = __timer_const_udelay;
  68. arm_delay_ops.udelay = __timer_udelay;
  69. delay_calibrated = true;
  70. } else {
  71. pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
  72. }
  73. }
  74. unsigned long __cpuinit calibrate_delay_is_known(void)
  75. {
  76. delay_calibrated = true;
  77. return lpj_fine;
  78. }