localtimer.c 3.3 KB

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  1. /*
  2. * linux/arch/arm/mach-realview/localtimer.c
  3. *
  4. * Copyright (C) 2002 ARM Ltd.
  5. * All Rights Reserved
  6. *
  7. * This program is free software; you can redistribute it and/or modify
  8. * it under the terms of the GNU General Public License version 2 as
  9. * published by the Free Software Foundation.
  10. */
  11. #include <linux/init.h>
  12. #include <linux/kernel.h>
  13. #include <linux/delay.h>
  14. #include <linux/device.h>
  15. #include <linux/smp.h>
  16. #include <linux/jiffies.h>
  17. #include <asm/mach/time.h>
  18. #include <asm/hardware/arm_twd.h>
  19. #include <asm/hardware/gic.h>
  20. #include <asm/hardware.h>
  21. #include <asm/io.h>
  22. #include <asm/irq.h>
  23. #define TWD_BASE(cpu) (__io_address(REALVIEW_TWD_BASE) + \
  24. ((cpu) * REALVIEW_TWD_SIZE))
  25. static unsigned long mpcore_timer_rate;
  26. /*
  27. * local_timer_ack: checks for a local timer interrupt.
  28. *
  29. * If a local timer interrupt has occured, acknowledge and return 1.
  30. * Otherwise, return 0.
  31. */
  32. int local_timer_ack(void)
  33. {
  34. void __iomem *base = TWD_BASE(smp_processor_id());
  35. if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
  36. __raw_writel(1, base + TWD_TIMER_INTSTAT);
  37. return 1;
  38. }
  39. return 0;
  40. }
  41. void __cpuinit local_timer_setup(unsigned int cpu)
  42. {
  43. void __iomem *base = TWD_BASE(cpu);
  44. unsigned int load, offset;
  45. u64 waitjiffies;
  46. unsigned int count;
  47. /*
  48. * If this is the first time round, we need to work out how fast
  49. * the timer ticks
  50. */
  51. if (mpcore_timer_rate == 0) {
  52. printk("Calibrating local timer... ");
  53. /* Wait for a tick to start */
  54. waitjiffies = get_jiffies_64() + 1;
  55. while (get_jiffies_64() < waitjiffies)
  56. udelay(10);
  57. /* OK, now the tick has started, let's get the timer going */
  58. waitjiffies += 5;
  59. /* enable, no interrupt or reload */
  60. __raw_writel(0x1, base + TWD_TIMER_CONTROL);
  61. /* maximum value */
  62. __raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);
  63. while (get_jiffies_64() < waitjiffies)
  64. udelay(10);
  65. count = __raw_readl(base + TWD_TIMER_COUNTER);
  66. mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
  67. printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
  68. (mpcore_timer_rate / 100000) % 100);
  69. }
  70. load = mpcore_timer_rate / HZ;
  71. __raw_writel(load, base + TWD_TIMER_LOAD);
  72. __raw_writel(0x7, base + TWD_TIMER_CONTROL);
  73. /*
  74. * Now maneuver our local tick into the right part of the jiffy.
  75. * Start by working out where within the tick our local timer
  76. * interrupt should go.
  77. */
  78. offset = ((mpcore_timer_rate / HZ) / (NR_CPUS + 1)) * (cpu + 1);
  79. /*
  80. * gettimeoffset() will return a number of us since the last tick.
  81. * Convert this number of us to a local timer tick count.
  82. * Be careful of integer overflow whilst keeping maximum precision.
  83. *
  84. * with HZ=100 and 1MHz (fpga) ~ 1GHz processor:
  85. * load = 1 ~ 10,000
  86. * mpcore_timer_rate/10000 = 100 ~ 100,000
  87. *
  88. * so the multiply value will be less than 10^9 always.
  89. */
  90. load = (system_timer->offset() * (mpcore_timer_rate / 10000)) / 100;
  91. /* Add on our offset to get the load value */
  92. load = (load + offset) % (mpcore_timer_rate / HZ);
  93. __raw_writel(load, base + TWD_TIMER_COUNTER);
  94. /* Make sure our local interrupt controller has this enabled */
  95. __raw_writel(1 << IRQ_LOCALTIMER,
  96. __io_address(REALVIEW_GIC_DIST_BASE) + GIC_DIST_ENABLE_SET);
  97. }
  98. /*
  99. * take a local timer down
  100. */
  101. void __cpuexit local_timer_stop(unsigned int cpu)
  102. {
  103. __raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
  104. }