src/cpu/x86/lapic/apic_timer.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <stdint.h>
   4 #include <console/console.h>
   5 #include <delay.h>
   6 #include <thread.h>
   7 #include <cpu/x86/lapic.h>
   8
   9 void init_timer(void)
  10 {
  11         /* Set the APIC timer to no interrupts and periodic mode */
  12         lapic_write(LAPIC_LVTT, (LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED));
  13
  14         /* Set the divider to 1, no divider */
  15         lapic_write(LAPIC_TDCR, LAPIC_TDR_DIV_1);
  16
  17         /* Set the initial counter to 0xffffffff */
  18         lapic_write(LAPIC_TMICT, 0xffffffff);
  19 }
  20
  21 void udelay(u32 usecs)
  22 {
  23         u32 start, value, ticks, timer_fsb;
  24
  25         if (!thread_yield_microseconds(usecs))
  26                 return;
  27
  28         timer_fsb = get_timer_fsb();
  29         if (!timer_fsb || (lapic_read(LAPIC_LVTT) &
  30                 (LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED)) !=
  31                 (LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED)) {
  32                 init_timer();
  33                 timer_fsb = get_timer_fsb();
  34         }
  35
  36         /* Calculate the number of ticks to run, our FSB runs at timer_fsb MHz
  37          */
  38         ticks = usecs * timer_fsb;
  39         start = lapic_read(LAPIC_TMCCT);
  40         do {
  41                 value = lapic_read(LAPIC_TMCCT);
  42         } while ((start - value) < ticks);
  43 }
  44
  45 #if CONFIG(LAPIC_MONOTONIC_TIMER)
  46 #include <timer.h>
  47
  48 static struct monotonic_counter {
  49         int initialized;
  50         struct mono_time time;
  51         uint32_t last_value;
  52 } mono_counter;
  53
  54 void timer_monotonic_get(struct mono_time *mt)
  55 {
  56         uint32_t current_tick;
  57         uint32_t usecs_elapsed;
  58         uint32_t timer_fsb;
  59
  60         if (!mono_counter.initialized) {
  61                 init_timer();
  62                 timer_fsb = get_timer_fsb();
  63                 /* An FSB frequency of 200Mhz provides a 20 second polling
  64                  * interval between timer_monotonic_get() calls before wrap
  65                  * around occurs. */
  66                 if (timer_fsb > 200)
  67                         printk(BIOS_WARNING,
  68                                "apic timer freq (%d) may be too fast.\n",
  69                                timer_fsb);
  70                 mono_counter.last_value = lapic_read(LAPIC_TMCCT);
  71                 mono_counter.initialized = 1;
  72         }
  73
  74         timer_fsb = get_timer_fsb();
  75         current_tick = lapic_read(LAPIC_TMCCT);
  76         /* Note that the APIC timer counts down. */
  77         usecs_elapsed = (mono_counter.last_value - current_tick) / timer_fsb;
  78
  79         /* Update current time and tick values only if a full tick occurred. */
  80         if (usecs_elapsed) {
  81                 mono_time_add_usecs(&mono_counter.time, usecs_elapsed);
  82                 mono_counter.last_value = current_tick;
  83         }
  84
  85         /* Save result. */
  86         *mt = mono_counter.time;
  87 }
  88 #endif