drivers/delay_timer/generic_delay_timer.c

   1 /*
   2  * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
   3  *
   4  * SPDX-License-Identifier: BSD-3-Clause
   5  */
   6
   7 #include <arch_helpers.h>
   8 #include <assert.h>
   9 #include <bl_common.h>
  10 #include <debug.h>
  11 #include <delay_timer.h>
  12 #include <generic_delay_timer.h>
  13 #include <platform.h>
  14
  15 /* Ticks elapsed in one second by a signal of 1 MHz */
  16 #define MHZ_TICKS_PER_SEC 1000000
  17
  18 static timer_ops_t ops;
  19
  20 static uint32_t get_timer_value(void)
  21 {
  22         /*
  23          * Generic delay timer implementation expects the timer to be a down
  24          * counter. We apply bitwise NOT operator to the tick values returned
  25          * by read_cntpct_el0() to simulate the down counter. The value is
  26          * clipped from 64 to 32 bits.
  27          */
  28         return (uint32_t)(~read_cntpct_el0());
  29 }
  30
  31 void generic_delay_timer_init_args(uint32_t mult, uint32_t div)
  32 {
  33         ops.get_timer_value     = get_timer_value;
  34         ops.clk_mult            = mult;
  35         ops.clk_div             = div;
  36
  37         timer_init(&ops);
  38
  39         VERBOSE("Generic delay timer configured with mult=%u and div=%u\n",
  40                 mult, div);
  41 }
  42
  43 void generic_delay_timer_init(void)
  44 {
  45         /* Value in ticks */
  46         unsigned int mult = MHZ_TICKS_PER_SEC;
  47
  48         /* Value in ticks per second (Hz) */
  49         unsigned int div  = plat_get_syscnt_freq2();
  50
  51         /* Reduce multiplier and divider by dividing them repeatedly by 10 */
  52         while (((mult % 10U) == 0U) && ((div % 10U) == 0U)) {
  53                 mult /= 10U;
  54                 div /= 10U;
  55         }
  56
  57         generic_delay_timer_init_args(mult, div);
  58 }
  59