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 
get_timer_value(void)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 
generic_delay_timer_init_args(uint32_t mult,uint32_t div)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 
generic_delay_timer_init(void)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 % 10 == 0) && (div % 10 == 0)) {
53 		mult /= 10;
54 		div /= 10;
55 	}
56 
57 	generic_delay_timer_init_args(mult, div);
58 }
59 
60