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
 
22#include <linux/delay.h>
23#include <linux/init.h>
24#include <linux/kernel.h>
25#include <linux/module.h>
26#include <linux/timex.h>
27
28/*
29 * Default to the loop-based delay implementation.
30 */
31struct arm_delay_ops arm_delay_ops = {
32	.delay		= __loop_delay,
33	.const_udelay	= __loop_const_udelay,
34	.udelay		= __loop_udelay,
35};
36
37static const struct delay_timer *delay_timer;
38static bool delay_calibrated;
 
39
40int read_current_timer(unsigned long *timer_val)
41{
42	if (!delay_timer)
43		return -ENXIO;
44
45	*timer_val = delay_timer->read_current_timer();
46	return 0;
47}
48EXPORT_SYMBOL_GPL(read_current_timer);
49
 
 
 
 
 
50static void __timer_delay(unsigned long cycles)
51{
52	cycles_t start = get_cycles();
53
54	while ((get_cycles() - start) < cycles)
55		cpu_relax();
56}
57
58static void __timer_const_udelay(unsigned long xloops)
59{
60	unsigned long long loops = xloops;
61	loops *= arm_delay_ops.ticks_per_jiffy;
62	__timer_delay(loops >> UDELAY_SHIFT);
63}
64
65static void __timer_udelay(unsigned long usecs)
66{
67	__timer_const_udelay(usecs * UDELAY_MULT);
68}
69
70void __init register_current_timer_delay(const struct delay_timer *timer)
71{
72	if (!delay_calibrated) {
73		pr_info("Switching to timer-based delay loop\n");
 
 
 
 
 
 
 
 
 
 
 
 
 
74		delay_timer			= timer;
75		lpj_fine			= timer->freq / HZ;
 
76
77		/* cpufreq may scale loops_per_jiffy, so keep a private copy */
78		arm_delay_ops.ticks_per_jiffy	= lpj_fine;
79		arm_delay_ops.delay		= __timer_delay;
80		arm_delay_ops.const_udelay	= __timer_const_udelay;
81		arm_delay_ops.udelay		= __timer_udelay;
82
83		delay_calibrated		= true;
84	} else {
85		pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
86	}
87}
88
89unsigned long calibrate_delay_is_known(void)
90{
91	delay_calibrated = true;
92	return lpj_fine;
 
 
 
 
 
93}

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Delay loops based on the OpenRISC implementation.
  4 *
  5 * Copyright (C) 2012 ARM Limited
  6 *
 
 
 
 
 
 
 
 
 
 
 
 
 
  7 * Author: Will Deacon <will.deacon@arm.com>
  8 */
  9
 10#include <linux/clocksource.h>
 11#include <linux/delay.h>
 12#include <linux/init.h>
 13#include <linux/kernel.h>
 14#include <linux/module.h>
 15#include <linux/timex.h>
 16
 17/*
 18 * Default to the loop-based delay implementation.
 19 */
 20struct arm_delay_ops arm_delay_ops __ro_after_init = {
 21	.delay		= __loop_delay,
 22	.const_udelay	= __loop_const_udelay,
 23	.udelay		= __loop_udelay,
 24};
 25
 26static const struct delay_timer *delay_timer;
 27static bool delay_calibrated;
 28static u64 delay_res;
 29
 30int read_current_timer(unsigned long *timer_val)
 31{
 32	if (!delay_timer)
 33		return -ENXIO;
 34
 35	*timer_val = delay_timer->read_current_timer();
 36	return 0;
 37}
 38EXPORT_SYMBOL_GPL(read_current_timer);
 39
 40static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
 41{
 42	return (cyc * mult) >> shift;
 43}
 44
 45static void __timer_delay(unsigned long cycles)
 46{
 47	cycles_t start = get_cycles();
 48
 49	while ((get_cycles() - start) < cycles)
 50		cpu_relax();
 51}
 52
 53static void __timer_const_udelay(unsigned long xloops)
 54{
 55	unsigned long long loops = xloops;
 56	loops *= arm_delay_ops.ticks_per_jiffy;
 57	__timer_delay(loops >> UDELAY_SHIFT);
 58}
 59
 60static void __timer_udelay(unsigned long usecs)
 61{
 62	__timer_const_udelay(usecs * UDELAY_MULT);
 63}
 64
 65void __init register_current_timer_delay(const struct delay_timer *timer)
 66{
 67	u32 new_mult, new_shift;
 68	u64 res;
 69
 70	clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq,
 71			       NSEC_PER_SEC, 3600);
 72	res = cyc_to_ns(1ULL, new_mult, new_shift);
 73
 74	if (res > 1000) {
 75		pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n",
 76			timer, res);
 77		return;
 78	}
 79
 80	if (!delay_calibrated && (!delay_res || (res < delay_res))) {
 81		pr_info("Switching to timer-based delay loop, resolution %lluns\n", res);
 82		delay_timer			= timer;
 83		lpj_fine			= timer->freq / HZ;
 84		delay_res			= res;
 85
 86		/* cpufreq may scale loops_per_jiffy, so keep a private copy */
 87		arm_delay_ops.ticks_per_jiffy	= lpj_fine;
 88		arm_delay_ops.delay		= __timer_delay;
 89		arm_delay_ops.const_udelay	= __timer_const_udelay;
 90		arm_delay_ops.udelay		= __timer_udelay;
 
 
 91	} else {
 92		pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
 93	}
 94}
 95
 96unsigned long calibrate_delay_is_known(void)
 97{
 98	delay_calibrated = true;
 99	return lpj_fine;
100}
101
102void calibration_delay_done(void)
103{
104	delay_calibrated = true;
105}