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}