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/clocksource.h>
23#include <linux/delay.h>
24#include <linux/init.h>
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/timex.h>
28
29/*
30 * Default to the loop-based delay implementation.
31 */
32struct arm_delay_ops arm_delay_ops = {
33	.delay		= __loop_delay,
34	.const_udelay	= __loop_const_udelay,
35	.udelay		= __loop_udelay,
36};
37
38static const struct delay_timer *delay_timer;
39static bool delay_calibrated;
40static u64 delay_res;
41
42int read_current_timer(unsigned long *timer_val)
43{
44	if (!delay_timer)
45		return -ENXIO;
46
47	*timer_val = delay_timer->read_current_timer();
48	return 0;
49}
50EXPORT_SYMBOL_GPL(read_current_timer);
51
52static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
53{
54	return (cyc * mult) >> shift;
55}
56
57static void __timer_delay(unsigned long cycles)
58{
59	cycles_t start = get_cycles();
60
61	while ((get_cycles() - start) < cycles)
62		cpu_relax();
63}
64
65static void __timer_const_udelay(unsigned long xloops)
66{
67	unsigned long long loops = xloops;
68	loops *= arm_delay_ops.ticks_per_jiffy;
69	__timer_delay(loops >> UDELAY_SHIFT);
70}
71
72static void __timer_udelay(unsigned long usecs)
73{
74	__timer_const_udelay(usecs * UDELAY_MULT);
75}
76
77void __init register_current_timer_delay(const struct delay_timer *timer)
78{
79	u32 new_mult, new_shift;
80	u64 res;
81
82	clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq,
83			       NSEC_PER_SEC, 3600);
84	res = cyc_to_ns(1ULL, new_mult, new_shift);
85
86	if (res > 1000) {
87		pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n",
88			timer, res);
89		return;
90	}
91
92	if (!delay_calibrated && (!delay_res || (res < delay_res))) {
93		pr_info("Switching to timer-based delay loop, resolution %lluns\n", res);
94		delay_timer			= timer;
95		lpj_fine			= timer->freq / HZ;
96		delay_res			= res;
97
98		/* cpufreq may scale loops_per_jiffy, so keep a private copy */
99		arm_delay_ops.ticks_per_jiffy	= lpj_fine;
100		arm_delay_ops.delay		= __timer_delay;
101		arm_delay_ops.const_udelay	= __timer_const_udelay;
102		arm_delay_ops.udelay		= __timer_udelay;
103	} else {
104		pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
105	}
106}
107
108unsigned long calibrate_delay_is_known(void)
109{
110	delay_calibrated = true;
111	return lpj_fine;
112}
113
114void calibration_delay_done(void)
115{
116	delay_calibrated = true;
117}
118