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/delay.h>
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/timex.h>
15
16 #include <clocksource/arm_arch_timer.h>
17
18 #define USECS_TO_CYCLES(time_usecs) \
19 xloops_to_cycles((time_usecs) * 0x10C7UL)
20
21 static inline unsigned long xloops_to_cycles(unsigned long xloops)
22 {
23 return (xloops * loops_per_jiffy * HZ) >> 32;
24 }
25
26 void __delay(unsigned long cycles)
27 {
28 cycles_t start = get_cycles();
29
30 if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) {
31 u64 end = start + cycles;
32
33 /*
34 * Start with WFIT. If an interrupt makes us resume
35 * early, use a WFET loop to complete the delay.
36 */
37 wfit(end);
38 while ((get_cycles() - start) < cycles)
39 wfet(end);
40 } else if (arch_timer_evtstrm_available()) {
41 const cycles_t timer_evt_period =
42 USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
43
44 while ((get_cycles() - start + timer_evt_period) < cycles)
45 wfe();
46 }
47
48 while ((get_cycles() - start) < cycles)
49 cpu_relax();
50 }
51 EXPORT_SYMBOL(__delay);
52
53 inline void __const_udelay(unsigned long xloops)
54 {
55 __delay(xloops_to_cycles(xloops));
56 }
57 EXPORT_SYMBOL(__const_udelay);
58
59 void __udelay(unsigned long usecs)
60 {
61 __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
62 }
63 EXPORT_SYMBOL(__udelay);
64
65 void __ndelay(unsigned long nsecs)
66 {
67 __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
68 }
69 EXPORT_SYMBOL(__ndelay);
70
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