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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
f6d12eef HD |
2 | /* |
3 | * Precise Delay Loops for parisc | |
4 | * | |
5 | * based on code by: | |
6 | * Copyright (C) 1993 Linus Torvalds | |
7 | * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> | |
8 | * Copyright (C) 2008 Jiri Hladky <hladky _dot_ jiri _at_ gmail _dot_ com> | |
9 | * | |
10 | * parisc implementation: | |
11 | * Copyright (C) 2013 Helge Deller <deller@gmx.de> | |
12 | */ | |
13 | ||
14 | ||
15 | #include <linux/module.h> | |
16 | #include <linux/preempt.h> | |
17 | #include <linux/init.h> | |
18 | ||
f6d12eef | 19 | #include <asm/delay.h> |
f6d12eef HD |
20 | #include <asm/special_insns.h> /* for mfctl() */ |
21 | #include <asm/processor.h> /* for boot_cpu_data */ | |
22 | ||
23 | /* CR16 based delay: */ | |
24 | static void __cr16_delay(unsigned long __loops) | |
25 | { | |
26 | /* | |
27 | * Note: Due to unsigned math, cr16 rollovers shouldn't be | |
28 | * a problem here. However, on 32 bit, we need to make sure | |
29 | * we don't pass in too big a value. The current default | |
30 | * value of MAX_UDELAY_MS should help prevent this. | |
31 | */ | |
32 | u32 bclock, now, loops = __loops; | |
33 | int cpu; | |
34 | ||
35 | preempt_disable(); | |
36 | cpu = smp_processor_id(); | |
37 | bclock = mfctl(16); | |
38 | for (;;) { | |
39 | now = mfctl(16); | |
40 | if ((now - bclock) >= loops) | |
41 | break; | |
42 | ||
43 | /* Allow RT tasks to run */ | |
44 | preempt_enable(); | |
45 | asm volatile(" nop\n"); | |
46 | barrier(); | |
47 | preempt_disable(); | |
48 | ||
49 | /* | |
50 | * It is possible that we moved to another CPU, and | |
51 | * since CR16's are per-cpu we need to calculate | |
52 | * that. The delay must guarantee that we wait "at | |
53 | * least" the amount of time. Being moved to another | |
54 | * CPU could make the wait longer but we just need to | |
55 | * make sure we waited long enough. Rebalance the | |
56 | * counter for this CPU. | |
57 | */ | |
58 | if (unlikely(cpu != smp_processor_id())) { | |
59 | loops -= (now - bclock); | |
60 | cpu = smp_processor_id(); | |
61 | bclock = mfctl(16); | |
62 | } | |
63 | } | |
64 | preempt_enable(); | |
65 | } | |
66 | ||
67 | ||
68 | void __udelay(unsigned long usecs) | |
69 | { | |
70 | __cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL)); | |
71 | } | |
72 | EXPORT_SYMBOL(__udelay); |