projects / mirror_ubuntu-bionic-kernel.git / blame
| Commit | Line | Data |
|---|---|---|
| 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 | ||
| 19 | #include <asm/processor.h> | |
| 20 | #include <asm/delay.h> | |
| 21 | ||
| 22 | #include <asm/special_insns.h> /* for mfctl() */ | |
| 23 | #include <asm/processor.h> /* for boot_cpu_data */ | |
| 24 | ||
| 25 | /* CR16 based delay: */ | |
| 26 | static void __cr16_delay(unsigned long __loops) | |
| 27 | { | |
| 28 | /* | |
| 29 | * Note: Due to unsigned math, cr16 rollovers shouldn't be | |
| 30 | * a problem here. However, on 32 bit, we need to make sure | |
| 31 | * we don't pass in too big a value. The current default | |
| 32 | * value of MAX_UDELAY_MS should help prevent this. | |
| 33 | */ | |
| 34 | u32 bclock, now, loops = __loops; | |
| 35 | int cpu; | |
| 36 | ||
| 37 | preempt_disable(); | |
| 38 | cpu = smp_processor_id(); | |
| 39 | bclock = mfctl(16); | |
| 40 | for (;;) { | |
| 41 | now = mfctl(16); | |
| 42 | if ((now - bclock) >= loops) | |
| 43 | break; | |
| 44 | ||
| 45 | /* Allow RT tasks to run */ | |
| 46 | preempt_enable(); | |
| 47 | asm volatile(" nop\n"); | |
| 48 | barrier(); | |
| 49 | preempt_disable(); | |
| 50 | ||
| 51 | /* | |
| 52 | * It is possible that we moved to another CPU, and | |
| 53 | * since CR16's are per-cpu we need to calculate | |
| 54 | * that. The delay must guarantee that we wait "at | |
| 55 | * least" the amount of time. Being moved to another | |
| 56 | * CPU could make the wait longer but we just need to | |
| 57 | * make sure we waited long enough. Rebalance the | |
| 58 | * counter for this CPU. | |
| 59 | */ | |
| 60 | if (unlikely(cpu != smp_processor_id())) { | |
| 61 | loops -= (now - bclock); | |
| 62 | cpu = smp_processor_id(); | |
| 63 | bclock = mfctl(16); | |
| 64 | } | |
| 65 | } | |
| 66 | preempt_enable(); | |
| 67 | } | |
| 68 | ||
| 69 | ||
| 70 | void __udelay(unsigned long usecs) | |
| 71 | { | |
| 72 | __cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL)); | |
| 73 | } | |
| 74 | EXPORT_SYMBOL(__udelay); |