mirror of https://gitee.com/openkylin/linux.git
74 lines
1.8 KiB
C
74 lines
1.8 KiB
C
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/*
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* Precise Delay Loops for parisc
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*
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* based on code by:
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* Copyright (C) 1993 Linus Torvalds
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* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
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* Copyright (C) 2008 Jiri Hladky <hladky _dot_ jiri _at_ gmail _dot_ com>
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*
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* parisc implementation:
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* Copyright (C) 2013 Helge Deller <deller@gmx.de>
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*/
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#include <linux/module.h>
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#include <linux/preempt.h>
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#include <linux/init.h>
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#include <asm/processor.h>
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#include <asm/delay.h>
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#include <asm/special_insns.h> /* for mfctl() */
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#include <asm/processor.h> /* for boot_cpu_data */
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/* CR16 based delay: */
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static void __cr16_delay(unsigned long __loops)
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{
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/*
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* Note: Due to unsigned math, cr16 rollovers shouldn't be
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* a problem here. However, on 32 bit, we need to make sure
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* we don't pass in too big a value. The current default
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* value of MAX_UDELAY_MS should help prevent this.
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*/
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u32 bclock, now, loops = __loops;
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int cpu;
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preempt_disable();
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cpu = smp_processor_id();
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bclock = mfctl(16);
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for (;;) {
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now = mfctl(16);
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if ((now - bclock) >= loops)
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break;
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/* Allow RT tasks to run */
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preempt_enable();
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asm volatile(" nop\n");
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barrier();
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preempt_disable();
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/*
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* It is possible that we moved to another CPU, and
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* since CR16's are per-cpu we need to calculate
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* that. The delay must guarantee that we wait "at
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* least" the amount of time. Being moved to another
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* CPU could make the wait longer but we just need to
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* make sure we waited long enough. Rebalance the
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* counter for this CPU.
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*/
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if (unlikely(cpu != smp_processor_id())) {
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loops -= (now - bclock);
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cpu = smp_processor_id();
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bclock = mfctl(16);
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}
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}
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preempt_enable();
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}
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void __udelay(unsigned long usecs)
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{
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__cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL));
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}
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EXPORT_SYMBOL(__udelay);
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