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