// SPDX-License-Identifier: GPL-2.0 /* * 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/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);