// SPDX-License-Identifier: GPL-2.0-only
/*
 * Delay loops based on the OpenRISC implementation.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timex.h>

#include <clocksource/arm_arch_timer.h>

#define USECS_TO_CYCLES(time_usecs)                     \
        xloops_to_cycles((time_usecs) * 0x10C7UL)

static inline unsigned long xloops_to_cycles(unsigned long xloops)
{
        return (xloops * loops_per_jiffy * HZ) >> 32;
}

/*
 * Force the use of CNTVCT_EL0 in order to have the same base as WFxT.
 * This avoids some annoying issues when CNTVOFF_EL2 is not reset 0 on a
 * KVM host running at EL1 until we do a vcpu_put() on the vcpu. When
 * running at EL2, the effective offset is always 0.
 *
 * Note that userspace cannot change the offset behind our back either,
 * as the vcpu mutex is held as long as KVM_RUN is in progress.
 */
static cycles_t notrace __delay_cycles(void)
{
        guard(preempt_notrace)();
        return __arch_counter_get_cntvct_stable();
}

void __delay(unsigned long cycles)
{
        cycles_t start = __delay_cycles();

        if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) {
                u64 end = start + cycles;

                /*
                 * Start with WFIT. If an interrupt makes us resume
                 * early, use a WFET loop to complete the delay.
                 */
                wfit(end);
                while ((__delay_cycles() - start) < cycles)
                        wfet(end);
        } else  if (arch_timer_evtstrm_available()) {
                const cycles_t timer_evt_period =
                        USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);

                while ((__delay_cycles() - start + timer_evt_period) < cycles)
                        wfe();
        }

        while ((__delay_cycles() - start) < cycles)
                cpu_relax();
}
EXPORT_SYMBOL(__delay);

inline void __const_udelay(unsigned long xloops)
{
        __delay(xloops_to_cycles(xloops));
}
EXPORT_SYMBOL(__const_udelay);

void __udelay(unsigned long usecs)
{
        __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */
}
EXPORT_SYMBOL(__udelay);

void __ndelay(unsigned long nsecs)
{
        __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */
}
EXPORT_SYMBOL(__ndelay);