| 1 | |
| 2 | |
| 3 | * Delay loops based on the OpenRISC implementation.
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| 4 | *
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| 5 | * Copyright (C) 2012 ARM Limited
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| 6 | *
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| 7 | * Author: Will Deacon <[email protected]>
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| 8 |
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| 9 |
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| 10 | #include <linux/delay.h>
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| 11 | #include <linux/init.h>
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| 12 | #include <linux/kernel.h>
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| 13 | #include <linux/module.h>
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| 14 | #include <linux/timex.h>
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| 15 |
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| 16 | #include <clocksource/arm_arch_timer.h>
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| 17 |
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| 18 | #define USECS_TO_CYCLES(time_usecs) \
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| 19 | xloops_to_cycles((time_usecs) * 0x10C7UL)
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| 20 |
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| 21 | static inline unsigned long xloops_to_cycles(unsigned long xloops)
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| 22 | {
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| 23 | return (xloops * loops_per_jiffy * HZ) >> 32;
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| 24 | }
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| 25 |
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| 26 | |
| 27 | * Force the use of CNTVCT_EL0 in order to have the same base as WFxT.
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| 28 | * This avoids some annoying issues when CNTVOFF_EL2 is not reset 0 on a
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| 29 | * KVM host running at EL1 until we do a vcpu_put() on the vcpu. When
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| 30 | * running at EL2, the effective offset is always 0.
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| 31 | *
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| 32 | * Note that userspace cannot change the offset behind our back either,
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| 33 | * as the vcpu mutex is held as long as KVM_RUN is in progress.
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| 34 |
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| 35 | static cycles_t notrace __delay_cycles(void)
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| 36 | {
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| 37 | guard(preempt_notrace)();
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| 38 | return __arch_counter_get_cntvct_stable();
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| 39 | }
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| 40 |
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| 41 | void __delay(unsigned long cycles)
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| 42 | {
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| 43 | cycles_t start = __delay_cycles();
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| 44 |
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| 45 | if (alternative_has_cap_unlikely(ARM64_HAS_WFXT)) {
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| 46 | u64 end = start + cycles;
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| 47 |
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| 48 | |
| 49 | * Start with WFIT. If an interrupt makes us resume
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| 50 | * early, use a WFET loop to complete the delay.
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| 51 |
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| 52 | wfit(end);
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| 53 | while ((__delay_cycles() - start) < cycles)
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| 54 | wfet(end);
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| 55 | } else if (arch_timer_evtstrm_available()) {
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| 56 | const cycles_t timer_evt_period =
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| 57 | USECS_TO_CYCLES(ARCH_TIMER_EVT_STREAM_PERIOD_US);
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| 58 |
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| 59 | while ((__delay_cycles() - start + timer_evt_period) < cycles)
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| 60 | wfe();
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| 61 | }
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| 62 |
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| 63 | while ((__delay_cycles() - start) < cycles)
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| 64 | cpu_relax();
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| 65 | }
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| 66 | EXPORT_SYMBOL(__delay);
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| 67 |
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| 68 | inline void __const_udelay(unsigned long xloops)
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| 69 | {
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| 70 | __delay(xloops_to_cycles(xloops));
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| 71 | }
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| 72 | EXPORT_SYMBOL(__const_udelay);
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| 73 |
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| 74 | void __udelay(unsigned long usecs)
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| 75 | {
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| 76 | __const_udelay(usecs * 0x10C7UL);
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| 77 | }
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| 78 | EXPORT_SYMBOL(__udelay);
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| 79 |
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| 80 | void __ndelay(unsigned long nsecs)
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| 81 | {
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| 82 | __const_udelay(nsecs * 0x5UL);
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| 83 | }
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| 84 | EXPORT_SYMBOL(__ndelay);
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