86 lines
2.5 KiB
C#
86 lines
2.5 KiB
C#
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///////////////////////////////////////////////////////////////////////////////
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//
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// Microsoft Research Singularity
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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// Note:
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//
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// HalClock is expected to call PMClock's time maintenance
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// functions with a spin lock held.
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//
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namespace Microsoft.Singularity.Hal
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{
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using Microsoft.Singularity.Hal.Acpi;
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using System;
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using System.Diagnostics;
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using System.Threading;
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[ CLSCompliant(false) ]
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internal class HpetClock
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{
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Hpet hpet;
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ulong kernelTicksAccumulated;
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uint hpetLastUpdate;
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internal HpetClock(Hpet timer, ulong initialKernelTicks)
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{
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this.hpet = timer;
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this.hpetLastUpdate = hpet.MainCounterValue32;
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this.kernelTicksAccumulated = initialKernelTicks;
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}
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internal Hpet Hpet
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{
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get { return hpet; }
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}
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[NoHeapAllocation]
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private uint DeltaHpetTicksToKernelTicks(uint delta)
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{
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// Kernel ticks are every 100ns seconds
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ulong t = delta * (ulong)hpet.PeriodFs;
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t /= 100 * 1000 * 1000;
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return (uint) t;
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}
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[NoHeapAllocation]
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internal ulong GetKernelTicks()
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{
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uint now = hpet.MainCounterValue32;
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return (this.kernelTicksAccumulated +
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DeltaHpetTicksToKernelTicks(now - this.hpetLastUpdate)
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);
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}
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[NoHeapAllocation]
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internal void Update()
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{
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uint now = hpet.MainCounterValue32;
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this.kernelTicksAccumulated +=
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DeltaHpetTicksToKernelTicks(now - this.hpetLastUpdate);
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this.hpetLastUpdate = now;
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}
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[NoHeapAllocation]
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public static uint UpdateFrequency(Hpet hpet)
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{
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// Compute RTC clock frequency (2^n Hz) to avoid a
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// wrap between clock interrupts.
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ulong wrapPeriodUs =
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((ulong)0xffffffffu * hpet.PeriodFs) / (1000000 * 1000);
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uint wrapFrequency =
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1 + (uint) ((long)1000000 / (1 + wrapPeriodUs));
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uint updateFrequency = 2; // Min freq of RTC
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while (updateFrequency < 4 * wrapFrequency) {
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updateFrequency *= 2;
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}
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return updateFrequency;
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}
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}
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}
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