128 lines
3.3 KiB
C++
128 lines
3.3 KiB
C++
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/**
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* =========================================================================
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* File : hpet.cpp
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* Project : 0 A.D.
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* Description : Timer implementation using timeGetTime
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* =========================================================================
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*/
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// license: GPL; see lib/license.txt
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#include "precompiled.h"
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#include "hpet.h"
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#include "lib/sysdep/win/win.h"
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#include "lib/sysdep/win/mahaf.h"
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#include "lib/sysdep/acpi.h"
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#include "lib/bits.h"
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#pragma pack(push, 1)
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struct HpetDescriptionTable
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{
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AcpiTable header;
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u32 eventTimerBlockId;
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AcpiGenericAddress baseAddress;
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u8 sequenceNumber;
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u16 minimumPeriodicTicks;
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u8 attributes;
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};
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struct TickSourceHpet::HpetRegisters
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{
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u64 capabilities;
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u64 reserved1;
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u64 config;
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u64 reserved2;
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u64 interruptStatus;
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u64 reserved3[25];
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u64 counterValue;
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u64 reserved4;
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// .. followed by blocks for timers 0..31
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};
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#pragma pack(pop)
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static const u64 CAP_SIZE64 = BIT64(13);
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static const u64 CONFIG_ENABLE = BIT64(0);
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//-----------------------------------------------------------------------------
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TickSourceHpet::TickSourceHpet()
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{
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// (no need to check return value - valid hpet implies success)
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(void)mahaf_Init();
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(void)acpi_Init();
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const HpetDescriptionTable* hpet = (const HpetDescriptionTable*)acpi_GetTable("HPET");
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if(!hpet)
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throw TickSourceUnavailable("HPET: no ACPI table");
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debug_assert(hpet->baseAddress.addressSpaceId == ACPI_AS_MEMORY);
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m_hpetRegisters = (volatile HpetRegisters*)mahaf_MapPhysicalMemory(hpet->baseAddress.address, sizeof(HpetRegisters));
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if(!m_hpetRegisters)
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throw TickSourceUnavailable("HPET: map failed");
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// get counter parameters
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const u64 caps = m_hpetRegisters->capabilities;
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const u32 timerPeriod_fs = bits64(caps, 32, 63);
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m_frequency = 1e15 / timerPeriod_fs;
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m_counterBits = (caps & CAP_SIZE64)? 64 : 32;
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// start the counter (if not already running)
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// note: do not reset value to 0 to avoid interfering with any
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// other users of the timer (e.g. Vista QPC)
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m_hpetRegisters->config |= CONFIG_ENABLE;
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}
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TickSourceHpet::~TickSourceHpet()
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{
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mahaf_UnmapPhysicalMemory((void*)m_hpetRegisters);
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mahaf_Shutdown();
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acpi_Shutdown();
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}
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bool TickSourceHpet::IsSafe() const
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{
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return false;
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// the HPET being created to address other timers' problems, it has
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// no issues of its own.
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return true;
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}
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u64 TickSourceHpet::Ticks() const
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{
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u64 ticks = m_hpetRegisters->counterValue;
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// note: the spec allows 32 or 64 bit counters. given the typical
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// frequency of 14.318 MHz, worst case is rollover within 300 s. this is
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// obviously not long enough to never happen more than once, so it must
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// be handled; there is no benefit in using all 64 bits where available.
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//
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// note that limiting ourselves to 32 bits also avoids the potential
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// headache of non-atomic bus reads.
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ticks &= 0xFFFFFFFFu;
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return ticks;
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}
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/**
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* WHRT uses this to ensure the counter (running at nominal frequency)
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* doesn't overflow more than once during CALIBRATION_INTERVAL_MS.
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**/
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uint TickSourceHpet::CounterBits() const
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{
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return 32;
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}
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/**
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* initial measurement of the tick rate. not necessarily correct
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* (e.g. when using TSC: cpu_ClockFrequency isn't exact).
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**/
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double TickSourceHpet::NominalFrequency() const
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{
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return m_frequency;
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}
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