pmt.cpp

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/* Copyright (c) 2010 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * Timer implementation using ACPI PM timer
 */

#include "precompiled.h"
#include "lib/sysdep/os/win/whrt/pmt.h"

#include "lib/sysdep/os/win/whrt/counter.h"

#include "lib/sysdep/os/win/win.h"
#include "lib/sysdep/acpi.h"
#include "lib/sysdep/os/win/mahaf.h"
#include "lib/bits.h"

static const u32 TMR_VAL_EXT = Bit<u32>(8); // FADT flags

//-----------------------------------------------------------------------------


class CounterPMT : public ICounter
{
public:
    CounterPMT()
        : m_portAddress(0xFFFF)
    {
    }

    virtual const wchar_t* Name() const
    {
        return L"PMT";
    }

    Status Activate()
    {
        // mahaf is needed for port I/O.
        RETURN_STATUS_IF_ERR(mahaf_Init()); // (fails without Administrator privileges)
        // (note: it's called FADT, but the signature is "FACP")
        const FADT* fadt = (const FADT*)acpi_GetTable("FACP");
        if(!fadt)
            return ERR::NOT_SUPPORTED;  // NOWARN (ACPI tables might not be available)
        m_portAddress = u16_from_larger(fadt->pmTimerPortAddress);

        return INFO::OK;
    }

    void Shutdown()
    {
    }

    bool IsSafe() const
    {
        // the PMT has one issue: "Performance counter value may unexpectedly
        // leap forward" (Q274323). This happens on some buggy Pentium-era
        // systems under heavy PCI bus load. We are clever and observe that
        // the TSC implementation would be used on such systems (because it
        // has higher precedence and is safe on P5 CPUs), so the PMT is fine
        // in general.
        return true;
    }

    u64 Counter() const
    {
        return mahaf_ReadPort32(m_portAddress);
    }

    size_t CounterBits() const
    {
        // (see previous acpi_GetTable call)
        const FADT* fadt = (const FADT*)acpi_GetTable("FACP");
        ENSURE(fadt);   // Activate made sure FADT is available
        const size_t counterBits = (fadt->flags & TMR_VAL_EXT)? 32 : 24;
        return counterBits;
    }

    double NominalFrequency() const
    {
        return (double)PMT_FREQ;
    }

    double Resolution() const
    {
        return 1.0 / PMT_FREQ;
    }

private:
    u16 m_portAddress;
};

ICounter* CreateCounterPMT(void* address, size_t size)
{
    ENSURE(sizeof(CounterPMT) <= size);
    return new(address) CounterPMT();
}