singrdk/base/Drivers/Disk/IdeDisk.sg

//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   IdeDisk.cs
//
//  Base Classes and Interfaces for  ATA Disk devices
//
//  References used:
//  "AT Attachment Interface with Extension (ATA-2)", Revision 4c, DRAFT
//          09/03/97, ISO Working Group T13, http://www.t13.org/
//

// #define DEBUG_LBA48
#define DEBUG_SHARED_IRQ

using System;
using System.Diagnostics;
using Microsoft.SingSharp;
using Microsoft.Contracts;
using System.Threading;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using Microsoft.Singularity.Io;
using System.Runtime.CompilerServices;  //StructAlign attribute
using System.Runtime.InteropServices;   //structLayout attribute
using System.GCs;
using Microsoft.Singularity.V1.Services;
using Microsoft.Singularity.Extending;

using UserAllocation = Microsoft.Singularity.V1.Services.SharedHeapService.Allocation;

namespace Microsoft.Singularity.Drivers.IDE
{
    public enum IdeCmdType
    {
        Read  = 0,
        Write = 1,
    }

    [CLSCompliant(false)]
    public class IdeRequest
    {
        public const int SECTOR_SIZE = 512;

        // [grp] make fields private and add properties??
        // [grp] performance difference should optimize away
        public ulong        SectorNumber;
        //\ public byte* opt(ExHeap[]) Buffer;
        public UIntPtr      BufferOffset;
        /// <summary>Note: This is a pointer into a byte array in the ExHeap.</summary>
        public byte *       BufferAddress;
        public UIntPtr      BufferLength;
        public UIntPtr      Length;
        public IdeCmdType   Command;

        public IdeRequest()
        {
        }

        public void Set(ulong sector,
                        byte* opt(ExHeap[])! buffer,
                        UIntPtr bufferOffset,
                        UIntPtr len,
                        IdeCmdType command)
        {
            this.SectorNumber  = sector;
            //\ this.Buffer        = buffer;
            this.Length        = len;
            this.Command       = command;
            this.BufferOffset  = bufferOffset;

            this.BufferLength  = (UIntPtr)buffer.Length;

            unsafe { this.BufferAddress = (byte*) &buffer[0]; }
        }
    }


#region IdeDisk
    public class IdeDisk
    {
        public const int    MAX_LBA28_SECTOR_COUNT = 256;
        public const int    MAX_LBA48_SECTOR_COUNT = 65536;
        public const byte   IDE_MODE_SET_ULTRA_DMA = 0x40;   // page 176
        public const byte   IDE_FEATURE_SET_TRANSFER_MODE  = 0x03;   // Set the transfer mode.

        private string      deviceName;
        private string      registeredName;   //with Directory
        private string      strDevSel;
        private byte        devsel;
        private bool        atapi;
        private IdentifyDeviceInformation ident;
        private bool        present = false;
        private IdeRequest  ideRequest;
        private IdeConfig   ideConfigHandle;
        private string      ideInstanceName;
        private IdeDiskConfig ideDiskConfig;
        private IdeController controller;
        private int         maxSectorCount;   // [grp] camel case privates?
        private byte        readCommand;
        private byte        writeCommand;
        private int         diskId;
        private static int  diskIdGenerator = 0;
        private static int  connectionCount = 0;

        [CLSCompliant(false)]
        private enum DiskIoEvent : ushort
        {
            Start = 0, // +1 if this is a write // [grp] Seems excessively economical - make explicit?
            End   = 2, // +1 if this is a write
            NewDiskName = 4,
            NewDiskId = 5,
        }

        private class DiskConnectionState
        {
            public const int NoSystemId = 0xffff;   // Whole disk

            private int   systemId;
            private ulong startSector;
            private ulong sectorCount;

            public DiskConnectionState(int sysId, ulong start, ulong count)
            {
                this.systemId    = sysId;
                this.startSector = start;
                this.sectorCount = count;
            }

            public DiskConnectionState(ulong start, ulong count)
            : this(NoSystemId, start, count)
            {
            }

            public DiskAttributes DiskAttributes
            {
                get { return 0; }
            }

            public int SystemId
            {
                get { return this.systemId; }
            }

            public ulong StartSector
            {
                get { return this.startSector; }
            }

            public ulong SectorCount
            {
                get { return this.sectorCount; }
            }
        }

        // TODO: need to set up connection to VolumeManager

        // TODO: do we still need ideDiskConfig.DeviceName field,
        // now that this driver no longer needs to know its public name?

        public void Finalize()
        {
            Tracing.Log(Tracing.Debug," Ide Disk: Finalize");
        }

        public void Run([Claims] ExtensionContract.Exp!             extension,
                        [Claims] ServiceProviderContract.Exp:Start! service,
                        [Claims] VolumeManagerContract.Imp:Start!   volman)
        {
            //\ Tracing.Log(Tracing.Debug," Ide Disk: initialize\n");
            this.ideRequest  = new IdeRequest();

            if (!this.present) {
                delete extension;
                delete service;
                delete volman;
                return;
            }

            this.registeredName = this.ideDiskConfig.DeviceName;

            Tracing.Log(Tracing.Debug,"found VolMgr, awaiting Success");
            DebugStub.Print("Waiting for VolMgr to ack.\n");
            switch receive {
                case volman.Success():
                    Tracing.Log(Tracing.Debug,"Should be in ready state");
                    break;
                case volman.ContractNotSupported():
                    Tracing.Log(Tracing.Debug,"volman is not a volume manager");
                    delete extension;
                    delete service;
                    delete volman;
                    return;
                case volman.ChannelClosed() :
                    Tracing.Log(Tracing.Debug,"volman has closed channel");
                    delete extension;
                    delete service;
                    delete volman;
                    return;
            }
            DebugStub.Print("Connected to VolMgr.\n");

            SetUdmaMode();

            // copy disk name to SharedHeap
            Tracing.Log(Tracing.Debug,"Registering disk {0}", this.registeredName);
            assert volman.InState(VolumeManagerContract.Ready.Value);
            if (!this.atapi) {
                // Assume CD - ROM (ie., no MBR, partitions) if Atapi
                volman.SendRegisterDisk(Bitter.FromString2(this.registeredName));
            }

            Tracing.Log(Tracing.Audit, "Starting diskMsgPump.");

            extension.SendSuccess();

            // create a set of all client endpoints connected to the device
            EMap<DiskDeviceContract.Exp:Ready,DiskConnectionState!> clients =
                new EMap<DiskDeviceContract.Exp:Ready,DiskConnectionState!>();

            // These sets will only ever contain one thing, but they are here to
            // save memory, since this avoids boxing these endpoints
            // once per iteration.
            ESet<ServiceProviderContract.Exp:Start> serviceproviders =
                new ESet<ServiceProviderContract.Exp:Start>();
            serviceproviders.Add(service);
            ESet<VolumeManagerContract.Imp:RegisterAck> volumemanagers1 =
                new ESet<VolumeManagerContract.Imp:RegisterAck>();
            volumemanagers1.Add(volman);
            ESet<VolumeManagerContract.Imp:Accept> volumemanagers2 =
                new ESet<VolumeManagerContract.Imp:Accept>();
            ESet<ExtensionContract.Exp:Ready> extensions =
                new ESet<ExtensionContract.Exp:Ready>();
            extensions.Add(extension);

            try {
                for (bool run = true; run;) {
                    switch receive {
                        // Listen for new connections
                        case sp.Connect(candidate) in serviceproviders:
                            DiskDeviceContract.Exp newClient = candidate as DiskDeviceContract.Exp;
                            if (newClient != null) {
                                newClient.SendSuccess();
                                // switching to use lba48 numbers
                                DiskConnectionState! conn = new DiskConnectionState(0, this.ident.MaxLBASectors);
                                clients.Add(newClient, conn);
                                sp.SendAckConnect();
                            }
                            else {
                                sp.SendNackConnect(candidate);
                            }
                            serviceproviders.Add(sp);
                            break;

                        case sp.ChannelClosed() in serviceproviders:
                            delete sp;
                            break;

                            // Listen for client departure
                        case ep.ChannelClosed() in clients~>connState:
                            Tracing.Log(Tracing.Debug, "Client channel closes.");
                            delete ep;
                            //\ IdeDisk.DumpGCStats();
                            break;

                            // Listen for extension parent
                        case ext.Shutdown() in extensions:
                            ext.SendAckShutdown();
                            delete ext;
                            run = false;
                            break;

                        case ext.ChannelClosed() in extensions:
                            delete ext;
                            break;

                            //Listen for messages on Volume Manager
                        case vm.Connect(candidate, systemId, start, count) in volumemanagers2:
                            DiskDeviceContract.Exp newClient = candidate as DiskDeviceContract.Exp;
                            if (newClient != null) {
                                newClient.SendSuccess();
                                DiskConnectionState! conn = new DiskConnectionState(systemId, start, count);
                                clients.Add(newClient,conn);
                                vm.SendAckConnect();
                            }
                            else {
                                vm.SendNakConnect(candidate);
                            }
                            volumemanagers2.Add(vm);
                            break;

                        case vm.ChannelClosed() in volumemanagers2:
                            delete vm;
                            break;

                        case vm.AckRegisterDisk() in volumemanagers1:
                            Tracing.Log(Tracing.Debug,"volman has accepted the disk");
                            // transition vm into Accept state
                            assert vm.InState(VolumeManagerContract.Accept.Value);
                            volumemanagers2.Add(vm);
                            break;

                        case vm.NakRegisterDisk() in volumemanagers1:
                            Tracing.Log(Tracing.Debug,"volman did not want to register our disk");
                            delete vm;
                            break;

                        case vm.ChannelClosed() in volumemanagers1:
                            Tracing.Log(Tracing.Debug,"volman has closed channel");
                            delete vm;
                            break;


                            // Listen for client requests
                        case ep.GetDeviceName()in clients~>connState:
                            char[] in ExHeap blee = Bitter.FromString(GetDeviceName());
                            ep.SendAckGetDeviceName(blee);
                            clients.Add(ep,connState);
                            break;

                        case ep.GetDiskAttributes() in clients~>connState:
                            ep.SendAckGetDiskAttributes(connState.DiskAttributes);
                            clients.Add(ep, connState);
                            break;

                        case ep.GetStartSector() in clients~>connState:
                            ep.SendAckGetStartSector(connState.StartSector);
                            clients.Add(ep, connState);
                            break;

                        case ep.GetSectorCount() in clients~>connState:
                            ep.SendAckGetSectorCount(connState.SectorCount);
                            clients.Add(ep, connState);
                            break;

                        case ep.GetSystemId() in clients~>connState:
                            int systemId = connState.SystemId;
                            if (systemId != DiskConnectionState.NoSystemId) {
                                ep.SendSystemId((byte)systemId);
                            }
                            else {
                                ep.SendNoSystemId();
                            }
                            clients.Add(ep, connState);
                            break;

                        case ep.Write(data, offset, length, sectorId) in clients~>connState:

                            if (data == null) {
                                Tracing.Log(Tracing.Debug,"data buffer is null!!!\n");
                                ep.SendNakWrite();
                            }
                            else if (this.atapi) { // assume CD - ROM
                                Tracing.Log(Tracing.Debug,"can't write to atapi cdrom\n");
                                delete data;
                                ep.SendNakWrite();
                            }
                            else {
                                //byte* addr;
                                //unsafe { addr = (byte*) &data[0]; }

                                Tracing.Log(Tracing.Debug,"write: sector={0} len={1}",sectorId,length);
                                ReadWrite(true, data, offset, length, sectorId, connState);
                                ep.SendAckWrite(data);
                            }
                            clients.Add(ep, connState);
                            Tracing.Log(Tracing.Debug,"write: ends.");
                            break;

                        case ep.NoOp()in clients~>connState:
                            //DebugStub.Break();
                            ep.SendAckNoOp();
                            clients.Add(ep, connState);
                            break;

                        case ep.Read(data, offset, length, sectorId) in clients~>connState:
                            if (data == null) {
                                Tracing.Log(Tracing.Debug,"data buffer is null!!!\n");
                                ep.SendNakRead();
                            }
                            else {
                                //byte* addr;
                                //unsafe { addr = (byte*) &data[0]; }

                                Tracing.Log(Tracing.Debug,"read: sector={0} len={1}", sectorId, length);
                                ReadWrite(false, data, offset, length, sectorId, connState);
                                ep.SendAckRead(data);
                            }

                            clients.Add(ep, connState);
                            Tracing.Log(Tracing.Debug,"read: ends.");
                            break;

                        case ep.ReadPerf(numMB, chunkSize) in clients~>connState:
                        {
                            long cycles;
                            long ticks;
                            ReadPerf(numMB, chunkSize, out cycles, out ticks, connState);
                            ep.SendAckReadPerf(cycles, ticks);
                            clients.Add(ep, connState);
                            break;
                        }

                        // If all else fails....
                        case clients.Empty() && serviceproviders.Empty() && volumemanagers1.Empty() && volumemanagers2.Empty() && extensions.Empty():
                            Tracing.Log(Tracing.Debug, "Disk driver has no more connections");
                            run = false;
                            break;
                    }
                }
            }
            finally {
                Tracing.Log(Tracing.Debug, "diskMsgPump exiting.");
                clients.Dispose();
                serviceproviders.Dispose();
                extensions.Dispose();
                volumemanagers1.Dispose();
                volumemanagers2.Dispose();
            }
        }

        [NotDelayed]
        public IdeDisk(IdeDiskConfig! config, string! instanceName)
        {
            DebugStub.Print("IdeDisk: {0}\n", __arglist(instanceName));

            this.ideDiskConfig = config;
            this.ideInstanceName = instanceName;
            this.ideConfigHandle = config.ControllerConfig;
            this.controller = config.ControllerConfig.IdeController;
            this.devsel = config.DiskNumber;
            this.atapi = config.Atapi;

            if (this.devsel == 0) {
                this.strDevSel = "master";
            }
            else {
                this.strDevSel = "slave";
                this.devsel = ATA6.DriveSelect;
            }

            try {
                this.ident = ATA6.GetDeviceIdentification(this.controller, this.devsel, this.atapi);
            }
            catch {
                Tracing.Log(Tracing.Debug," GetDeviceIdentification failed!\n");
                this.present = false;
                return;
            }

            if (!this.ident.LBASupported) {
                Tracing.Log(Tracing.Debug,"IdeDisk: Device ({0}) missing or does not support LBA.\n",
                            this.controller.ControllerName);
                DebugStub.WriteLine("IdeDisk: Device ({0}) missing or does not support LBA.\n",
                                    __arglist(this.controller.ControllerName));
                this.present = false;
                this.deviceName = String.Format("IdeDisk: Device ({0}) {1} missing or not supported.\n",
                                                this.strDevSel, this.controller.ControllerName);
                return;
            }

            if (this.ident.LBA48Enabled) {
                this.maxSectorCount = MAX_LBA48_SECTOR_COUNT;
                this.readCommand  = (byte) ATA6.IdeCommand.ReadDmaExt;
                this.writeCommand = (byte) ATA6.IdeCommand.WriteDmaExt;
            }
            else {
                this.maxSectorCount = MAX_LBA28_SECTOR_COUNT;
                this.readCommand  = (byte) ATA6.IdeCommand.ReadDmaRetry;
                this.writeCommand = (byte) ATA6.IdeCommand.WriteDmaRetry;
            }
            this.present = true;
            if (this.ident.ModelNumber == "Virtual HD" ||
                this.ident.ModelNumber == "Virtual CD") {
                this.ideDiskConfig.ControllerConfig.BusMasterDma.SetVirtualized();
            }

            this.deviceName = String.Format("IdeDisk {0} ser {1} {2} MB",
                                            this.ident.ModelNumber,
                                            this.ident.SerialNumber,
                                            (this.ident.MaxLBASectors>>11));

            this.diskId = ++IdeDisk.diskIdGenerator;

            announceDrive();

            Monitoring.Log(Monitoring.Provider.DiskIo,
                           (ushort)DiskIoEvent.NewDiskName, instanceName);
            Monitoring.Log(Monitoring.Provider.DiskIo,
                           (ushort)DiskIoEvent.NewDiskId, 0,
                           (uint)this.diskId, 0, 0, 0, 0);
        }

        private void dumpStatus(int start, int now)
        {
            byte        status;
            status      = this.controller.ReadStatusPort();

            // We timed out and the interrupt occurred.  This implies that we did
            // not get scheduled in a timely way.  Note this and keep on going

            if  (start + 1 == now) {
                DebugStub.WriteLine("ideDisk: timeout; status={0:x},expected INT={1}, actual={2}",
                                    __arglist(status, start+1, now));
                DebugStub.WriteLine("ideDisk: timeout; status={0:x},expected INT={1}, actual={2}",
                                    __arglist(status, start+1, now));
                return;
            }

            byte control,  sectorCount;
            ATA6.DebugQueryStatus(this.controller);
            byte bmStatus = this.ideConfigHandle.BusMasterDma.GetStatus();
            Tracing.Log(Tracing.Debug,"BusMaster status={0:x2}\n",(UIntPtr) bmStatus);
            sectorCount = this.controller.ReadSectorCountPort();
            Tracing.Log(Tracing.Debug," status={0:x} count={1:x}",(UIntPtr) status,(UIntPtr) sectorCount);
            DebugStub.Break();
        }

        private void ShowOffsetAndCount()
        {
            byte lbaLow2  = 0;
            byte lbaMid2  = 0;
            byte lbaHigh2 = 0;

            this.controller.WriteControlPort(0);
            byte lbaLow =  this.controller.ReadLBALowPort();
            byte lbaMid =  this.controller.ReadLBAMidPort();
            byte lbaHigh = this.controller.ReadLBAHighPort();

            if (this.ident.LBA48Enabled) {

                // Write High Order Bit to Control Register
                // so we can probe the "previous" elements of the LBA queue
                this.controller.WriteControlPort(ATA6.DeviceControlHOB);
                lbaLow2 =  this.controller.ReadLBALowPort();
                this.controller.WriteControlPort(ATA6.DeviceControlHOB);
                lbaMid2 =  this.controller.ReadLBAMidPort();
                this.controller.WriteControlPort(ATA6.DeviceControlHOB);
                lbaHigh2 = this.controller.ReadLBAHighPort();

                DebugStub.WriteLine("LBA={0:x2},{1:x2},{2:x2}, {3:x2},{4:x2},{5:x2}",
                                    __arglist(lbaHigh2,lbaMid2,lbaLow2,lbaHigh,lbaMid,lbaLow));
            }
        }

        private void IssueOffsetAndCount(ulong SectorOffset,short sectorCount)
        {
            uint sectors = (uint) sectorCount;
            if (sectorCount > this.maxSectorCount) {
                throw new Exception("IDE Disk: too many sectors");
            }
            if (sectorCount == this.maxSectorCount) {
                sectorCount = 0; // read all sectors
            }

            if (this.ident.LBA48Enabled) {
                // 48 bit addresses are formed by pushing 2 sets of values into the
                // LBA registers: See ATA-6 spec and beyond

                this.controller.WriteSectorCountPort ((byte)((sectors >>  8) & 0xff));
                this.controller.WriteLBALowPort ((byte)((SectorOffset >> 24) & 0xff));
                this.controller.WriteLBAMidPort ((byte)((SectorOffset >> 32) & 0xff));
                this.controller.WriteLBAHighPort((byte)((SectorOffset >> 40) & 0xff));

                this.controller.WriteSectorCountPort ((byte)((sectors >>  0) & 0xff));
                this.controller.WriteLBALowPort ((byte)((SectorOffset >>  0) & 0xff));
                this.controller.WriteLBAMidPort ((byte)((SectorOffset >>  8) & 0xff));
                this.controller.WriteLBAHighPort((byte)((SectorOffset >> 16) & 0xff));

                this.controller.WriteDeviceHeadPort((byte)(this.devsel | 0x40 )); //use LBA
            }
            else {
                this.controller.WriteSectorCountPort ((byte)((sectors >>  0) & 0xff));
                this.controller.WriteLBALowPort ((byte)((SectorOffset >>  0) & 0xff));
                this.controller.WriteLBAMidPort ((byte)((SectorOffset >>  8) & 0xff));
                this.controller.WriteLBAHighPort((byte)((SectorOffset >> 16) & 0xff));
                this.controller.WriteDeviceHeadPort((byte)(this.devsel | 0x40 | (byte)(SectorOffset >> 24)));   // [grp] Doesn't (SectorOffset >> 24) collide with devsel (0|1) if Non-Zero?
            }
#if DEBUG_LBA48
            DebugStub.WriteLine("IDE offset={0}, count ={1}",__arglist(SectorOffset,sectors));
            ShowOffsetAndCount();
#endif
            //Tracing.Log(Tracing.Debug," {0:x} sectorId={1}",(UIntPtr) this.controller.ReadFullStatus(),(UIntPtr)SectorOffset);

        }

        private int ReadPerf(int      numMB,
                             int      chunkSize,
                             out long cycles,
                             out long ticks,
                             DiskConnectionState! conn)
        {
            long endCycles;
            long endClock;
            long startCycles;
            long startClock;

            int sectors = numMB * 1024 * (1024 / IdeRequest.SECTOR_SIZE);
            int sectorsPerChunk = chunkSize / IdeRequest.SECTOR_SIZE;

            byte* opt(ExHeap[]) perfBuffer = new [ExHeap] byte[chunkSize];

            try {
                startCycles = ProcessService.GetCycleCount();
                startClock  = ProcessService.GetUpTime().Ticks;

                int i = 0;
                while (i < sectors) {
                    ReadWrite(false, perfBuffer, 0, (UIntPtr) chunkSize, (ulong)i, conn);
                    i += sectorsPerChunk;
                }

                endCycles = ProcessService.GetCycleCount();
                endClock  = ProcessService.GetUpTime().Ticks;
            }
            finally {
                delete perfBuffer;
            }

            cycles = endCycles - startCycles;
            ticks = endClock - startClock;

            return 0;
        }

        private static ushort evt2ushort(DiskIoEvent evt, bool offset)
        {
            return (ushort)(((ushort)evt) + (offset? 1 : 0));
        }

        private int ReadWrite( bool doWrite,
                               byte[]! in ExHeap  buffer,
                               UIntPtr bufferOffset,
                               UIntPtr length,
                               ulong sector,
                               DiskConnectionState! conn)
        {
            ushort temp;
            ulong sectorId;
            IdeCmdType ideCmdType;
            byte controllerCommand;
            uint dataStart;
            uint bufferStart;

            //if (true) return 0 ;   //use for testing overhead

            // checks
            unsafe {
                bufferStart = (uint)&buffer[0];
                dataStart =  bufferStart + (uint)bufferOffset;

                if ((dataStart & 0x03) != 0) {
                    DebugStub.Break();
                    throw new Exception("IDE ReadWrite: Impermissible buffer (not 4-byte aligned)");
                }
            }

            if ((int)length % IdeRequest.SECTOR_SIZE != 0) {
                DebugStub.Break();
                throw new Exception("IDE ReadWrite: Impermissible buffer (not in sector-size chunks)");
            }

            ulong numSectors = (ulong)length / IdeRequest.SECTOR_SIZE;

            if (sector > conn.SectorCount) {
                throw new Exception("IDE ReadWrite: Sector start out of Bounds.");
            }

            if ((sector + numSectors) > conn.SectorCount) {
                throw new Exception("IDE ReadWrite: Sector operation out of Bounds.");
            }

            sectorId = sector + conn.StartSector;

            if (sectorId >= this.ident.MaxLBASectors) {
                throw new Exception("IDE ReadWrite: Sector out of Bounds.");
            }

            if ((length + bufferOffset) > (UIntPtr)buffer.Length) {
                throw new Exception("IDE ReadWrite: length + offset exceeds array bounds");
            }

            if (length > (UIntPtr) (IdeRequest.SECTOR_SIZE * this.maxSectorCount)) {
                throw new Exception("IDE ReadWrite: Length exceeds MAX_SECTORS");
            }

            // [grp] Reduce branch count w/ Interrupts Off (and total branch count as well).
            if (doWrite) {
                ideCmdType = IdeCmdType.Write;
                controllerCommand = this.writeCommand;
            }
            else {
                ideCmdType = IdeCmdType.Read;
                controllerCommand = this.readCommand;
            }

            //Tracing.Log(Tracing.Debug,"pre cmds {0:x}",
            //            (UIntPtr) this.controller.ReadFullStatus());

            lock (this) {
                if (!this.present) {
                    DebugStub.Break();
                    throw new Exception("IDE ReadWrite: Device Not Present");
                }

                //
                // perform operation
                //
                this.ideRequest.Set((ulong)sectorId,buffer,bufferOffset, length, ideCmdType);

                int startCount;
                bool iflag = PrivilegedGate.DisableInterrupts();
                try {
                    unsafe {
                        Monitoring.Log(Monitoring.Provider.DiskIo,
                                       IdeDisk.evt2ushort(DiskIoEvent.Start, doWrite), 0,
                                       (uint)sectorId, (uint)length, (uint)this.diskId,
                                       (uint)this.ideRequest.BufferAddress, 0);
                    }

                    startCount = DeviceService.GetIrqCount((byte)this.ideConfigHandle.Interrupt.Irq);
                    //Tracing.Log(Tracing.Debug,"pre cmd int={0}",(UIntPtr) startCount);
                    this.controller.SetCommandPending(true);
                    this.controller.SelectDevice(this.devsel, this.atapi); //set master or slave
                    this.controller.PollDRDY(true);            //Wait for Device to indicate ready.

                    this.ideConfigHandle.BusMasterDma.BmPrepareController(this.ideRequest); //setup PRD
                    if (!this.atapi) {
                        this.IssueOffsetAndCount(sectorId,(short) (length >> 9)); //setup LBA
                        this.controller.WriteCommandPort(controllerCommand);
                    }
                    else {
                        this.controller.WriteCommandPort((byte) ATA6.IdeCommand.AtapiPacket);

                        this.controller.WriteFeaturesPort((byte) ATA6.Atapi.DMA);

                        this.controller.WriteLBAHighPort ((byte)(length >> 8));
                        this.controller.WriteLBAMidPort  ((byte)(length >> 0));

                        // set-up the CDB (Command Descriptor Block)

                        byte []cdb; cdb = new byte[10];

                        cdb[0] = (byte)ATA6.Atapi.Read;
                        cdb[1] = 0; // LUN

                        cdb[2] = (byte)(sectorId >> 24);
                        cdb[3] = (byte)(sectorId >> 16);
                        cdb[4] = (byte)(sectorId >>  8);
                        cdb[5] = (byte)(sectorId >>  0);

                        cdb[6] = 0; // Reserved

                        cdb[7] = (byte)(length >> (11 + 8));
                        cdb[8] = (byte)(length >> (11 + 0));

                        cdb[9] = 0; // Control

                        for (int i = 0; i < 10; i += 2) {
                            ushort x = cdb[i+1]; x <<= 8; x |= cdb[i];

                            this.controller.WriteDataPort (x);
                        }
                        this.controller.WriteDataPort (0); // controller needs 12-byte cdb
                    }

                    // DMA protocol Check_Status State
                    // After dma command has been issued the host must read the status register.
                    // Before doing so it must wait 400ns.

                    this.controller.Delay400ns();         // mandatory delay for controller commands

                    //Tracing.Log(Tracing.Debug,"post cmds status={0:x}",
                    //            (UIntPtr) this.controller.ReadFullStatus());

                    this.controller.ReadFullStatus();
                    this.ideConfigHandle.BusMasterDma.Arm(this.ideRequest);

                    //\ ATA6.DebugQueryStatus(this.controller);

                    int currentCount = DeviceService.GetIrqCount((byte)this.ideConfigHandle.Interrupt.Irq);
                    Debug.Assert(currentCount == startCount);
                }
                finally {
                    Tracing.Log(Tracing.Debug, "enabling interrupts for {0}",
                                this.controller.ControllerNameInternal);
                    PrivilegedGate.RestoreInterrupts(iflag);
                }

                bool success = false;
                success = this.ideConfigHandle.CommandEndEvent.WaitOne(TimeSpan.FromMilliseconds(1000));
                int c  = DeviceService.GetIrqCount((byte)this.ideConfigHandle.Interrupt.Irq);
                Tracing.Log(Tracing.Debug,"post wait int={0}, expected={1}",(UIntPtr) c, (uint) (startCount +1) );
#if DEBUG_SHARED_IRQ
                Tracing.Log(Tracing.Debug,"read completes on {0}, numInterrupts={1}\n",
                            this.controller.ControllerNameInternal,
                            (UIntPtr) (c - startCount)
                            );
#endif //DEBUG_SHARED_IRQ

                unsafe {
                    Monitoring.Log(Monitoring.Provider.DiskIo,
                                   IdeDisk.evt2ushort(DiskIoEvent.End, doWrite), 0,
                                   (uint)sectorId, (uint)length, (uint)this.diskId,
                                   (uint)this.ideRequest.BufferAddress, 0);
                }

                if (!success) {
                    dumpStatus(startCount, c);
                }
                if ((c - startCount) != 1) {
                    this.controller.CatchBug = true;
                    this.controller.CatchCount =  (c-startCount);
                    Tracing.Log(Tracing.Debug," ^^^^^^ TRYING To Catch COUNT={0} ^^^^",
                                (UIntPtr) this.controller.CatchCount);
                    //\ DebugStub.Break();
                }
                return 0;
            }
        }

        private static void DumpGCStats()
        {
            int count;
            long millis;
            long bytes;
            GC.PerformanceCounters(out count, out millis, out bytes);
            DebugStub.WriteLine("Disk GC stats - count {0} millis {1} bytes {2}", __arglist(count, millis, bytes));
        }

        private ulong GetSectorCount()
        {
            if (!this.present) {
                throw new Exception("IDE Disk: Device Not Present");
            }
            return this.ident.MaxLBASectors;
        }

        private String GetDeviceName()
        {
            if (!this.present) {
                throw new Exception("IDE Disk: Device Not Present");
            }

            return this.deviceName;
        }

        private void SetUdmaMode()
        {
            if (atapi) {
                return;
            }
            if (!ident.UltraDmaSupported) {
                return;
            }

            this.controller.IssueSet(IdeSet.IDE_SET_MAX_UDMA, ref this.ident);
            this.controller.IssueSet(IdeSet.IDE_SET_READ_AHEAD, ref this.ident);
            // let's see what we get back once we have set it...
            try {
                this.ident = ATA6.GetDeviceIdentification(this.controller, this.devsel, this.atapi);
            }
            catch {
                Tracing.Log(Tracing.Debug, " GetDeviceIdentification failed!\n");
                this.present = false;
                return;
            }
        }

        private void announceDrive()    // [grp] was Parameterized, Why? (ref IdentifyDeviceInformation ident)
        {
            Tracing.Log(Tracing.Debug,"IdeDisk: id {0}, present={1}\n",
                        this.deviceName,
                        (UIntPtr) (this.present ? 1: 0));

            DebugStub.WriteLine("  IdeDisk: id={0}", __arglist(this.deviceName));
            DebugStub.WriteLine("  IdeDisk: {0}" ,__arglist(this.controller.ControllerName));
            DebugStub.WriteLine("  IdeDisk: LBA48={0}, UDMA={1},MaxSectors={2}",
                                __arglist(this.ident.LBA48Enabled,
                                          this.ident.UltraDmaSupported ? this.ident.HighestUltraDmaMode : (byte)0,
                                          this.ident.MaxLBASectors
                                          ));
#if false
            for (ushort i = 8; i > 3; i--) {
                if ((this.ident.MajorVersion & (1 << i)) > 0) {
                    DebugStub.Print("Device supports ATA {0}\n",__arglist(i));
                    break;
                }
            }
#endif
        }
    }
#endregion
}