/*
- Perhaps make more references to spec in comments

- ATAPI RW

- Remove Buffer alignment check and just do it on every call

- AHCIATAPISetMaxSpeed?
*/

I64 AHCI_DEBUG = FALSE;
U0 AHCIDebugMode(Bool mode=ON)
{
    AHCI_DEBUG = mode;
}

U0 AHCIDebug(I64 port_num)
{
    CAHCIHba    *hba = blkdev.ahci_hba;
    CAHCIPort   *port = &hba->ports[port_num];

    "\n";
    CallerRep;

    "\nAHCI Port: %d", port_num;

    "\nPort Interrupt Status: %b", port->interrupt_status;
    if (Bt(&port->interrupt_status, AHCI_PxIf_CPDS))
        "\n\tCold Port Detect Status";
    if (Bt(&port->interrupt_status, AHCI_PxIf_TFE))
        "\n\tTask File Error";
    if (Bt(&port->interrupt_status, AHCI_PxIf_HBFS))
        "\n\tHost Bus Fatal Error";
    if (Bt(&port->interrupt_status, AHCI_PxIf_HBDS))
        "\n\tHost Bus Data Error";
    if (Bt(&port->interrupt_status, AHCI_PxIf_IFS))
        "\n\tSATA Interface Fatal Error";
    if (Bt(&port->interrupt_status, AHCI_PxIf_INFS))
        "\n\tSATA Interface Non-Fatal Error";
    if (Bt(&port->interrupt_status, AHCI_PxIf_OFS))
        "\n\tOverflow Status (HBA RX bytes > PRDT bytes)";
    "\nPort Command:          %b", port->command;
    "\nPort Command Issue:    %b", port->cmd_issue;
    "\nPort Task File Data:   %b", port->task_file_data;
    if (Bt(&port->task_file_data, AHCI_PxTFDf_STS_ERR))
    {
        "\n\tTask File Data Error";
        "\n\tTask File Data Error Register: %b", port->task_file_data.u8[1];
    }
    "\nPort Interrupt Enable: %b", port->interrupt_enable;
    "\nPort SATA Status:      %b", port->sata_status;
    "\nPort SATA Ctrl:        %b", port->sata_ctrl;
    "\nPort SATA Error:       %b", port->sata_error;
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_I))
        "\n\tRecovered Data Integrity Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_M))
        "\n\tRecovered Communication Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_T))
        "\n\tTransient Data Integrity Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_C))
        "\n\tPersistent Communication Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_P))
        "\n\tSATA Protocol Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_ERR_E))
        "\n\tInternal Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_DIAG_I))
        "\n\tPHY Internal Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_DIAG_C))
        "\n\tLink Layer CRC Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_DIAG_H))
        "\n\tHandshake Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_DIAG_S))
        "\n\tLink Sequence Error";
    if (Bt(&port->sata_error, AHCI_PxSERR_DIAG_T))
        "\n\tTransport State Transition Error";
    "\nPort SATA Active:      %b", port->sata_active;
    "\nPort SATA Notif:       %b", port->sata_notif;

    "\n";

    "\nHBA Capabilities:      %b", hba->caps;
    "\nHBA Interrupt Status:  %b", hba->interrupt_status;
    if (hba->interrupt_status)
        "\n\t(Each set bit is a port with pending interrupt)";
    "\nHBA Ports Implemented: %b", hba->ports_implemented;
    "\nHBA Version:           0x%0X", hba->version;
    "\nHBA Ext Capabilities:  %b", hba->caps_ext;
    if (Bt(&hba->caps_ext, AHCI_CAPSEXTf_BOH))
        "\n\tBIOS/OS Handoff supported.";
    if (Bt(&hba->caps_ext, AHCI_CAPSEXTf_NVMP))
        "\n\tNVMHCI Supported (Non-Volatile Memory Host Controller Interface)";
    "\nHBA BIOS/OS Handoff:   %b", hba->bohc;
    if (Bt(&hba->bohc, AHCI_BOHCf_BOS))
        "\n\tBIOS owns AHCI Controller";
    if (Bt(&hba->bohc, AHCI_BOHCf_BB))
        "\n\tBIOS Busy";

    "\n";

}

I64 AHCILBA48CapacityGet(U16 *id_record)
{//Get capacity of drive, in LBA blocks.
//Capacity is stored in a U64, so we take the shortcut
//and access the U16-indexed ID record as U64 indexed. Zero-based value.
    return (id_record)(U64 *)[ATA_IDENT_LBA48_CAPACITY / 4] - 1;
}

I64 AHCIPortCmdSlotGet(I64 port_num)
{//Get next free command slot in port; if none, throw error.
    I64          i;
    CAHCIPort   *port   = &blkdev.ahci_hba->ports[port_num];
    U32          slots  = port->sata_active | port->cmd_issue;

    for (i = 0; i < blkdev.cmd_slot_count; i++)
    {
        if (!(slots & 1))
            return i;

        slots >>= 1;
    }

    SysErr("AHCI: No empty command slots on port %d!\n", port_num);
    throw('AHCI');
}

I64 AHCIPortSignatureGet(I64 port_num)
{
    CAHCIPort *port;

    if (port_num < 0 || port_num > AHCI_MAX_PORTS)
        return NULL;

    port = &blkdev.ahci_hba->ports[port_num];
    return port->signature;
}

Bool AHCIPortIsIdle(I64 port_num)
{//Check if the command engine is running on port.
    return !(blkdev.ahci_hba->ports[port_num].command & (AHCI_PxCMDF_ST | AHCI_PxCMDF_CR | AHCI_PxCMDF_FR | AHCI_PxCMDF_FRE));
}

U0 AHCIPortCmdStop(I64 port_num)
{//Stop command engine on port.
    CAHCIPort *port = &blkdev.ahci_hba->ports[port_num];

    Btr(&port->command, AHCI_PxCMDf_ST);
    Btr(&port->command, AHCI_PxCMDf_FRE);

    while (Bt(&port->command, AHCI_PxCMDf_CR) || Bt(&port->command, AHCI_PxCMDf_FR));
}

U0 AHCIPortCmdStart(I64 port_num)
{//Start command engine on port.
    CAHCIPort *port = &blkdev.ahci_hba->ports[port_num];

    while (Bt(&port->command, AHCI_PxCMDf_CR));

    Bts(&port->command, AHCI_PxCMDf_FRE);
    Bts(&port->command, AHCI_PxCMDf_ST);
}

Bool AHCIPortWait(I64 port_num, F64 timeout, Bool throwing=TRUE)
{//Wait until DRQ & BSY are clear in port task file.
    CAHCIPort *port = &blkdev.ahci_hba->ports[port_num];
    U8         str[STR_LEN];

    do
    {
        if (!(port->task_file_data & (ATAS_DRQ | ATAS_BSY)))
            return TRUE;
        Yield; // don't hang OS
    }
    while (timeout > tS);

    if (throwing)
    {
        if (AHCI_DEBUG)
        {
            StrPrint(str, "Run AHCIDebug(%d);", port_num);
            Debug(str);
        }
                    
        SysErr("AHCI: Port %d hung.\n", port_num);
        throw('AHCI');
    }

    return FALSE;
}

U0 AHCIPortReset(I64 port_num)
{//Software reset of port. Port command engine must be started after this.
 //If port is not responsive we do a full reset.
    CAHCIPort *port = &blkdev.ahci_hba->ports[port_num];

    AHCIPortCmdStop(port_num);

    port->interrupt_status = port->interrupt_status; //Acknowledge all interrupt statuses.

    if (!AHCIPortWait(port_num, tS + 1))
    {//Perform 'more intrusive' HBA<->Port comm reset (sec. 10.4.2 of spec).
        port->sata_ctrl = AHCI_PxSCTLF_DET_INIT;
        Sleep(2); //Spec says 1 millisecond
        port->sata_ctrl = 0;
    }

    while (port->sata_status & 0xF != AHCI_PxSSTSF_DET_PRESENT);

    port->sata_error = ~0; //Write all 1s to sata error register.
}

CPortCmdHeader *AHCIPortActiveHeaderGet(I64 port_num, I64 cmd_slot)
{//Get current command slot header on port.
    CAHCIPort       *port = &blkdev.ahci_hba->ports[port_num];
    CPortCmdHeader  *cmd_header = port->cmd_list_base;

    return cmd_header + cmd_slot; //Move up pointer to the slot we have in the command list.
}

U0 AHCIPortCmdWait(I64 port_num, I64 cmd_slot)
{//Wait on command completion after command issue, and double check any error.
    CAHCIPort *port = &blkdev.ahci_hba->ports[port_num];
    U8         str[STR_LEN];

    while (TRUE)
    {
        if (!Bt(&port->cmd_issue, cmd_slot)) //When command has been processed
            break;

        if (Bt(&port->interrupt_status, AHCI_PxIf_TFE)) //Task File Error (ATAS_ERR)
        {
error:
            if (AHCI_DEBUG)
            {
                StrPrint(str, "Run AHCIDebug(%d);", port_num);
                Debug(str);
            }

            SysErr("AHCI: Port %d: Command failed!\n", port_num);
            throw('AHCI');
        }

        Yield; // don't hang OS
    }

    if (Bt(&port->interrupt_status, AHCI_PxIf_TFE)) //Second safety check
        goto error;
}

I64 AHCIAtapiCapacityGet(CBlkDev *bd)
{
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    U32             *buf;

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    buf = CAlloc(8, sys_task->code_heap);

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    //Set up single PRD
    cmd_table->prdt[0].data_base       = buf;
    cmd_table->prdt[0].data_byte_count = DVD_BLK_SIZE - 1; //Zero-based value
    cmd_header->prdt_len = 1;

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;
    cmd_table->acmd[0]  = ATAPI_READ_CAPACITY >> 8;

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return 0;
    }

    return EndianU32(buf[0]);
}

Bool AHCIAtapiSync(CBlkDev *bd)
{ // Sync drive read write buffers.
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;
    cmd_table->acmd[0]  = ATAPI_SYNC_CACHE >> 8;

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }

    return TRUE;
}

Bool AHCIAtapiClose(CBlkDev *bd, I64 close_field=0x200, I64 track=0)
{ // Close track/session on a disc.
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    CAtapiCloseCmd   close_cmd;

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;

    MemSet(&close_cmd, 0, sizeof(CAtapiCloseCmd));
    close_cmd.command   = ATAPI_CLOSE_TRACK_SESSION >> 8;
    close_cmd.code      = close_field.u8[1];
    close_cmd.track_num = EndianU16(track);
    MemCopy(&cmd_table->acmd, &close_cmd, sizeof(CAtapiCloseCmd));

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }

    return TRUE;
}

Bool AHCIAtapiBlank(CBlkDev *bd, Bool minimal=TRUE)
{ // Blank a disc. If minimal set FALSE, entire disc is blanked.
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;
    cmd_table->acmd[0]  = ATAPI_BLANK >> 8;
    cmd_table->acmd[1]  = minimal;

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }

    return TRUE;
}

Bool AHCIAtapiModeWriteSelect(CBlkDev *bd)
{ // Set ATAPI drive write configuration.
    CPortCmdTable           *cmd_table;
    CFisH2D                 *cmd_fis;
    CAHCIPort               *port       = bd->ahci_port;
    I64                      cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader          *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    CAtapiModeWriteList     *mode_list;

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    mode_list = CAlloc(sizeof(CAtapiModeWriteList), sys_task->code_heap);
    mode_list->page.code                = 0x05;         // Write Parameters mode page code
    mode_list->page.length              = 0x32;         // 0x32 indicates no support for Vendor Specific field.
    mode_list->page.type                = 0x00;         // Packet/Incremental mode
    mode_list->page.mode                = 4 | 1 << 5;   // Set CD Track Mode, set Fixed Packet Size bit
    mode_list->page.block_type          = 8;            // Mode 1: 2048-size blocks of data
    mode_list->page.packet_size         = EndianU32(16);// Number of User Data Blocks per Fixed Packet. DVD media default: 16.

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    cmd_table->prdt[0].data_base        = mode_list;
    cmd_table->prdt[0].data_byte_count  = sizeof(CAtapiModeWriteList) - 1; // zero based, size of mode write list
    cmd_header->prdt_len = 1;

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    cmd_fis->feature_low= 0x01; // Core Feature, 'mandatory'
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;
    cmd_table->acmd[0]  = ATAPI_MODE_SELECT >> 8;

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }

    return TRUE;
}

Bool AHCIAtapiStartStop(CBlkDev *bd, Bool start)
{
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');  
    }

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type       = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.
    cmd_fis->command    = ATA_PACKET;
    cmd_table->acmd[0]  = ATAPI_START_STOP_UNIT >> 8;
    cmd_table->acmd[4]  = start;

    AHCIPortWait(bd->port_num, tS + 2);
    Bts(&port->cmd_issue, cmd_slot); //Issue the command.

    try
        AHCIPortCmdWait(bd->port_num, cmd_slot);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }

    return TRUE;
}

Bool DiscEject(U8 drv_let)
{ // returns whether disc tray was successfully ejected.
    try
        return AHCIAtapiStartStop(Letter2BlkDev(drv_let), 2);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }
}

Bool DiscLoad(U8 drv_let)
{ // returns whether disc tray was successfully closed & disc loaded.
    try
        return AHCIAtapiStartStop(Letter2BlkDev(drv_let), 3);
    catch
    {
        Fs->catch_except = TRUE;
        return FALSE;
    }
}

U0 AHCIPortIdentify(CBlkDev *bd)
{//Perform ATA_IDENTIFY command on ATA/ATAPI drive and store capacity and id record.
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port       = bd->ahci_port;
    I64              cmd_slot   = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    U16             *dev_id_record;

    port->interrupt_status = port->interrupt_status; //TODO: Why?

    //Using the code heap for this alloc to stay under 32-bit address space.
    dev_id_record = CAlloc(512, sys_task->code_heap);

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    //Set up single PRD
    cmd_table->prdt[0].data_base       = dev_id_record;
    cmd_table->prdt[0].data_base_upper = 0;
    cmd_table->prdt[0].data_byte_count = 512 - 1; //Zero-based value
    cmd_header->prdt_len = 1; //1 PRD, as described above, which contains the address to put the ID record.

    //Setup command FIS
    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS.

    if (port->signature == AHCI_PxSIG_ATAPI)
        cmd_fis->command = ATA_IDENTIFY_PACKET;
    else
        cmd_fis->command = ATA_IDENTIFY;

    cmd_fis->device  = 0; //No bits need to be set in the device register.

    //Wait on previous command to complete.
    AHCIPortWait(bd->port_num, tS + 2);

    Bts(&port->cmd_issue, cmd_slot); //Issue the command.
    AHCIPortCmdWait(bd->port_num, cmd_slot);

    Free(bd->dev_id_record);
    bd->dev_id_record = dev_id_record;

    if (port->signature == AHCI_PxSIG_ATA)
    {
        bd->max_blk = AHCILBA48CapacityGet(dev_id_record);
        "(Max Block: %d, Disk Size: %d MiB)\n", bd->max_blk, bd->max_blk * BLK_SIZE / 1024 / 1024; 
    }
    else
    {
        bd->max_blk = AHCIAtapiCapacityGet(bd);
        "(Max Block: %d, Disk Size: %d MiB)\n", bd->max_blk, bd->max_blk * DVD_BLK_SIZE / 1024 / 1024; 
    }
}

U8 *AHCIBufferAlign(CBlkDev *bd, U8 *user_buf, I64 buf_size, Bool write)
{//Make sure buffer is accessible by HBA controller.
//Controller requires a U16 aligned buffer and in 32-bit address space (We are not using 64-bit capabilities).
//MAlloc provides U64-aligned addresses, and can allocate in the code heap ( <4GB ).
//In the case of an inadequate buffer address being passed in, we will use a MAlloced internal buffer.
    if(user_buf + buf_size > U32_MAX || user_buf & 1)
    {//if the buffer is not within 32-bit address space or not U16-aligned
//      "Aligning buffer under 32-bit range\n";

        Free(bd->prd_buf);
        bd->prd_buf = MAlloc(buf_size, sys_task->code_heap);

        Bts(&bd->flags, BDf_INTERNAL_BUF);

        if (write)
            MemCopy(bd->prd_buf, user_buf, buf_size);

        return bd->prd_buf;
    }
    Btr(&bd->flags, BDF_INTERNAL_BUF);

    return user_buf;
}

I64 AHCIAtaBlksRW(CBlkDev *bd, U8 *buf, I64 blk, I64 count, Bool write)
{//Read/Write ATA disk blocks. Returns number of bytes transferred between system and disk.
//Don't use this, use the AHCIAtaBlksRead and AHCIAtaBlksWrite functions.
    CPortCmdTable  *cmd_table;
    CFisH2D        *cmd_fis;
    CAHCIPort      *port = bd->ahci_port;
    I64 i, buf_size, buf_size_tmp, byte_count, prdt_len, cmd_slot = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    U8             *internal_buf_tmp, *internal_buf;
    Bool            unlock;

    if (port->signature != AHCI_PxSIG_ATA)
    {
        SysErr("AHCI: Drive is not an ATA drive!\n");
        throw('AHCI');
    }

    if (count < 1) return 0;
    if (count > AHCI_PRDT_MAX_BLOCKS)
    {
        SysErr("AHCI: Block count %d max allowed in one command (%d)", count, AHCI_PRDT_MAX_BLOCKS);
        throw('AHCI');
    }

    unlock = BlkDevLock(bd);

    //Determine buffer size and PRDT length.
    buf_size = buf_size_tmp = count * BLK_SIZE;
    prdt_len = (buf_size - 1) / AHCI_PRD_MAX_BYTES + 1;

//  "PRDT Length:\t%d\n", prdt_len;
//  "Count:\t\t\t%d\n", count;
//  "Buffer size:\t%X\n", buf_size;

    cmd_header->prdt_len = prdt_len; //Set PRD table length in cmd header.
    //Set 'write' bit depending on 'write' argument.
    BEqual(&cmd_header->desc, AHCI_CH_DESCf_W, write);

    internal_buf = internal_buf_tmp = AHCIBufferAlign(bd, buf, buf_size, write);
//  "Buffer:\t\t\t0x%X\n", internal_buf;

    if (!internal_buf) throw('AHCI'); //Will probably never happen.

    //Obtain command table and zero it. This contains the command FIS and the PRDT.
    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));
    
    //Create 'prdt_len' amount of PRD entries in the command table
    for (i = 0; i < prdt_len; i++)
    {//Use max PRD size until the remaining buffer is smaller than max size.
        if (buf_size_tmp > AHCI_PRD_MAX_BYTES)
            byte_count = AHCI_PRD_MAX_BYTES;
        else
            byte_count = buf_size_tmp;

//      "prdt[%d].data_base_addr  = 0x%X\n"  , i, internal_buf_tmp;
//      "prdt[%d].data_byte_count = 0x%X\n\n", i, byte_count;

        cmd_table->prdt[i].data_base = internal_buf_tmp;
        cmd_table->prdt[i].data_byte_count = byte_count - 1; //Zero-based value
        buf_size_tmp -= byte_count;
        internal_buf_tmp += byte_count;
    }
    //Setup the command FIS.
    cmd_fis = cmd_table->cmd_fis;

    cmd_fis->type = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS

    if (write) //Assumed support for LBA48.
        cmd_fis->command = ATA_WRITE_DMA_EXT;
    else
        cmd_fis->command = ATA_READ_DMA_EXT;

    //Fill in the rest of the command FIS.
    cmd_fis->lba0   = blk.u8[0];
    cmd_fis->lba1   = blk.u8[1];
    cmd_fis->lba2   = blk.u8[2];
    cmd_fis->device = 1 << 6; //Required as per ATA8-ACS section 7.25.3
    cmd_fis->lba3   = blk.u8[3];
    cmd_fis->lba4   = blk.u8[4];
    cmd_fis->lba5   = blk.u8[5];
    cmd_fis->count  = count;

    //Wait on previous command to complete.
    AHCIPortWait(bd->port_num, tS + 2);
    //Issue the command.
    Bts(&port->cmd_issue, cmd_slot);
    //Wait on command to finish.
    AHCIPortCmdWait(bd->port_num, cmd_slot);

    if (!write) //If internal_buf was created it back to argument buf.
        if (bd->flags & BDF_INTERNAL_BUF)
        {
//          "Writing back internal buffer\n";
            MemCopy(buf, internal_buf, buf_size);
        }

    if (unlock)
        BlkDevUnlock(bd);

    return cmd_header->prd_byte_count;
}

I64 AHCIAtaBlksRead(CBlkDev *bd, U8 *buf, I64 blk, I64 count)
{//Read 'blk' amount of blocks from AHCI disk device. Returns num of bytes transferred between disk and memory.
    I64 byte_count = 0;
    if (!count)
        return 0;
    if (count <= AHCI_PRDT_MAX_BLOCKS)
    {
//      "$GREEN$READ less than MAX_BLOCKS$FG$\n";
        return AHCIAtaBlksRW(bd, buf, blk, count, FALSE);
    }
    else
    {
//      "$GREEN$READ greater than MAX_BLOCKS\n";
//      "read count: %d\n$FG$", count;
        while (count > AHCI_PRDT_MAX_BLOCKS)
        {
            byte_count += AHCIAtaBlksRW(bd, buf, blk, AHCI_PRDT_MAX_BLOCKS, FALSE);
            count -= AHCI_PRDT_MAX_BLOCKS;
            blk += AHCI_PRDT_MAX_BLOCKS;
            buf += AHCI_PRDT_MAX_BLOCKS * BLK_SIZE;
//          "$GREEN$read count: %d\n$FG$", count;
        }
        byte_count += AHCIAtaBlksRW(bd, buf, blk, count, FALSE);
    }

    blkdev.read_count += (count * bd->blk_size) >> BLK_SIZE_BITS;

    return byte_count;
}

I64 AHCIAtaBlksWrite(CBlkDev *bd, U8 *buf, I64 blk, I64 count)
{//Write 'blk' amount of blocks to AHCI disk device. Returns num of bytes transferred between memory and disk.
    I64  byte_count = 0;

    if (!count)
        return 0;
    if (count <= AHCI_PRDT_MAX_BLOCKS)
    {
//      "$GREEN$WRITE less than MAX_BLOCKS$FG$\n";
        return AHCIAtaBlksRW(bd, buf, blk, count, TRUE);
    }
    else
    {
//      "$GREEN$WRITE greater than MAX_BLOCKS\n";
//      "write count: %d$FG$\n", count;
        while (count > AHCI_PRDT_MAX_BLOCKS)
        {
            byte_count += AHCIAtaBlksRW(bd, buf, blk, AHCI_PRDT_MAX_BLOCKS, TRUE);
            count -= AHCI_PRDT_MAX_BLOCKS;
            blk += AHCI_PRDT_MAX_BLOCKS;
            buf += AHCI_PRDT_MAX_BLOCKS * BLK_SIZE;
//          "$GREEN$write count: %d\n$FG$\n", count;
        }
        byte_count += AHCIAtaBlksRW(bd, buf, blk, count, TRUE);
    }

    return byte_count;
}

I64 AHCIAtapiBlksRead(CBlkDev *bd, U8 *buf, I64 blk, I64 count, Bool lock=TRUE)
{//Read 'blk' amount of blocks from from AHCI ATAPI device. Returns num of bytes transferred.
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port = bd->ahci_port;
    I64              i, byte_count, buf_size, buf_size_tmp, prdt_len, cmd_slot = AHCIPortCmdSlotGet(bd->port_num);
    CPortCmdHeader  *cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);
    U8              *internal_buf, *internal_buf_tmp;
    CAtapiReadCmd    read_cmd;
    Bool             unlock;

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');
    }
    if (count < 1)
        return 0;

    if (lock)
        unlock = BlkDevLock(bd);

    buf_size = buf_size_tmp = count * DVD_BLK_SIZE;
    prdt_len = (buf_size - 1) / AHCI_PRD_MAX_BYTES + 1;

//  "PRDT Length:\t%d\n", prdt_len;
//  "Count:\t\t\t%d\n", count;
//  "Buffer size:\t%X\n", buf_size;

    cmd_header->prdt_len = prdt_len;

    internal_buf = internal_buf_tmp = AHCIBufferAlign(bd, buf, buf_size, FALSE);
//  "Buffer:\t\t\t0x%X\n", internal_buf;

    if (!internal_buf) throw('AHCI');

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A); //Set ATAPI flag in command header

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    for (i = 0; i < prdt_len; i++)
    {
        if (buf_size_tmp > AHCI_PRD_MAX_BYTES) //SHOULD PROBABLY BE ATAPI MAX BYTES
            byte_count = AHCI_PRD_MAX_BYTES;
        else
            byte_count = buf_size_tmp;

//      "prdt[%d].data_base_addr  = 0x%X\n"  , i, internal_buf_tmp;
//      "prdt[%d].data_byte_count = 0x%X\n\n", i, byte_count;
        cmd_table->prdt[i].data_base = internal_buf_tmp;
        cmd_table->prdt[i].data_byte_count = byte_count - 1; //Zero-based value

        buf_size_tmp     -= byte_count;
        internal_buf_tmp += byte_count;
    }

    cmd_fis = cmd_table->cmd_fis;
    MemSet(cmd_fis, 0, sizeof(CFisH2D));

    cmd_fis->type = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS 

    cmd_fis->feature_low = 1; //Necessary?
    cmd_fis->command     = ATA_PACKET;

    MemSet(&read_cmd, 0, sizeof(CAtapiReadCmd));
    read_cmd.command = ATAPI_READ >> 8; //FIX
    read_cmd.lba     = EndianU32(blk);
    read_cmd.count   = EndianU32(count);
    MemCopy(&cmd_table->acmd, &read_cmd, 16);
    
    cmd_fis->count = count; //Necessary?

    AHCIPortWait(bd->port_num, tS + 2);
    
    Bts(&port->cmd_issue, cmd_slot);
    AHCIPortCmdWait(bd->port_num, cmd_slot);
    
    if (bd->flags & BDF_INTERNAL_BUF)
    {
//      "Writing back internal buffer\n";
        MemCopy(buf, internal_buf, buf_size);
    }

    if (lock && unlock)
        BlkDevUnlock(bd);

    return cmd_header->prd_byte_count;
}

I64 AHCIAtapiBlksWrite(CBlkDev *bd, U8 *buf, I64 blk, I64 count, Bool lock=TRUE)
{ // Write blocks to a disc. (AHCIAtapiModeWriteSet must be called first.)
    CPortCmdTable   *cmd_table;
    CFisH2D         *cmd_fis;
    CAHCIPort       *port = bd->ahci_port;
    I64              i, byte_count, buf_size, buf_size_tmp, prdt_len, cmd_slot;
    CPortCmdHeader  *cmd_header;
    U8              *internal_buf, *internal_buf_tmp;
    CAtapiWriteCmd   write_cmd;
    Bool             unlock;

    if (port->signature != AHCI_PxSIG_ATAPI)
    {
        SysErr("AHCI: Drive is not an ATAPI drive!\n");
        throw('AHCI');
    }
    if (count < 1)
        return 0;

    if (lock)
        unlock = BlkDevLock(bd);

    cmd_slot = AHCIPortCmdSlotGet(bd->port_num);
    cmd_header = AHCIPortActiveHeaderGet(bd->port_num, cmd_slot);

    buf_size = buf_size_tmp = count * DVD_BLK_SIZE;
    prdt_len = (buf_size - 1) / AHCI_PRD_MAX_BYTES + 1;

    cmd_header->prdt_len = prdt_len;

    internal_buf = internal_buf_tmp = AHCIBufferAlign(bd, buf, buf_size, TRUE);

    if (!internal_buf) throw('AHCI');

    Bts(&cmd_header->desc, AHCI_CH_DESCf_A); //Set ATAPI flag in command header
    Bts(&cmd_header->desc, AHCI_CH_DESCf_W); //Set WRITE flag in command header

    cmd_table = cmd_header->cmd_table_base;
    MemSet(cmd_table, 0, sizeof(CPortCmdTable));

    for (i = 0; i < prdt_len; i++)
    {
        if (buf_size_tmp > AHCI_PRD_MAX_BYTES)
            byte_count = AHCI_PRD_MAX_BYTES;
        else
            byte_count = buf_size_tmp;
        cmd_table->prdt[i].data_base = internal_buf_tmp;
        cmd_table->prdt[i].data_byte_count = byte_count - 1; //Zero-based value

        buf_size_tmp     -= byte_count;
        internal_buf_tmp += byte_count;
    }

    cmd_fis = cmd_table->cmd_fis;
    MemSet(cmd_fis, 0, sizeof(CFisH2D));

    cmd_fis->type = FISt_H2D;
    Bts(&cmd_fis->desc, AHCI_CF_DESCf_C); //Set Command bit in H2D FIS 

    cmd_fis->command     = ATA_PACKET;

    if (count > U16_MAX) throw('AHCI');
    MemSet(&write_cmd, 0, sizeof(CAtapiWriteCmd));
    write_cmd.command = ATAPI_WRITE >> 8;
    write_cmd.lba    = EndianU32(blk);
    write_cmd.count  = EndianU16(count);
    MemCopy(&cmd_table->acmd, &write_cmd, sizeof(CAtapiWriteCmd));

    AHCIPortWait(bd->port_num, tS + 2);
    
    Bts(&port->cmd_issue, cmd_slot);
    AHCIPortCmdWait(bd->port_num, cmd_slot);
    
    if (bd->flags & BDF_INTERNAL_BUF)
    {
//      "Writing back internal buffer\n";
        MemCopy(buf, internal_buf, buf_size);
    }

    if (lock && unlock)
        BlkDevUnlock(bd);

    return cmd_header->prd_byte_count;
}

U0 AHCIPortInit(CBlkDev *bd, CAHCIPort *port, I64 port_num)
{//Initialize base addresses for command list and FIS receive area and start command execution on port.
    CPortCmdHeader *cmd_header;
    I64             i;

    if (!(port->signature == AHCI_PxSIG_ATAPI || port->signature == AHCI_PxSIG_ATA))
        Debug("AHCI Port/BlkDev error: Invalid Port Signature");

    if (Letter2BlkDevType(bd->first_drive_let) == BDT_ATA && port->signature == AHCI_PxSIG_ATAPI)
        Debug("AHCI Port/BlkDev type mismatch: BlkDev ATA, Port ATAPI");

    if (Letter2BlkDevType(bd->first_drive_let) == BDT_ATAPI && port->signature == AHCI_PxSIG_ATA)
        Debug("AHCI Port/BlkDev type mismatch: BlkDev ATAPI, Port ATA");

    bd->ahci_port = port;
    bd->port_num  = port_num;

    AHCIPortReset(port_num);
    AHCIPortCmdStart(port_num);

    //Spin up, power on device. If the capability isn't suppport the bits will be read-only and this won't do anything.
    port->command |= AHCI_PxCMDF_POD | AHCI_PxCMDF_SUD;
    Sleep(100); //Why?
    AHCIPortCmdStop(port_num);

    //'1K-byte' align as per SATA spec.
    port->cmd_list_base = CAllocAligned(sizeof(CPortCmdHeader) * blkdev.cmd_slot_count, 1024, sys_task->code_heap);
    port->cmd_list_base_upper = 0;

    //Alloc where received FISes will be copied to. '256-byte' align as per spec.
    port->fis_base = CAllocAligned(sizeof(CFisReceived), 256, sys_task->code_heap);
    port->fis_base_upper = 0;

    for (i = 0; i < blkdev.cmd_slot_count; i++)
    {
        cmd_header = &port->cmd_list_base(CPortCmdHeader *)[i];
        //Write Command FIS Length (CFL, a fixed size) in bits 4:0 of the desc. Takes size in U32s.
        cmd_header->desc = sizeof(CFisH2D) / sizeof(U32);

        //'128-byte' align as per SATA spec, minus 1 since length is 1-based.
        cmd_header->cmd_table_base = CAllocAligned(sizeof(CPortCmdTable) + sizeof(CPrdtEntry) * (AHCI_PRDT_MAX_LEN - 1), 128, sys_task->code_heap);
        cmd_header->cmd_table_base_upper = 0;
    }
    AHCIPortCmdStart(port_num);
    AHCIPortIdentify(bd);
}

Bool AHCIAtaInit(CBlkDev *bd)
{
    Bool            unlock, okay = FALSE;
    CPortCmdHeader *cmd_header;
    I64             i;

    if (!bd->ahci_port)
        return FALSE;

    unlock = BlkDevLock(bd);

    // if we re-init a port, keep memory from leaking.
    if (bd->ahci_port->cmd_list_base)
    {
        for (i = 0; i < blkdev.cmd_slot_count; i++)
        {
            cmd_header = &bd->ahci_port->cmd_list_base(CPortCmdHeader *)[i];
            Free(cmd_header->cmd_table_base);
        }
        Free(bd->ahci_port->cmd_list_base);
        Free(bd->ahci_port->fis_base);
    }

    // try to init the port, catch if fails.
    try
    {
        AHCIPortInit(bd, bd->ahci_port, bd->port_num);

        if (bd->type == BDT_ATAPI)
            okay = AHCIAtapiStartStop(bd, TRUE);
        else
            okay = TRUE;
    }
    catch
    {
        Fs->catch_except = TRUE;
        okay = FALSE;
        ST_WARN_ST "AHCIAtaInit";
    }

    if (unlock)
        BlkDevUnlock(bd);

    return okay;
}

U0 AHCIHbaReset()
{
    Bts(&blkdev.ahci_hba->ghc, AHCI_GHCf_HBA_RESET);
    while (Bt(&blkdev.ahci_hba->ghc, AHCI_GHCf_HBA_RESET));
    Bts(&blkdev.ahci_hba->ghc, AHCI_GHCf_AHCI_ENABLE);
}

U0 AHCIInit()
{
    CAHCIHba    *hba;
    CAHCIPort   *port;
    I64          i, bdf;

    "______________________\n";

    bdf = PCIClassFind(PCIC_STORAGE << 16 | PCISC_AHCI << 8 + 1, 0); //0x010601, last byte prog_if, AHCI version 1.0

    if (bdf == -1)
    {
        "AHCI: No AHCI controller found.\n";
        return;
    }

    "AHCI: Controller found\n";
    hba = dev.uncached_alias + PCIReadU32(bdf.u8[2], bdf.u8[1], bdf.u8[0], PCIR_BASE5) & ~0x1F; //Last 4 bits not part of address.
    blkdev.ahci_hba = hba;


    Bts(&blkdev.ahci_hba->ghc, AHCI_GHCf_AHCI_ENABLE);
    "AHCI: GHC.AE set\n";

    //Transferring ownership from BIOS if supported.
    if (Bt(&hba->caps_ext, AHCI_CAPSEXTf_BOH))
    {
        Bts(&hba->bohc, AHCI_BOHCf_OOS);
        "AHCI: Transferring ownership from BIOS\n";

        while (Bt(&hba->bohc, AHCI_BOHCf_BOS));

        Sleep(25);
        if (Bt(&hba->bohc, AHCI_BOHCf_BB)) //if Bios Busy is still set after 25 mS, wait 2 seconds.
            Sleep(2000);
    }

    blkdev.cmd_slot_count = (hba->caps & 0x1F00) >> 8;
    "AHCI: Command slot count: %d\n", blkdev.cmd_slot_count;

    for (i = 0; i < AHCI_MAX_PORTS; i++)
    {
        if (Bt(&hba->ports_implemented, i))
        {//Make ports idle?
            port = &hba->ports[i];
            "AHCI: Port %2d signature 0x%08X ", i, port->signature;
            if (port->signature == AHCI_PxSIG_ATA || port->signature == AHCI_PxSIG_ATAPI)
            {
                if (port->signature == AHCI_PxSIG_ATAPI)
                {
                    Bts(&port->command, AHCI_PxCMDf_ATAPI);
                    "ATAPI drive\n";
                }
                else if (port->signature == AHCI_PxSIG_ATA)
                    "ATA drive\n";

                if (!AHCIPortIsIdle(i))
                {
                    "AHCI: Port %2d not idle, stopping port\n", i;
                    AHCIPortCmdStop(i);
                }
            }
            else
                "Unknown\n";
        }
    }
    "______________________\n\n";
}

Bool AHCIBootDVDProbeAll(CBlkDev *bd)
{
    I64          i;
    CAHCIPort   *port;
    U8          *buf = CAlloc(DVD_BLK_SIZE);
    CKernel     *kernel;

    "______________________\n";

    for (i = 0; i < AHCI_MAX_PORTS; i++)
    {
        if (Bt(&blkdev.ahci_hba->ports_implemented, i))
        {
            port = &blkdev.ahci_hba->ports[i];
            "AHCI: BootDVDProbeAll: Saw port at %2d with signature 0x%0X\n", i, port->signature;

            if (port->signature == AHCI_PxSIG_ATAPI)
            {
                "AHCI: Probing ATAPI drive at port %d\n", i;

                try
                {
                    AHCIPortInit(bd, port, i);

                    AHCIAtapiBlksRead(bd, buf, sys_boot_blk, 1, FALSE);

                    kernel = buf + sys_boot_src.u16[1] << BLK_SIZE_BITS;

                    if (kernel->compile_time == sys_compile_time)
                    {
                        "AHCI: Found sys_compile_time at BLK %d on Port %d\n", sys_boot_blk, i;
                        "______________________\n";
                        return TRUE;
                    }
                    else
                        "AHCI: Did not find matching sys_compile_time on Port %d\n", i;
                }
                catch
                {
                    Fs->catch_except = TRUE;
                    "AHCI: Error at Port %d\n", i;
                }
            }
        }
    }

    Panic("Could not find ATAPI boot drive");

    return FALSE;
}

Bool AHCIAtapiRBlks(CDrive *drive, U8 *buf, I64 blk, I64 count)
{
    CBlkDev *bd         = drive->bd;
    I64      spc        = bd->blk_size >> BLK_SIZE_BITS, n, blk2,
             l2         = bd->max_reads << 1 + spc << 1;
    U8      *dvd_buf;// = MAlloc(l2 << BLK_SIZE_BITS);

    if (bd->type == BDT_ATAPI)
    {
        dvd_buf = MAlloc(l2 << BLK_SIZE_BITS);

        if (blk <= bd->max_reads)
            blk2 = 0;
        else
            blk2 = FloorU64(blk - bd->max_reads, spc);

        if (blk2 + l2 > drive->size + drive->drv_offset)
            l2 = drive->size + drive->drv_offset - blk2;

        n = (l2 + spc - 1) / spc;

//      "AHCIAtapiBlksRead(bd, dvd_buf, %d, %d);", blk2 / spc, n;
        AHCIAtapiBlksRead(bd, dvd_buf, blk2 / spc, n);

        if (bd->flags & BDF_READ_CACHE)
            DiskCacheAdd(drive, dvd_buf, blk2, n * spc);

        MemCopy(buf, dvd_buf + (blk - blk2) << BLK_SIZE_BITS, count << BLK_SIZE_BITS);
        Free(dvd_buf);

    }
    else
        return FALSE;

    return TRUE;
}

Bool AHCIAtaRBlks(CDrive *drive, U8 *buf, I64 blk, I64 count)
{
    CBlkDev *bd = drive->bd;

    if (bd->type == BDT_ATA)
        AHCIAtaBlksRead(bd, buf, blk, count);
    else
        return FALSE;

    return TRUE;
}

Bool AHCIAtaWBlks(CDrive *drive, U8 *buf, I64 blk, I64 count)
{
    CBlkDev *bd = drive->bd;

    AHCIAtaBlksWrite(bd, buf, blk, count);

    blkdev.write_count += count;

    return TRUE;
}