audk/Omap35xxPkg/MMCHSDxe/MMCHS.c

/** @file

  Copyright (c) 2008-2009, Apple Inc. All rights reserved.
  
  All rights reserved. This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD License
  which accompanies this distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include <Uefi.h>

#include "MMCHS.h"

EFI_BLOCK_IO_MEDIA MMCHSMedia = {
  SIGNATURE_32('s','d','i','o'),            // MediaId
  TRUE,                                     // RemovableMedia
  TRUE,                                     // MediaPresent
  FALSE,                                    // LogicalPartition
  FALSE,                                    // ReadOnly
  FALSE,                                    // WriteCaching
  512,                                      // BlockSize
  4,                                        // IoAlign
  0,                                        // Pad
  0                                         // LastBlock
};

typedef struct {
  VENDOR_DEVICE_PATH  Mmc;
  EFI_DEVICE_PATH     End;
} MMCHS_DEVICE_PATH;

MMCHS_DEVICE_PATH gMmcHsDevicePath = 
{
  {
    HARDWARE_DEVICE_PATH,
    HW_VENDOR_DP,
    (UINT8)(sizeof(VENDOR_DEVICE_PATH)),
    (UINT8)((sizeof(VENDOR_DEVICE_PATH)) >> 8),
    0xb615f1f5, 0x5088, 0x43cd, 0x80, 0x9c, 0xa1, 0x6e, 0x52, 0x48, 0x7d, 0x00 
  },
  {
    END_DEVICE_PATH_TYPE,
    END_ENTIRE_DEVICE_PATH_SUBTYPE,
    sizeof (EFI_DEVICE_PATH_PROTOCOL),
    0
  }
};

CARD_INFO                  *gCardInfo;
EMBEDDED_EXTERNAL_DEVICE   *gTPS65950;

//
// Internal Functions
//

STATIC
VOID
ParseCardCIDData (
  UINT32 Response0, 
  UINT32 Response1, 
  UINT32 Response2,
  UINT32 Response3
  )
{
  gCardInfo->CIDData.MDT = ((Response0 >> 8) & 0xFFF);
  gCardInfo->CIDData.PSN = (((Response0 >> 24) & 0xFF) | ((Response1 & 0xFFFFFF) << 8));
  gCardInfo->CIDData.PRV = ((Response1 >> 24) & 0xFF);
  gCardInfo->CIDData.PNM[4] = ((Response2) & 0xFF);
  gCardInfo->CIDData.PNM[3] = ((Response2 >> 8) & 0xFF);
  gCardInfo->CIDData.PNM[2] = ((Response2 >> 16) & 0xFF);
  gCardInfo->CIDData.PNM[1] = ((Response2 >> 24) & 0xFF);
  gCardInfo->CIDData.PNM[0] = ((Response3) & 0xFF);
  gCardInfo->CIDData.OID = ((Response3 >> 8) & 0xFFFF);
  gCardInfo->CIDData.MID = ((Response3 >> 24) & 0xFF);
}

STATIC
VOID
UpdateMMCHSClkFrequency (
  UINTN NewCLKD
  )
{
  //Set Clock enable to 0x0 to not provide the clock to the card
  MmioAnd32(MMCHS_SYSCTL, ~CEN);

  //Set new clock frequency.
  MmioAndThenOr32(MMCHS_SYSCTL, ~CLKD_MASK, NewCLKD << 6); 

  //Poll till Internal Clock Stable
  while ((MmioRead32(MMCHS_SYSCTL) & ICS_MASK) != ICS);

  //Set Clock enable to 0x1 to provide the clock to the card
  MmioOr32(MMCHS_SYSCTL, CEN);
}

STATIC
EFI_STATUS
SendCmd (
  UINTN Cmd,
  UINTN CmdInterruptEnableVal,
  UINTN CmdArgument
  )
{
  UINTN MmcStatus;
  UINTN RetryCount = 0;

  //Check if command line is in use or not. Poll till command line is available.
  while ((MmioRead32(MMCHS_PSTATE) & DATI_MASK) == DATI_NOT_ALLOWED);

  //Provide the block size.
  MmioWrite32 (MMCHS_BLK, BLEN_512BYTES);

  //Setting Data timeout counter value to max value.
  MmioAndThenOr32(MMCHS_SYSCTL, ~DTO_MASK, DTO_VAL);

  //Clear Status register.
  MmioWrite32 (MMCHS_STAT, 0xFFFFFFFF);

  //Set command argument register
  MmioWrite32 (MMCHS_ARG, CmdArgument);

  //Enable interrupt enable events to occur
  MmioWrite32 (MMCHS_IE, CmdInterruptEnableVal);

  //Send a command
  MmioWrite32 (MMCHS_CMD, Cmd);

  //Check for the command status.
  while (RetryCount < MAX_RETRY_COUNT) {
    do {
      MmcStatus = MmioRead32(MMCHS_STAT);
    } while (MmcStatus == 0);

    //Read status of command response
    if ((MmcStatus & ERRI) != 0) {

      //Perform soft-reset for mmci_cmd line.
      MmioOr32(MMCHS_SYSCTL, SRC);
      while ((MmioRead32(MMCHS_SYSCTL) & SRC));

      DEBUG ((EFI_D_INFO, "MmcStatus: %x\n", MmcStatus));
      return EFI_DEVICE_ERROR;
    }

    //Check if command is completed.
    if ((MmcStatus & CC) == CC) {
      MmioWrite32 (MMCHS_STAT, CC);
      break;
    }

    RetryCount++;
  }

  if (RetryCount == MAX_RETRY_COUNT) {
    return EFI_TIMEOUT;
  }

  return EFI_SUCCESS;
}

STATIC
VOID
GetBlockInformation (
  UINTN *BlockSize,
  UINTN *NumBlocks
  )
{
  CSD_SDV2 *CsdSDV2Data;
  UINTN    CardSize;

  if (gCardInfo->CardType == SD_CARD_2_HIGH) {
    CsdSDV2Data = (CSD_SDV2 *)&gCardInfo->CSDData;

    //Populate BlockSize.
    *BlockSize = (0x1UL << CsdSDV2Data->READ_BL_LEN);

    //Calculate Total number of blocks.
    CardSize = CsdSDV2Data->C_SIZELow16 | (CsdSDV2Data->C_SIZEHigh6 << 2);
    *NumBlocks = ((CardSize + 1) * 1024);
  } else {
    //Populate BlockSize.
    *BlockSize = (0x1UL << gCardInfo->CSDData.READ_BL_LEN);

    //Calculate Total number of blocks.
    CardSize = gCardInfo->CSDData.C_SIZELow2 | (gCardInfo->CSDData.C_SIZEHigh10 << 2);
    *NumBlocks = (CardSize + 1) * (1 << (gCardInfo->CSDData.C_SIZE_MULT + 2));
  }

  //For >=2G card, BlockSize may be 1K, but the transfer size is 512 bytes.
  if (*BlockSize > 512) {
    *NumBlocks = MultU64x32(*NumBlocks, *BlockSize/2);
    *BlockSize = 512;
  }

  DEBUG ((EFI_D_INFO, "Card type: %x, BlockSize: %x, NumBlocks: %x\n", gCardInfo->CardType, *BlockSize, *NumBlocks));
}

STATIC
VOID
CalculateCardCLKD (
  UINTN *ClockFrequencySelect
  )
{
  UINT8    MaxDataTransferRate;
  UINTN    TransferRateValue = 0;
  UINTN    TimeValue = 0 ;
  UINTN    Frequency = 0;

  MaxDataTransferRate = gCardInfo->CSDData.TRAN_SPEED;

  //Calculate Transfer rate unit (Bits 2:0 of TRAN_SPEED)
  switch (MaxDataTransferRate & 0x7) {
    case 0:
      TransferRateValue = 100 * 1000;
      break;

    case 1:
      TransferRateValue = 1 * 1000 * 1000;
      break;

    case 2:
      TransferRateValue = 10 * 1000 * 1000;
      break;

    case 3:
      TransferRateValue = 100 * 1000 * 1000;
      break;

    default:
      DEBUG((EFI_D_ERROR, "Invalid parameter.\n"));
      ASSERT(FALSE);
  }

  //Calculate Time value (Bits 6:3 of TRAN_SPEED)
  switch ((MaxDataTransferRate >> 3) & 0xF) {
    case 1:
      TimeValue = 10;
      break;

    case 2:
      TimeValue = 12;
      break;

    case 3:
      TimeValue = 13;
      break;

    case 4:
      TimeValue = 15;
      break;

    case 5:
      TimeValue = 20;
      break;

    case 6:
      TimeValue = 25;
      break;

    case 7:
      TimeValue = 30;
      break;

    case 8:
      TimeValue = 35;
      break;

    case 9:
      TimeValue = 40;
      break;

    case 10:
      TimeValue = 45;
      break;

    case 11:
      TimeValue = 50;
      break;

    case 12:
      TimeValue = 55;
      break;

    case 13:
      TimeValue = 60;
      break;

    case 14:
      TimeValue = 70;
      break;

    case 15:
      TimeValue = 80;
      break;

    default:
      DEBUG((EFI_D_ERROR, "Invalid parameter.\n"));
      ASSERT(FALSE);
  }

  Frequency = TransferRateValue * TimeValue/10;

  //Calculate Clock divider value to program in MMCHS_SYSCTL[CLKD] field.
  *ClockFrequencySelect = ((MMC_REFERENCE_CLK/Frequency) + 1);

  DEBUG ((EFI_D_INFO, "MaxDataTransferRate: 0x%x, Frequency: %d KHz, ClockFrequencySelect: %x\n", MaxDataTransferRate, Frequency/1000, *ClockFrequencySelect));
}

STATIC
VOID
GetCardConfigurationData (
  VOID
  )
{
  UINTN  BlockSize;
  UINTN  NumBlocks;
  UINTN  ClockFrequencySelect;

  //Calculate BlockSize and Total number of blocks in the detected card.
  GetBlockInformation(&BlockSize, &NumBlocks);
  gCardInfo->BlockSize = BlockSize;
  gCardInfo->NumBlocks = NumBlocks;

  //Calculate Card clock divider value.
  CalculateCardCLKD(&ClockFrequencySelect);
  gCardInfo->ClockFrequencySelect = ClockFrequencySelect;
}

STATIC
EFI_STATUS
InitializeMMCHS (
  VOID
  )
{
  UINT8      Data = 0;
  EFI_STATUS Status;

  //Select Device group to belong to P1 device group in Power IC.
  Data = DEV_GRP_P1;
  Status = gTPS65950->Write(gTPS65950, EXTERNAL_DEVICE_REGISTER(I2C_ADDR_GRP_ID4, VMMC1_DEV_GRP), 1, &Data);
  ASSERT_EFI_ERROR(Status);

  //Configure voltage regulator for MMC1 in Power IC to output 3.0 voltage.
  Data = VSEL_3_00V;
  Status = gTPS65950->Write(gTPS65950, EXTERNAL_DEVICE_REGISTER(I2C_ADDR_GRP_ID4, VMMC1_DEDICATED_REG), 1, &Data);
  ASSERT_EFI_ERROR(Status);
  
  //After ramping up voltage, set VDDS stable bit to indicate that voltage level is stable.
  MmioOr32(CONTROL_PBIAS_LITE, (PBIASLITEVMODE0 | PBIASLITEPWRDNZ0 | PBIASSPEEDCTRL0 | PBIASLITEVMODE1 | PBIASLITEWRDNZ1));

  //Software reset of the MMCHS host controller.
  MmioWrite32 (MMCHS_SYSCONFIG, SOFTRESET);
  gBS->Stall(1000);
  while ((MmioRead32(MMCHS_SYSSTATUS) & RESETDONE_MASK) != RESETDONE);

  //Soft reset for all.
  MmioWrite32 (MMCHS_SYSCTL, SRA);
  gBS->Stall(1000);
  while ((MmioRead32(MMCHS_SYSCTL) & SRA) != 0x0);

  //Voltage capabilities initialization. Activate VS18 and VS30.
  MmioOr32(MMCHS_CAPA, (VS30 | VS18));

  //Wakeup configuration
  MmioOr32(MMCHS_SYSCONFIG, ENAWAKEUP);
  MmioOr32(MMCHS_HCTL, IWE);

  //MMCHS Controller default initialization
  MmioOr32(MMCHS_CON, (OD | DW8_1_4_BIT | CEATA_OFF));

  MmioWrite32 (MMCHS_HCTL, (SDVS_3_0_V | DTW_1_BIT | SDBP_OFF));

  //Enable internal clock
  MmioOr32(MMCHS_SYSCTL, ICE);

  //Set the clock frequency to 80KHz.
  UpdateMMCHSClkFrequency(CLKD_80KHZ);

  //Enable SD bus power.
  MmioOr32(MMCHS_HCTL, (SDBP_ON));

  //Poll till SD bus power bit is set.
  while ((MmioRead32(MMCHS_HCTL) & SDBP_MASK) != SDBP_ON);

  return Status;
}

STATIC
EFI_STATUS
PerformCardIdenfication (
  VOID
  )
{
  EFI_STATUS Status;
  UINTN      CmdArgument = 0;
  UINTN      Response = 0;
  UINTN      RetryCount = 0;
  BOOLEAN    SDCmd8Supported = FALSE;

  //Enable interrupts.
	MmioWrite32 (MMCHS_IE, (BADA_EN | CERR_EN | DEB_EN | DCRC_EN | DTO_EN | CIE_EN |
    CEB_EN | CCRC_EN | CTO_EN | BRR_EN | BWR_EN | TC_EN | CC_EN));

  //Controller INIT procedure start.
  MmioOr32(MMCHS_CON, INIT);
  MmioWrite32 (MMCHS_CMD, 0x00000000);
  while (!(MmioRead32(MMCHS_STAT) & CC));

  //Wait for 1 ms
  gBS->Stall(1000);

  //Set CC bit to 0x1 to clear the flag
  MmioOr32(MMCHS_STAT, CC);

  //Retry INIT procedure.
  MmioWrite32 (MMCHS_CMD, 0x00000000);
  while (!(MmioRead32(MMCHS_STAT) & CC));

  //End initialization sequence
  MmioAnd32(MMCHS_CON, ~INIT);

  MmioOr32(MMCHS_HCTL, (SDVS_3_0_V | DTW_1_BIT | SDBP_ON));

  //Change clock frequency to 400KHz to fit protocol
  UpdateMMCHSClkFrequency(CLKD_400KHZ);

  MmioOr32(MMCHS_CON, OD);

  //Send CMD0 command.
  Status = SendCmd(CMD0, CMD0_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "Cmd0 fails.\n"));
    return Status;
  }

  DEBUG ((EFI_D_INFO, "CMD0 response: %x\n", MmioRead32(MMCHS_RSP10)));

  //Send CMD5 command. 
  Status = SendCmd(CMD5, CMD5_INT_EN, CmdArgument);
  if (Status == EFI_SUCCESS) {
    DEBUG ((EFI_D_ERROR, "CMD5 Success. SDIO card. Follow SDIO card specification.\n"));
    DEBUG ((EFI_D_INFO, "CMD5 response: %x\n", MmioRead32(MMCHS_RSP10)));
    //NOTE: Returning unsupported error for now. Need to implement SDIO specification.
    return EFI_UNSUPPORTED; 
  } else {
    DEBUG ((EFI_D_INFO, "CMD5 fails. Not an SDIO card.\n"));
  }

  MmioOr32(MMCHS_SYSCTL, SRC);
  gBS->Stall(1000);
  while ((MmioRead32(MMCHS_SYSCTL) & SRC));

  //Send CMD8 command. (New v2.00 command for Voltage check)
  //Only 2.7V - 3.6V is supported for SD2.0, only SD 2.0 card can pass.
  //MMC & SD1.1 card will fail this command.
  CmdArgument = CMD8_ARG;
  Status = SendCmd(CMD8, CMD8_INT_EN, CmdArgument);
  if (Status == EFI_SUCCESS) {
    Response = MmioRead32(MMCHS_RSP10);
    DEBUG ((EFI_D_INFO, "CMD8 success. CMD8 response: %x\n", Response));
    if (Response != CmdArgument) {
      return EFI_DEVICE_ERROR;
    }
    DEBUG ((EFI_D_INFO, "Card is SD2.0\n"));
    SDCmd8Supported = TRUE; //Supports high capacity.
  } else {
    DEBUG ((EFI_D_INFO, "CMD8 fails. Not an SD2.0 card.\n"));
  }

  MmioOr32(MMCHS_SYSCTL, SRC);
  gBS->Stall(1000);
  while ((MmioRead32(MMCHS_SYSCTL) & SRC));

  //Poll till card is busy
  while (RetryCount < MAX_RETRY_COUNT) {
    //Send CMD55 command. 
    CmdArgument = 0;
    Status = SendCmd(CMD55, CMD55_INT_EN, CmdArgument);
    if (Status == EFI_SUCCESS) {
      DEBUG ((EFI_D_INFO, "CMD55 success. CMD55 response: %x\n", MmioRead32(MMCHS_RSP10)));
      gCardInfo->CardType = SD_CARD;
    } else {
      DEBUG ((EFI_D_INFO, "CMD55 fails.\n"));
      gCardInfo->CardType = MMC_CARD;
    }

    //Send appropriate command for the card type which got detected.
    if (gCardInfo->CardType == SD_CARD) {
      CmdArgument = ((UINTN *) &(gCardInfo->OCRData))[0];

      //Set HCS bit.
      if (SDCmd8Supported) {
        CmdArgument |= HCS;
      }

      Status = SendCmd(ACMD41, ACMD41_INT_EN, CmdArgument);
      if (EFI_ERROR(Status)) {
        DEBUG ((EFI_D_INFO, "ACMD41 fails.\n"));
        return Status;
      }
      ((UINT32 *) &(gCardInfo->OCRData))[0] = MmioRead32(MMCHS_RSP10);
      DEBUG ((EFI_D_INFO, "SD card detected. ACMD41 OCR: %x\n", ((UINT32 *) &(gCardInfo->OCRData))[0]));
    } else if (gCardInfo->CardType == MMC_CARD) {
      CmdArgument = 0;
      Status = SendCmd(CMD1, CMD1_INT_EN, CmdArgument);
      if (EFI_ERROR(Status)) {
        DEBUG ((EFI_D_INFO, "CMD1 fails.\n"));
        return Status;
      }
      Response = MmioRead32(MMCHS_RSP10);
      DEBUG ((EFI_D_INFO, "MMC card detected.. CMD1 response: %x\n", Response));

      //NOTE: For now, I am skipping this since I only have an SD card.
      //Compare card OCR and host OCR (Section 22.6.1.3.2.4)
      return EFI_UNSUPPORTED; //For now, MMC is not supported.
    }

    //Poll the card until it is out of its power-up sequence.
    if (gCardInfo->OCRData.Busy == 1) {

      if (SDCmd8Supported) {
        gCardInfo->CardType = SD_CARD_2;
      }

      //Card is ready. Check CCS (Card capacity status) bit (bit#30).
      //SD 2.0 standard card will response with CCS 0, SD high capacity card will respond with CCS 1.
      if (gCardInfo->OCRData.AccessMode & BIT1) {
        gCardInfo->CardType = SD_CARD_2_HIGH;
        DEBUG ((EFI_D_INFO, "High capacity card.\n"));
      } else {
        DEBUG ((EFI_D_INFO, "Standard capacity card.\n"));
      }

      break;
    }

    gBS->Stall(1000);
    RetryCount++;
  }

  if (RetryCount == MAX_RETRY_COUNT) {
    DEBUG ((EFI_D_ERROR, "Timeout error. RetryCount: %d\n", RetryCount));
    return EFI_TIMEOUT;
  }

  //Read CID data.
  CmdArgument = 0;
  Status = SendCmd(CMD2, CMD2_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "CMD2 fails. Status: %x\n", Status));
    return Status;
  }

  DEBUG ((EFI_D_INFO, "CMD2 response: %x %x %x %x\n", MmioRead32(MMCHS_RSP10), MmioRead32(MMCHS_RSP32), MmioRead32(MMCHS_RSP54), MmioRead32(MMCHS_RSP76)));

  //Parse CID register data.
  ParseCardCIDData(MmioRead32(MMCHS_RSP10), MmioRead32(MMCHS_RSP32), MmioRead32(MMCHS_RSP54), MmioRead32(MMCHS_RSP76));

  //Read RCA
  CmdArgument = 0;
  Status = SendCmd(CMD3, CMD3_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "CMD3 fails. Status: %x\n", Status));
    return Status;
  }

  //Set RCA for the detected card. RCA is CMD3 response.
  gCardInfo->RCA = (MmioRead32(MMCHS_RSP10) >> 16);
  DEBUG ((EFI_D_INFO, "CMD3 response: RCA %x\n", gCardInfo->RCA));

  //MMC Bus setting change after card identification.
  MmioAnd32(MMCHS_CON, ~OD);
  MmioOr32(MMCHS_HCTL, SDVS_3_0_V);
  UpdateMMCHSClkFrequency(CLKD_400KHZ); //Set the clock frequency to 400KHz.

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
GetCardSpecificData (
  VOID
  )
{
  EFI_STATUS Status;
  UINTN      CmdArgument;

  //Send CMD9 to retrieve CSD.
  CmdArgument = gCardInfo->RCA << 16;
  Status = SendCmd(CMD9, CMD9_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "CMD9 fails. Status: %x\n", Status));
    return Status;
  }

  //Populate 128-bit CSD register data.
  ((UINT32 *)&(gCardInfo->CSDData))[0] = MmioRead32(MMCHS_RSP10);
  ((UINT32 *)&(gCardInfo->CSDData))[1] = MmioRead32(MMCHS_RSP32);
  ((UINT32 *)&(gCardInfo->CSDData))[2] = MmioRead32(MMCHS_RSP54);
  ((UINT32 *)&(gCardInfo->CSDData))[3] = MmioRead32(MMCHS_RSP76);

  DEBUG ((EFI_D_INFO, "CMD9 response: %x %x %x %x\n", MmioRead32(MMCHS_RSP10), MmioRead32(MMCHS_RSP32), MmioRead32(MMCHS_RSP54), MmioRead32(MMCHS_RSP76)));

  //Calculate total number of blocks and max. data transfer rate supported by the detected card.
  GetCardConfigurationData();

  //Change MMCHS clock frequency to what detected card can support.
  UpdateMMCHSClkFrequency(gCardInfo->ClockFrequencySelect);

  return Status;
}

STATIC
EFI_STATUS
PerformCardConfiguration (
  VOID
  )
{
  UINTN      CmdArgument = 0;
  EFI_STATUS Status;

  //Send CMD7
  CmdArgument = gCardInfo->RCA << 16;
  Status = SendCmd(CMD7, CMD7_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "CMD7 fails. Status: %x\n", Status));
    return Status;
  }

  //Send CMD16 to set the block length
  CmdArgument = gCardInfo->BlockSize;
  Status = SendCmd(CMD16, CMD16_INT_EN, CmdArgument);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "CMD16 fails. Status: %x\n", Status));
    return Status;
  }

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
ReadBlockData(
  IN  EFI_BLOCK_IO_PROTOCOL       *This,
  OUT VOID                        *Buffer
  )
{
  UINTN MmcStatus;
  UINTN *DataBuffer = Buffer;
  UINTN DataSize = This->Media->BlockSize/4;
  UINTN Count;
  UINTN RetryCount = 0;

  //Check controller status to make sure there is no error.
  while (RetryCount < MAX_RETRY_COUNT) {
    do {
      //Read Status.
      MmcStatus = MmioRead32(MMCHS_STAT);
    } while(MmcStatus == 0);

    //Check if Buffer read ready (BRR) bit is set?
    if (MmcStatus & BRR) {

      //Clear BRR bit
      MmioOr32(MMCHS_STAT, BRR);

      //Read block worth of data.
      for (Count = 0; Count < DataSize; Count++) {
        *DataBuffer++ = MmioRead32(MMCHS_DATA);
      }
      break;
    }
    RetryCount++;
  }

  if (RetryCount == MAX_RETRY_COUNT) {
    return EFI_TIMEOUT;
  }

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
WriteBlockData(
  IN  EFI_BLOCK_IO_PROTOCOL       *This,
  OUT VOID                        *Buffer
  )
{
  UINTN MmcStatus;
  UINTN *DataBuffer = Buffer;
  UINTN DataSize = This->Media->BlockSize/4;
  UINTN Count;
  UINTN RetryCount = 0;

  //Check controller status to make sure there is no error.
  while (RetryCount < MAX_RETRY_COUNT) {
    do {
      //Read Status.
      MmcStatus = MmioRead32(MMCHS_STAT);
    } while(MmcStatus == 0);

    //Check if Buffer write ready (BWR) bit is set?
    if (MmcStatus & BWR) {

      //Clear BWR bit
      MmioOr32(MMCHS_STAT, BWR);

      //Write block worth of data.
      for (Count = 0; Count < DataSize; Count++) {
        MmioWrite32 (MMCHS_DATA, *DataBuffer++);
      }

      break;
    }
    RetryCount++;
  }

  if (RetryCount == MAX_RETRY_COUNT) {
    return EFI_TIMEOUT;
  }

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
TransferBlockData(
  IN  EFI_BLOCK_IO_PROTOCOL       *This,
  OUT VOID                        *Buffer,
  IN  OPERATION_TYPE              OperationType
  )
{
  EFI_STATUS Status;
  UINTN      MmcStatus;
  UINTN      RetryCount = 0;

  //Read or Write data.
  if (OperationType == READ) {
    Status = ReadBlockData(This, Buffer);
    if (EFI_ERROR(Status)) {
      DEBUG((EFI_D_ERROR, "ReadBlockData fails.\n"));
      return Status;
    }
  } else if (OperationType == WRITE) {
    Status = WriteBlockData(This, Buffer);
    if (EFI_ERROR(Status)) {
      DEBUG((EFI_D_ERROR, "WriteBlockData fails.\n"));
      return Status;
    }
  }

  //Check for the Transfer completion.
  while (RetryCount < MAX_RETRY_COUNT) {
    //Read Status
    do {
      MmcStatus = MmioRead32(MMCHS_STAT);
    } while (MmcStatus == 0);

    //Check if Transfer complete (TC) bit is set?
    if (MmcStatus & TC) {
      break;
    } else {
      DEBUG ((EFI_D_ERROR, "MmcStatus for TC: %x\n", MmcStatus));
      //Check if DEB, DCRC or DTO interrupt occured.
      if ((MmcStatus & DEB) | (MmcStatus & DCRC) | (MmcStatus & DTO)) {
        //There was an error during the data transfer.

        //Set SRD bit to 1 and wait until it return to 0x0.
        MmioOr32(MMCHS_SYSCTL, SRD);
        while((MmioRead32(MMCHS_SYSCTL) & SRD) != 0x0);

        return EFI_DEVICE_ERROR;
      }
    }
    RetryCount++;
  } 

  if (RetryCount == MAX_RETRY_COUNT) {
    DEBUG ((EFI_D_ERROR, "TransferBlockData timed out.\n"));
    return EFI_TIMEOUT;
  }

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
SdReadWrite (
  IN EFI_BLOCK_IO_PROTOCOL    *This,
  IN  UINTN                   Lba, 
  OUT VOID                    *Buffer, 
  IN  UINTN                   BufferSize,
  IN  OPERATION_TYPE          OperationType
  )
{
  EFI_STATUS Status;
  UINTN      RetryCount = 0;
  UINTN      NumBlocks;
  UINTN      Cmd = 0;
  UINTN      CmdInterruptEnable = 0;
  UINTN      CmdArgument = 0;

  //Check if the data lines are not in use.
  while ((RetryCount++ < MAX_RETRY_COUNT) && ((MmioRead32(MMCHS_PSTATE) & DATI_MASK) != DATI_ALLOWED));
  if (RetryCount == MAX_RETRY_COUNT) {
    return EFI_TIMEOUT;
  }

  //Populate the command information based on the operation type.
  if (OperationType == READ) {
    Cmd = CMD17; //Single block read
    CmdInterruptEnable = CMD17_INT_EN;
  } else if (OperationType == WRITE) {
    Cmd = CMD24; //Single block write
    CmdInterruptEnable = CMD24_INT_EN;
  }

  //Calculate total number of blocks its going to read.
  NumBlocks = (BufferSize + (This->Media->BlockSize - 1))/This->Media->BlockSize;

  //Set command argument based on the card access mode (Byte mode or Block mode)
  if (gCardInfo->OCRData.AccessMode & BIT1) {
    CmdArgument = (UINTN)Lba;
  } else {
    CmdArgument = (UINTN)Lba * This->Media->BlockSize;
  }

  while(NumBlocks) {
    //Send Command.
    Status = SendCmd(Cmd, CmdInterruptEnable, CmdArgument);
    if (EFI_ERROR(Status)) {
      DEBUG ((EFI_D_ERROR, "CMD fails. Status: %x\n", Status));
      return Status;
    }

    //Transfer a block worth of data.
    Status = TransferBlockData(This, Buffer, OperationType);
    if (EFI_ERROR(Status)) {
      DEBUG ((EFI_D_ERROR, "TransferBlockData fails. %x\n", Status));
      return Status;
    }

    //Adjust command argument.
    if (gCardInfo->OCRData.AccessMode & BIT1) {
      CmdArgument++; //Increase BlockIndex by one.
    } else {
      CmdArgument += This->Media->BlockSize; //Increase BlockIndex by BlockSize
    }

    //Adjust Buffer.
    Buffer = (UINT8 *)Buffer + This->Media->BlockSize;
    NumBlocks--;
  }

  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
MMCHSReset (
  IN EFI_BLOCK_IO_PROTOCOL          *This,
  IN BOOLEAN                        ExtendedVerification
  )
{
  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
MMCHSReadBlocks (
  IN EFI_BLOCK_IO_PROTOCOL          *This,
  IN UINT32                         MediaId,
  IN EFI_LBA                        Lba,
  IN UINTN                          BufferSize,
  OUT VOID                          *Buffer
  )
{
  EFI_STATUS Status;

  if (Buffer == NULL)
  {
    return EFI_INVALID_PARAMETER;
  }
  
  if (Lba > This->Media->LastBlock)
  {
    return EFI_INVALID_PARAMETER;
  }
  
  if ((BufferSize % This->Media->BlockSize) != 0)
  {
    return EFI_BAD_BUFFER_SIZE;
  }

  //Perform Read operation.
  Status = SdReadWrite(This, (UINTN)Lba, Buffer, BufferSize, READ);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "Read operation fails.\n"));
  }

  return Status;
}

EFI_STATUS
EFIAPI
MMCHSWriteBlocks (
  IN EFI_BLOCK_IO_PROTOCOL          *This,
  IN UINT32                         MediaId,
  IN EFI_LBA                        Lba,
  IN UINTN                          BufferSize,
  IN VOID                           *Buffer
  )
{
  EFI_STATUS Status;

  if (Buffer == NULL) {
    return EFI_INVALID_PARAMETER;
  }
  
  if (Lba > This->Media->LastBlock) {
    return EFI_INVALID_PARAMETER;
  }
  
  if ((BufferSize % This->Media->BlockSize) != 0) {
    return EFI_BAD_BUFFER_SIZE;
  }

  if (This->Media->ReadOnly) {
    return EFI_WRITE_PROTECTED;
  }

  //Perform write operation.
  Status = SdReadWrite(This, (UINTN)Lba, Buffer, BufferSize, WRITE);
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "Write operation fails.\n"));
  }

  return Status;
}

EFI_STATUS
EFIAPI
MMCHSFlushBlocks (
  IN EFI_BLOCK_IO_PROTOCOL  *This
  )
{
  return EFI_SUCCESS;
}

EFI_BLOCK_IO_PROTOCOL BlockIo = 
{
  EFI_BLOCK_IO_INTERFACE_REVISION,   // Revision
  &MMCHSMedia,                       // *Media
  MMCHSReset,                        // Reset
  MMCHSReadBlocks,                   // ReadBlocks
  MMCHSWriteBlocks,                  // WriteBlocks
  MMCHSFlushBlocks                   // FlushBlocks
};

EFI_STATUS
MMCHSInitialize (
  IN EFI_HANDLE         ImageHandle,
  IN EFI_SYSTEM_TABLE   *SystemTable
  )
{
  EFI_STATUS  Status;

  Status = gBS->LocateProtocol(&gEmbeddedExternalDeviceProtocolGuid, NULL, (VOID **)&gTPS65950);
  ASSERT_EFI_ERROR(Status);

  gCardInfo = (CARD_INFO *)AllocateZeroPool(sizeof(CARD_INFO));
  if (gCardInfo == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
	
  //Initialize MMC host controller.
  Status = InitializeMMCHS();
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "Initialize MMC host controller fails. Status: %x\n", Status));
    return Status;
  }
  
  //Card idenfication
  Status = PerformCardIdenfication();
  if (EFI_ERROR(Status)) {
    DEBUG ((EFI_D_ERROR, "No MMC/SD card detected.\n"));
    return EFI_SUCCESS; //NOTE: Check if this is correct..
  }
  
  //Get CSD (Card specific data) for the detected card.
  Status = GetCardSpecificData();
  if (EFI_ERROR(Status)) {
    return Status;
  }
  
  //Configure the card in data transfer mode.
  Status = PerformCardConfiguration();
  if (EFI_ERROR(Status)) {
    return Status;
  }

  //Patch the Media structure.
  MMCHSMedia.LastBlock = (gCardInfo->NumBlocks - 1);
  MMCHSMedia.BlockSize = gCardInfo->BlockSize;

  //Publish BlockIO.
  Status = gBS->InstallMultipleProtocolInterfaces(&ImageHandle, 
                                                  &gEfiBlockIoProtocolGuid, &BlockIo, 
                                                  &gEfiDevicePathProtocolGuid, &gMmcHsDevicePath,
                                                  NULL);
  return Status;
}