audk/IntelFrameworkModulePkg/Csm/LegacyBiosDxe/LegacyCmos.c

/** @file
  This code fills in standard CMOS values and updates the standard CMOS
  checksum. The Legacy16 code or LegacyBiosPlatform.c is responsible for
  non-standard CMOS locations and non-standard checksums.

Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>

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 "LegacyBiosInterface.h"

/**
  Read CMOS register through index/data port.

  @param[in]  Index   The index of the CMOS register to read.

  @return  The data value from the CMOS register specified by Index.

**/
UINT8
LegacyReadStandardCmos (
  IN UINT8  Index
  )
{
  IoWrite8 (PORT_70, Index);
  return IoRead8 (PORT_71);
}

/**
  Write CMOS register through index/data port.

  @param[in]  Index  The index of the CMOS register to write.
  @param[in]  Value  The value of CMOS register to write.

  @return  The value written to the CMOS register specified by Index.

**/
UINT8
LegacyWriteStandardCmos (
  IN UINT8  Index,
  IN UINT8  Value
  )
{
  IoWrite8 (PORT_70, Index);
  return IoWrite8 (PORT_71, Value);
}

/**
  Calculate the new standard CMOS checksum and write it.

  @param  Private      Legacy BIOS Instance data

  @retval EFI_SUCCESS  Calculate 16-bit checksum successfully

**/
EFI_STATUS
LegacyCalculateWriteStandardCmosChecksum (
  VOID
  )
{
  UINT8   Register;
  UINT16  Checksum;

  for (Checksum = 0, Register = 0x10; Register < 0x2e; Register++) {
    Checksum = (UINT16)(Checksum + LegacyReadStandardCmos (Register));
  }
  LegacyWriteStandardCmos (CMOS_2E, (UINT8)(Checksum >> 8));
  LegacyWriteStandardCmos (CMOS_2F, (UINT8)(Checksum & 0xff));
  return EFI_SUCCESS;
}


/**
  Fill in the standard CMOS stuff before Legacy16 load

  @param  Private      Legacy BIOS Instance data

  @retval EFI_SUCCESS  It should always work.

**/
EFI_STATUS
LegacyBiosInitCmos (
  IN  LEGACY_BIOS_INSTANCE    *Private
  )
{
  UINT32  Size;

  //
  //  Clear all errors except RTC lost power
  //
  LegacyWriteStandardCmos (CMOS_0E, (UINT8)(LegacyReadStandardCmos (CMOS_0E) & BIT7));

  //
  // Update CMOS locations 15,16,17,18,30,31 and 32
  // CMOS 16,15 = 640Kb = 0x280
  // CMOS 18,17 = 31,30 = 15Mb max in 1Kb increments =0x3C00 max
  // CMOS 32 = 0x20
  //
  LegacyWriteStandardCmos (CMOS_15, 0x80);
  LegacyWriteStandardCmos (CMOS_16, 0x02);

  Size = 15 * SIZE_1MB;
  if (Private->IntThunk->EfiToLegacy16InitTable.OsMemoryAbove1Mb < (15 * SIZE_1MB)) {
    Size  = Private->IntThunk->EfiToLegacy16InitTable.OsMemoryAbove1Mb >> 10;
  }

  LegacyWriteStandardCmos (CMOS_17, (UINT8)(Size & 0xFF));
  LegacyWriteStandardCmos (CMOS_30, (UINT8)(Size & 0xFF));
  LegacyWriteStandardCmos (CMOS_18, (UINT8)(Size >> 8));
  LegacyWriteStandardCmos (CMOS_31, (UINT8)(Size >> 8));

  LegacyCalculateWriteStandardCmosChecksum ();

  return EFI_SUCCESS;
}