OvmfPkg/Csm/LegacyBiosDxe/LegacyCmos.c

   1 /** @file
   2   This code fills in standard CMOS values and updates the standard CMOS
   3   checksum. The Legacy16 code or LegacyBiosPlatform.c is responsible for
   4   non-standard CMOS locations and non-standard checksums.
   5
   6 Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
   7
   8 SPDX-License-Identifier: BSD-2-Clause-Patent
   9
  10 **/
  11
  12 #include "LegacyBiosInterface.h"
  13
  14 /**
  15   Read CMOS register through index/data port.
  16
  17   @param[in]  Index   The index of the CMOS register to read.
  18
  19   @return  The data value from the CMOS register specified by Index.
  20
  21 **/
  22 UINT8
  23 LegacyReadStandardCmos (
  24   IN UINT8  Index
  25   )
  26 {
  27   IoWrite8 (PORT_70, Index);
  28   return IoRead8 (PORT_71);
  29 }
  30
  31 /**
  32   Write CMOS register through index/data port.
  33
  34   @param[in]  Index  The index of the CMOS register to write.
  35   @param[in]  Value  The value of CMOS register to write.
  36
  37   @return  The value written to the CMOS register specified by Index.
  38
  39 **/
  40 UINT8
  41 LegacyWriteStandardCmos (
  42   IN UINT8  Index,
  43   IN UINT8  Value
  44   )
  45 {
  46   IoWrite8 (PORT_70, Index);
  47   return IoWrite8 (PORT_71, Value);
  48 }
  49
  50 /**
  51   Calculate the new standard CMOS checksum and write it.
  52
  53   @param  Private      Legacy BIOS Instance data
  54
  55   @retval EFI_SUCCESS  Calculate 16-bit checksum successfully
  56
  57 **/
  58 EFI_STATUS
  59 LegacyCalculateWriteStandardCmosChecksum (
  60   VOID
  61   )
  62 {
  63   UINT8   Register;
  64   UINT16  Checksum;
  65
  66   for (Checksum = 0, Register = 0x10; Register < 0x2e; Register++) {
  67     Checksum = (UINT16)(Checksum + LegacyReadStandardCmos (Register));
  68   }
  69   LegacyWriteStandardCmos (CMOS_2E, (UINT8)(Checksum >> 8));
  70   LegacyWriteStandardCmos (CMOS_2F, (UINT8)(Checksum & 0xff));
  71   return EFI_SUCCESS;
  72 }
  73
  74
  75 /**
  76   Fill in the standard CMOS stuff before Legacy16 load
  77
  78   @param  Private      Legacy BIOS Instance data
  79
  80   @retval EFI_SUCCESS  It should always work.
  81
  82 **/
  83 EFI_STATUS
  84 LegacyBiosInitCmos (
  85   IN  LEGACY_BIOS_INSTANCE    *Private
  86   )
  87 {
  88   UINT32  Size;
  89
  90   //
  91   //  Clear all errors except RTC lost power
  92   //
  93   LegacyWriteStandardCmos (CMOS_0E, (UINT8)(LegacyReadStandardCmos (CMOS_0E) & BIT7));
  94
  95   //
  96   // Update CMOS locations 15,16,17,18,30,31 and 32
  97   // CMOS 16,15 = 640Kb = 0x280
  98   // CMOS 18,17 = 31,30 = 15Mb max in 1Kb increments =0x3C00 max
  99   // CMOS 32 = 0x20
 100   //
 101   LegacyWriteStandardCmos (CMOS_15, 0x80);
 102   LegacyWriteStandardCmos (CMOS_16, 0x02);
 103
 104   Size = 15 * SIZE_1MB;
 105   if (Private->IntThunk->EfiToLegacy16InitTable.OsMemoryAbove1Mb < (15 * SIZE_1MB)) {
 106     Size  = Private->IntThunk->EfiToLegacy16InitTable.OsMemoryAbove1Mb >> 10;
 107   }
 108
 109   LegacyWriteStandardCmos (CMOS_17, (UINT8)(Size & 0xFF));
 110   LegacyWriteStandardCmos (CMOS_30, (UINT8)(Size & 0xFF));
 111   LegacyWriteStandardCmos (CMOS_18, (UINT8)(Size >> 8));
 112   LegacyWriteStandardCmos (CMOS_31, (UINT8)(Size >> 8));
 113
 114   LegacyCalculateWriteStandardCmosChecksum ();
 115
 116   return EFI_SUCCESS;
 117 }