1 files changed, 117 insertions, 0 deletions
diff --git a/OvmfPkg/Csm/LegacyBiosDxe/LegacyCmos.c b/OvmfPkg/Csm/LegacyBiosDxe/LegacyCmos.c
new file mode 100644
index 0000000000..de25e06184
--- /dev/null
+++ b/OvmfPkg/Csm/LegacyBiosDxe/LegacyCmos.c
@@ -0,0 +1,117 @@
+/** @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>
+
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#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;
+}