OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c

   1 /** @file
   2   Provide constructor and GetTick for Dxe instance of ACPI Timer Library
   3
   4   Copyright (C) 2014, Gabriel L. Somlo <somlo@cmu.edu>
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7 **/
   8
   9 #include <Library/DebugLib.h>
  10 #include <Library/IoLib.h>
  11 #include <Library/PcdLib.h>
  12 #include <Library/PciLib.h>
  13 #include <OvmfPlatforms.h>
  14
  15 //
  16 // Cached ACPI Timer IO Address
  17 //
  18 STATIC UINT32  mAcpiTimerIoAddr;
  19
  20 /**
  21   The constructor function caches the ACPI tick counter address
  22
  23   At the time this constructor runs (DXE_CORE or later), ACPI IO space
  24   has already been enabled by either PlatformPei or by the "Base"
  25   instance of this library.
  26   In order to avoid querying the underlying platform type during each
  27   tick counter read operation, we cache the counter address during
  28   initialization of this instance of the Timer Library.
  29
  30   @retval EFI_SUCCESS   The constructor always returns RETURN_SUCCESS.
  31
  32 **/
  33 RETURN_STATUS
  34 EFIAPI
  35 AcpiTimerLibConstructor (
  36   VOID
  37   )
  38 {
  39   UINT16  HostBridgeDevId;
  40   UINTN   Pmba;
  41
  42   //
  43   // Query Host Bridge DID to determine platform type
  44   //
  45   HostBridgeDevId = PcdGet16 (PcdOvmfHostBridgePciDevId);
  46   switch (HostBridgeDevId) {
  47     case INTEL_82441_DEVICE_ID:
  48       Pmba = POWER_MGMT_REGISTER_PIIX4 (PIIX4_PMBA);
  49       break;
  50     case INTEL_Q35_MCH_DEVICE_ID:
  51       Pmba = POWER_MGMT_REGISTER_Q35 (ICH9_PMBASE);
  52       break;
  53     default:
  54       DEBUG ((
  55         DEBUG_ERROR,
  56         "%a: Unknown Host Bridge Device ID: 0x%04x\n",
  57         __FUNCTION__,
  58         HostBridgeDevId
  59         ));
  60       ASSERT (FALSE);
  61       return RETURN_UNSUPPORTED;
  62   }
  63
  64   mAcpiTimerIoAddr = (PciRead32 (Pmba) & ~PMBA_RTE) + ACPI_TIMER_OFFSET;
  65
  66   return RETURN_SUCCESS;
  67 }
  68
  69 /**
  70   Internal function to read the current tick counter of ACPI.
  71
  72   Read the current ACPI tick counter using the counter address cached
  73   by this instance's constructor.
  74
  75   @return The tick counter read.
  76
  77 **/
  78 UINT32
  79 InternalAcpiGetTimerTick (
  80   VOID
  81   )
  82 {
  83   //
  84   //   Return the current ACPI timer value.
  85   //
  86   return IoRead32 (mAcpiTimerIoAddr);
  87 }