MdeModulePkg/Bus/Pci/PciBusDxe/PciPowerManagement.c

   1 /** @file
   2   Power management support functions implementation for PCI Bus module.
   3
   4 Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
   5 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "PciBus.h"
  10
  11 /**
  12   This function is intended to turn off PWE assertion and
  13   put the device to D0 state if the device supports
  14   PCI Power Management.
  15
  16   @param PciIoDevice      PCI device instance.
  17
  18   @retval EFI_UNSUPPORTED PCI Device does not support power management.
  19   @retval EFI_SUCCESS     Turned off PWE successfully.
  20
  21 **/
  22 EFI_STATUS
  23 ResetPowerManagementFeature (
  24   IN PCI_IO_DEVICE  *PciIoDevice
  25   )
  26 {
  27   EFI_STATUS  Status;
  28   UINT8       PowerManagementRegBlock;
  29   UINT16      PowerManagementCSR;
  30
  31   PowerManagementRegBlock = 0;
  32
  33   Status = LocateCapabilityRegBlock (
  34              PciIoDevice,
  35              EFI_PCI_CAPABILITY_ID_PMI,
  36              &PowerManagementRegBlock,
  37              NULL
  38              );
  39
  40   if (EFI_ERROR (Status)) {
  41     return EFI_UNSUPPORTED;
  42   }
  43
  44   //
  45   // Turn off the PWE assertion and put the device into D0 State
  46   //
  47
  48   //
  49   // Read PMCSR
  50   //
  51   Status = PciIoDevice->PciIo.Pci.Read (
  52                                     &PciIoDevice->PciIo,
  53                                     EfiPciIoWidthUint16,
  54                                     PowerManagementRegBlock + 4,
  55                                     1,
  56                                     &PowerManagementCSR
  57                                     );
  58
  59   if (!EFI_ERROR (Status)) {
  60     //
  61     // Clear PME_Status bit
  62     //
  63     PowerManagementCSR |= BIT15;
  64     //
  65     // Clear PME_En bit. PowerState = D0.
  66     //
  67     PowerManagementCSR &= ~(BIT8 | BIT1 | BIT0);
  68
  69     //
  70     // Write PMCSR
  71     //
  72     Status = PciIoDevice->PciIo.Pci.Write (
  73                                       &PciIoDevice->PciIo,
  74                                       EfiPciIoWidthUint16,
  75                                       PowerManagementRegBlock + 4,
  76                                       1,
  77                                       &PowerManagementCSR
  78                                       );
  79   }
  80
  81   return Status;
  82 }