OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c

   1 /** @file
   2
   3   Stateful and implicitly initialized fw_cfg library implementation.
   4
   5   Copyright (C) 2013, Red Hat, Inc.
   6   Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
   7
   8   This program and the accompanying materials are licensed and made available
   9   under the terms and conditions of the BSD License which accompanies this
  10   distribution.  The full text of the license may be found at
  11   http://opensource.org/licenses/bsd-license.php
  12
  13   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  14   WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  15 **/
  16
  17 #include <Library/DebugLib.h>
  18 #include <Library/QemuFwCfgLib.h>
  19
  20 #include "QemuFwCfgLibInternal.h"
  21
  22 STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
  23 STATIC BOOLEAN mQemuFwCfgDmaSupported;
  24
  25
  26 /**
  27   Returns a boolean indicating if the firmware configuration interface
  28   is available or not.
  29
  30   This function may change fw_cfg state.
  31
  32   @retval    TRUE   The interface is available
  33   @retval    FALSE  The interface is not available
  34
  35 **/
  36 BOOLEAN
  37 EFIAPI
  38 QemuFwCfgIsAvailable (
  39   VOID
  40   )
  41 {
  42   return InternalQemuFwCfgIsAvailable ();
  43 }
  44
  45
  46 RETURN_STATUS
  47 EFIAPI
  48 QemuFwCfgInitialize (
  49   VOID
  50   )
  51 {
  52   UINT32 Signature;
  53   UINT32 Revision;
  54
  55   //
  56   // Enable the access routines while probing to see if it is supported.
  57   // For probing we always use the IO Port (IoReadFifo8()) access method.
  58   //
  59   mQemuFwCfgSupported = TRUE;
  60   mQemuFwCfgDmaSupported = FALSE;
  61
  62   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  63   Signature = QemuFwCfgRead32 ();
  64   DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  65   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  66   Revision = QemuFwCfgRead32 ();
  67   DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  68   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  69       (Revision < 1)
  70      ) {
  71     DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
  72     mQemuFwCfgSupported = FALSE;
  73     return RETURN_SUCCESS;
  74   }
  75
  76   if ((Revision & FW_CFG_F_DMA) == 0) {
  77     DEBUG ((DEBUG_INFO, "QemuFwCfg interface (IO Port) is supported.\n"));
  78   } else {
  79     mQemuFwCfgDmaSupported = TRUE;
  80     DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
  81   }
  82   return RETURN_SUCCESS;
  83 }
  84
  85
  86 /**
  87   Returns a boolean indicating if the firmware configuration interface is
  88   available for library-internal purposes.
  89
  90   This function never changes fw_cfg state.
  91
  92   @retval    TRUE   The interface is available internally.
  93   @retval    FALSE  The interface is not available internally.
  94 **/
  95 BOOLEAN
  96 InternalQemuFwCfgIsAvailable (
  97   VOID
  98   )
  99 {
 100   return mQemuFwCfgSupported;
 101 }
 102
 103 /**
 104   Returns a boolean indicating whether QEMU provides the DMA-like access method
 105   for fw_cfg.
 106
 107   @retval    TRUE   The DMA-like access method is available.
 108   @retval    FALSE  The DMA-like access method is unavailable.
 109 **/
 110 BOOLEAN
 111 InternalQemuFwCfgDmaIsAvailable (
 112   VOID
 113   )
 114 {
 115   return mQemuFwCfgDmaSupported;
 116 }