PciDecoding.c

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#include <Library/AcpiPlatformLib.h>
#include <Library/DebugLib.h>                  // DEBUG()
#include <Library/MemoryAllocationLib.h>       // AllocatePool()
#include <Library/UefiBootServicesTableLib.h>  // gBS
 
VOID
EnablePciDecoding (
  OUT ORIGINAL_ATTRIBUTES  **OriginalAttributes,
  OUT UINTN                *Count
  )
{
  EFI_STATUS           Status;
  UINTN                NoHandles;
  EFI_HANDLE           *Handles;
  ORIGINAL_ATTRIBUTES  *OrigAttrs;
  UINTN                Idx;
 
  *OriginalAttributes = NULL;
  *Count              = 0;
 
  if (PcdGetBool (PcdPciDisableBusEnumeration)) {
    //
    // The platform downloads ACPI tables from QEMU in general, but there are
    // no root bridges in this execution. We're done.
    //
    return;
  }
 
  Status = gBS->LocateHandleBuffer (
                  ByProtocol,
                  &gEfiPciIoProtocolGuid,
                  NULL /* SearchKey */,
                  &NoHandles,
                  &Handles
                  );
  if (Status == EFI_NOT_FOUND) {
    //
    // No PCI devices were found on either of the root bridges. We're done.
    //
    return;
  }
 
  if (EFI_ERROR (Status)) {
    DEBUG ((
      DEBUG_WARN,
      "%a: LocateHandleBuffer(): %r\n",
      __func__,
      Status
      ));
    return;
  }
 
  OrigAttrs = AllocatePool (NoHandles * sizeof *OrigAttrs);
  if (OrigAttrs == NULL) {
    DEBUG ((
      DEBUG_WARN,
      "%a: AllocatePool(): out of resources\n",
      __func__
      ));
    goto FreeHandles;
  }
 
  for (Idx = 0; Idx < NoHandles; ++Idx) {
    EFI_PCI_IO_PROTOCOL  *PciIo;
    UINT64               Attributes;
 
    //
    // Look up PciIo on the handle and stash it
    //
    Status = gBS->HandleProtocol (
                    Handles[Idx],
                    &gEfiPciIoProtocolGuid,
                    (VOID **)&PciIo
                    );
    ASSERT_EFI_ERROR (Status);
    OrigAttrs[Idx].PciIo = PciIo;
 
    //
    // Stash the current attributes
    //
    Status = PciIo->Attributes (
                      PciIo,
                      EfiPciIoAttributeOperationGet,
                      0,
                      &OrigAttrs[Idx].PciAttributes
                      );
    if (EFI_ERROR (Status)) {
      DEBUG ((
        DEBUG_WARN,
        "%a: EfiPciIoAttributeOperationGet: %r\n",
        __func__,
        Status
        ));
      goto RestoreAttributes;
    }
 
    //
    // Retrieve supported attributes
    //
    Status = PciIo->Attributes (
                      PciIo,
                      EfiPciIoAttributeOperationSupported,
                      0,
                      &Attributes
                      );
    if (EFI_ERROR (Status)) {
      DEBUG ((
        DEBUG_WARN,
        "%a: EfiPciIoAttributeOperationSupported: %r\n",
        __func__,
        Status
        ));
      goto RestoreAttributes;
    }
 
    //
    // Enable IO and MMIO decoding
    //
    Attributes &= EFI_PCI_IO_ATTRIBUTE_IO | EFI_PCI_IO_ATTRIBUTE_MEMORY;
    Status      = PciIo->Attributes (
                           PciIo,
                           EfiPciIoAttributeOperationEnable,
                           Attributes,
                           NULL
                           );
    if (EFI_ERROR (Status)) {
      DEBUG ((
        DEBUG_WARN,
        "%a: EfiPciIoAttributeOperationEnable: %r\n",
        __func__,
        Status
        ));
      goto RestoreAttributes;
    }
  }
 
  //
  // Success
  //
  FreePool (Handles);
  *OriginalAttributes = OrigAttrs;
  *Count              = NoHandles;
  return;
 
RestoreAttributes:
  while (Idx > 0) {
    --Idx;
    OrigAttrs[Idx].PciIo->Attributes (
                            OrigAttrs[Idx].PciIo,
                            EfiPciIoAttributeOperationSet,
                            OrigAttrs[Idx].PciAttributes,
                            NULL
                            );
  }
 
  FreePool (OrigAttrs);
 
FreeHandles:
  FreePool (Handles);
}
 
VOID
RestorePciDecoding (
  IN ORIGINAL_ATTRIBUTES  *OriginalAttributes,
  IN UINTN                Count
  )
{
  UINTN  Idx;
 
  ASSERT ((OriginalAttributes == NULL) == (Count == 0));
  if (OriginalAttributes == NULL) {
    return;
  }
 
  for (Idx = 0; Idx < Count; ++Idx) {
    OriginalAttributes[Idx].PciIo->Attributes (
                                     OriginalAttributes[Idx].PciIo,
                                     EfiPciIoAttributeOperationSet,
                                     OriginalAttributes[Idx].PciAttributes,
                                     NULL
                                     );
  }
 
  FreePool (OriginalAttributes);
}