ResetAudioTrafficClass.c

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#include <Uefi.h>
 
#include <IndustryStandard/Pci.h>
 
#include <Protocol/PciIo.h>
 
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/IoLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/OcDeviceMiscLib.h>
 
#include "PciExtInternal.h"
 
VOID
ResetAudioTrafficClass (
  VOID
  )
{
  EFI_STATUS           Status;
  UINTN                HandleCount;
  EFI_HANDLE           *HandleBuffer;
  UINTN                Index;
  EFI_PCI_IO_PROTOCOL  *PciIo;
  PCI_CLASSCODE        ClassCode;
  UINT8                TrafficClass;
 
  Status = gBS->LocateHandleBuffer (
                  ByProtocol,
                  &gEfiPciIoProtocolGuid,
                  NULL,
                  &HandleCount,
                  &HandleBuffer
                  );
 
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_INFO, "OCDM: No PCI devices for TCSEL reset - %r\n", Status));
    return;
  }
 
  for (Index = 0; Index < HandleCount; ++Index) {
    Status = gBS->HandleProtocol (
                    HandleBuffer[Index],
                    &gEfiPciIoProtocolGuid,
                    (VOID **)&PciIo
                    );
 
    if (EFI_ERROR (Status)) {
      continue;
    }
 
    Status = PciIo->Pci.Read (
                          PciIo,
                          EfiPciIoWidthUint8,
                          PCI_CLASSCODE_OFFSET,
                          sizeof (PCI_CLASSCODE) / sizeof (UINT8),
                          &ClassCode
                          );
    if (EFI_ERROR (Status)) {
      continue;
    }
 
    if ((ClassCode.BaseCode == PCI_CLASS_MEDIA) &&
        ((ClassCode.SubClassCode == PCI_CLASS_MEDIA_AUDIO) ||
         (ClassCode.SubClassCode == PCI_CLASS_MEDIA_HDA)))
    {
      Status = PciIo->Pci.Read (PciIo, EfiPciIoWidthUint8, PCI_MEDIA_TCSEL_OFFSET, 1, &TrafficClass);
      if (EFI_ERROR (Status)) {
        continue;
      }
 
      DEBUG ((
        DEBUG_INFO,
        "OCDM: Discovered audio device at %u/%u with TCSEL %X\n",
        (UINT32)(Index + 1),
        (UINT32)HandleCount,
        TrafficClass
        ));
 
      //
      // Update Traffic Class Select Register to TC0.
      // This is required for AppleHDA to output audio on some machines.
      // See Intel I/O Controller Hub 9 (ICH9) Family Datasheet for more details.
      //
      if ((TrafficClass & TCSEL_CLASS_MASK) != 0) {
        TrafficClass &= ~TCSEL_CLASS_MASK;
        PciIo->Pci.Write (PciIo, EfiPciIoWidthUint8, PCI_MEDIA_TCSEL_OFFSET, 1, &TrafficClass);
      }
    }
  }
}