Revert "ArmVirtPkg/FdtClientDxe: make DT table installation !ACPI dependent"

This reverts commit 78c41ff519.

We realized that DXE drivers that are independent of AcpiPlatformDxe (that
is, independent of QEMU's ACPI generation), such as RamDiskDxe and
BootGraphicsResourceTableDxe, may produce and/or manipulate ACPI tables,
at driver dispatch or even at Ready To Boot.

This makes it unsafe for us to check for ACPI presence in the UEFI system
config table in a Ready To Boot callback, in order to decide about
exposing the DT.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

ArmVirtPkg/ArmVirtPkg.dec

@@ -58,3 +58,13 @@
   # EFI_VT_100_GUID.
   #
   gArmVirtTokenSpaceGuid.PcdTerminalTypeGuidBuffer|{0x65, 0x60, 0xA6, 0xDF, 0x19, 0xB4, 0xD3, 0x11, 0x9A, 0x2D, 0x00, 0x90, 0x27, 0x3F, 0xC1, 0x4D}|VOID*|0x00000007
+
+[PcdsFeatureFlag]
+  #
+  # Pure ACPI boot
+  #
+  # Inhibit installation of the FDT as a configuration table if this feature
+  # PCD is TRUE. Otherwise, the OS is presented with both a DT and an ACPI
+  # description of the platform, and it is up to the OS to choose.
+  #
+  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot|FALSE|BOOLEAN|0x0000000a

ArmVirtPkg/ArmVirtQemu.dsc

@@ -34,6 +34,7 @@
   # -D FLAG=VALUE
   #
   DEFINE SECURE_BOOT_ENABLE      = FALSE
+  DEFINE PURE_ACPI_BOOT_ENABLE   = FALSE
 
 !include ArmVirtPkg/ArmVirt.dsc.inc
 
@@ -94,6 +95,10 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
+!if $(PURE_ACPI_BOOT_ENABLE) == TRUE
+  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot|TRUE
+!endif
+
 [PcdsFixedAtBuild.common]
   gArmPlatformTokenSpaceGuid.PcdCoreCount|1
 !if $(ARCH) == AARCH64

ArmVirtPkg/FdtClientDxe/FdtClientDxe.c

@@ -17,11 +17,9 @@
 #include <Library/DebugLib.h>
 #include <Library/UefiDriverEntryPoint.h>
 #include <Library/UefiBootServicesTableLib.h>
-#include <Library/UefiLib.h>
 #include <Library/HobLib.h>
 #include <libfdt.h>
 
-#include <Guid/Acpi.h>
 #include <Guid/EventGroup.h>
 #include <Guid/Fdt.h>
 #include <Guid/FdtHob.h>
@@ -318,16 +316,12 @@ OnReadyToBoot (
   )
 {
   EFI_STATUS      Status;
-  VOID            *Table;
 
+  if (!FeaturePcdGet (PcdPureAcpiBoot)) {
     //
-  // Only install the FDT as a configuration table if we are not exposing
-  // ACPI 2.0 (or later) tables. Note that the legacy ACPI table GUID has
-  // no meaning on ARM since we need at least ACPI 5.0 support, and the
-  // 64-bit ACPI 2.0 table GUID is mandatory in that case.
+    // Only install the FDT as a configuration table if we want to leave it up
+    // to the OS to decide whether it prefers ACPI over DT.
     //
-  Status = EfiGetSystemConfigurationTable (&gEfiAcpi20TableGuid, &Table);
-  if (EFI_ERROR (Status) || Table == NULL) {
     Status = gBS->InstallConfigurationTable (&gFdtTableGuid, mDeviceTreeBase);
     ASSERT_EFI_ERROR (Status);
   }

ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf

@@ -37,16 +37,17 @@
   HobLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
-  UefiLib
 
 [Protocols]
   gFdtClientProtocolGuid                  ## PRODUCES
 
 [Guids]
-  gEfiAcpi20TableGuid
   gEfiEventReadyToBootGuid
   gFdtHobGuid
   gFdtTableGuid
 
+[FeaturePcd]
+  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot
+
 [Depex]
   TRUE