[PATCH v2 4/4] ArmVirtPkg/FdtClientDxe: make DT table installation !ACPI dependent

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Instead of having a build time switch to prevent the FDT configuration
table from being installed, make this behavior dependent on whether we
are passing ACPI tables to the OS. This is done by looking for the
ACPI 2.0 configuration table, and only installing the FDT one if the
ACPI one cannot be found.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmVirtPkg/ArmVirtPkg.dec                | 10 ----------
 ArmVirtPkg/ArmVirtQemu.dsc               |  5 -----
 ArmVirtPkg/FdtClientDxe/FdtClientDxe.c   | 16 +++++++++++-----
 ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf |  5 ++---
 4 files changed, 13 insertions(+), 23 deletions(-)

diff --git a/ArmVirtPkg/ArmVirtPkg.dec b/ArmVirtPkg/ArmVirtPkg.dec
index a5ec42166445..efe83a383d55 100644
--- a/ArmVirtPkg/ArmVirtPkg.dec
+++ b/ArmVirtPkg/ArmVirtPkg.dec
@@ -58,13 +58,3 @@ [PcdsFixedAtBuild, PcdsPatchableInModule]
   # 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
diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 477dfdcfc764..7b266b98b949 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -34,7 +34,6 @@ [Defines]
   # -D FLAG=VALUE
   #
   DEFINE SECURE_BOOT_ENABLE      = FALSE
-  DEFINE PURE_ACPI_BOOT_ENABLE   = FALSE
 
 !include ArmVirtPkg/ArmVirt.dsc.inc
 
@@ -94,10 +93,6 @@ [PcdsFeatureFlag.common]
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
-!if $(PURE_ACPI_BOOT_ENABLE) == TRUE
-  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot|TRUE
-!endif
-
 [PcdsFixedAtBuild.common]
   gArmPlatformTokenSpaceGuid.PcdCoreCount|1
 !if $(ARCH) == AARCH64
diff --git a/ArmVirtPkg/FdtClientDxe/FdtClientDxe.c b/ArmVirtPkg/FdtClientDxe/FdtClientDxe.c
index 4cf79f70cb2a..21c1074e331c 100644
--- a/ArmVirtPkg/FdtClientDxe/FdtClientDxe.c
+++ b/ArmVirtPkg/FdtClientDxe/FdtClientDxe.c
@@ -17,9 +17,11 @@
 #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>
@@ -316,12 +318,16 @@ OnReadyToBoot (
   )
 {
   EFI_STATUS      Status;
+  VOID            *Table;
 
-  if (!FeaturePcdGet (PcdPureAcpiBoot)) {
-    //
-    // 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.
-    //
+  //
+  // 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.
+  //
+  Status = EfiGetSystemConfigurationTable (&gEfiAcpi20TableGuid, &Table);
+  if (EFI_ERROR (Status) || Table == NULL) {
     Status = gBS->InstallConfigurationTable (&gFdtTableGuid, mDeviceTreeBase);
     ASSERT_EFI_ERROR (Status);
   }
diff --git a/ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf b/ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf
index 00017727c32c..9861f41e968b 100644
--- a/ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf
+++ b/ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf
@@ -37,17 +37,16 @@ [LibraryClasses]
   HobLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
+  UefiLib
 
 [Protocols]
   gFdtClientProtocolGuid                  ## PRODUCES
 
 [Guids]
+  gEfiAcpi20TableGuid
   gEfiEventReadyToBootGuid
   gFdtHobGuid
   gFdtTableGuid
 
-[FeaturePcd]
-  gArmVirtTokenSpaceGuid.PcdPureAcpiBoot
-
 [Depex]
   TRUE
-- 
2.7.4