Add a PCD to govern whether to use DT or ACPI in case the
variable governing this is not found or is not valid.

Signed-off-by: Ashish Singhal <ashishsingha@nvidia.com>
---
 EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.c   | 16 ++++++++++------
 EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.inf |  3 +++
 EmbeddedPkg/EmbeddedPkg.dec                         |  5 +++++
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.c b/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.c
index 907d46a..e35ca33 100644
--- a/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.c
+++ b/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.c
@@ -124,18 +124,22 @@ DtPlatformDxeEntryPoint (
     Status = gRT->GetVariable(DT_ACPI_VARIABLE_NAME, &gDtPlatformFormSetGuid,
                     NULL, &BufferSize, &DtAcpiPref);
     if (EFI_ERROR (Status)) {
-      DEBUG ((DEBUG_WARN, "%a: no DT/ACPI preference found, defaulting to DT\n",
-        __FUNCTION__));
-      DtAcpiPref.Pref = DT_ACPI_SELECT_DT;
+      DEBUG ((DEBUG_WARN, "%a: no DT/ACPI preference found, defaulting to %s\n",
+        __FUNCTION__, PcdGetBool (PcdDefaultDtPref) ? L"DT" : L"ACPI"));
+      DtAcpiPref.Pref = PcdGetBool (PcdDefaultDtPref) ?
+                          DT_ACPI_SELECT_DT :
+                          DT_ACPI_SELECT_ACPI;
     }
   }
 
   if (!EFI_ERROR (Status) &&
       DtAcpiPref.Pref != DT_ACPI_SELECT_ACPI &&
       DtAcpiPref.Pref != DT_ACPI_SELECT_DT) {
-    DEBUG ((DEBUG_WARN, "%a: invalid value for %s, defaulting to DT\n",
-      __FUNCTION__, DT_ACPI_VARIABLE_NAME));
-    DtAcpiPref.Pref = DT_ACPI_SELECT_DT;
+    DEBUG ((DEBUG_WARN, "%a: invalid value for %s, defaulting to %s\n",
+      __FUNCTION__, DT_ACPI_VARIABLE_NAME, PcdGetBool (PcdDefaultDtPref) ? L"DT" : L"ACPI"));
+    DtAcpiPref.Pref = PcdGetBool (PcdDefaultDtPref) ?
+                        DT_ACPI_SELECT_DT :
+                        DT_ACPI_SELECT_ACPI;
     Status = EFI_INVALID_PARAMETER; // trigger setvar below
   }
 
diff --git a/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.inf b/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.inf
index b68f154..450ea29 100644
--- a/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.inf
+++ b/EmbeddedPkg/Drivers/DtPlatformDxe/DtPlatformDxe.inf
@@ -46,6 +46,9 @@
   gEdkiiPlatformHasAcpiGuid
   gFdtTableGuid
 
+[Pcd]
+  gEmbeddedTokenSpaceGuid.PcdDefaultDtPref
+
 [Depex]
   gEfiVariableArchProtocolGuid        AND
   gEfiVariableWriteArchProtocolGuid
diff --git a/EmbeddedPkg/EmbeddedPkg.dec b/EmbeddedPkg/EmbeddedPkg.dec
index bbaadc5..8812a6d 100644
--- a/EmbeddedPkg/EmbeddedPkg.dec
+++ b/EmbeddedPkg/EmbeddedPkg.dec
@@ -185,3 +185,8 @@
   # truncation on overflow to specify negative offsets.
   #
   gEmbeddedTokenSpaceGuid.PcdDmaDeviceOffset|0x0|UINT64|0x0000058
+
+  #
+  # Selection between DT and ACPI as a default
+  #
+  gEmbeddedTokenSpaceGuid.PcdDefaultDtPref|TRUE|BOOLEAN|0x0000059
-- 
2.7.4


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