ArmVirtPkg/FdtClientDxe: install DT configuration table at ReadyToBoot

Defer FDT configuration table installation until ReadyToBoot is signaled.
This allows any driver to make modifications in the mean time, and will
also allow us to defer the decision of whether to install it in the first
place to later on in the boot.

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

ArmVirtPkg/FdtClientDxe/FdtClientDxe.c

@@ -20,6 +20,7 @@
 #include <Library/HobLib.h>
 #include <libfdt.h>
 
+#include <Guid/EventGroup.h>
 #include <Guid/Fdt.h>
 #include <Guid/FdtHob.h>
 
@@ -306,6 +307,30 @@ STATIC FDT_CLIENT_PROTOCOL mFdtClientProtocol = {
   GetOrInsertChosenNode,
 };
 
+STATIC
+VOID
+EFIAPI
+OnReadyToBoot (
+  EFI_EVENT       Event,
+  VOID            *Context
+  )
+{
+  EFI_STATUS      Status;
+
+  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.
+    //
+    Status = gBS->InstallConfigurationTable (&gFdtTableGuid, mDeviceTreeBase);
+    ASSERT_EFI_ERROR (Status);
+  }
+
+  gBS->CloseEvent (Event);
+}
+
+STATIC EFI_EVENT         mReadyToBootEvent;
+
 EFI_STATUS
 EFIAPI
 InitializeFdtClientDxe (
@@ -333,15 +358,21 @@ InitializeFdtClientDxe (
 
   DEBUG ((EFI_D_INFO, "%a: DTB @ 0x%p\n", __FUNCTION__, mDeviceTreeBase));
 
-  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.
-    //
-    Status = gBS->InstallConfigurationTable (&gFdtTableGuid, DeviceTreeBase);
-    ASSERT_EFI_ERROR (Status);
+  Status = gBS->InstallProtocolInterface (&ImageHandle, &gFdtClientProtocolGuid,
+                  EFI_NATIVE_INTERFACE, &mFdtClientProtocol);
+  if (EFI_ERROR (Status)) {
+    return Status;
   }
 
-  return gBS->InstallProtocolInterface (&ImageHandle, &gFdtClientProtocolGuid,
-                EFI_NATIVE_INTERFACE, &mFdtClientProtocol);
+  Status = gBS->CreateEventEx (
+                  EVT_NOTIFY_SIGNAL,
+                  TPL_CALLBACK,
+                  OnReadyToBoot,
+                  NULL,
+                  &gEfiEventReadyToBootGuid,
+                  &mReadyToBootEvent
+                  );
+  ASSERT_EFI_ERROR (Status);
+
+  return EFI_SUCCESS;
 }

ArmVirtPkg/FdtClientDxe/FdtClientDxe.inf

@@ -42,6 +42,7 @@
   gFdtClientProtocolGuid                  ## PRODUCES
 
 [Guids]
+  gEfiEventReadyToBootGuid
   gFdtHobGuid
   gFdtTableGuid