[edk2-platform PATCH v1 1/1] Platform/RaspberryPi: Make SetVariable return EFI_UNSUPPORTED at runtime

["Sunny Wang" <Sunny.Wang@arm.com>]

The RPi does not support storing UEFI NV variables at runtime. For now,
gRT->SetVariable at runtime returns EFI_OUT_OF_RESOURCES which is not a
proper error and would cause FWTS failures. Therefore, this patch is
to make gRT->SetVariable at runtime return EFI_UNSUPPORTED.

For more information, please check the issues below:
   -https://github.com/pftf/RPi4/issues/6
   -https://github.com/pftf/RPi4/issues/93
   -https://github.com/pftf/RPi4/issues/163

I also tested this with the ACS 3.0 FWTS. All the failures
reported in issue 93 and 163 can be fixed by this patch.

Cc: Samer El-Haj-Mahmoud <samer.el-haj-mahmoud@arm.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Pete Batard <pete@akeo.ie>
Cc: Leif Lindholm <leif@nuviainc.com>

Signed-off-by: Sunny Wang <sunny.wang@arm.com>
---
 .../Drivers/VarBlockServiceDxe/VarBlockService.c     | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockService.c b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockService.c
index 572309439a..16d4d4f178 100644
--- a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockService.c
+++ b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockService.c
@@ -2,6 +2,7 @@
  *
  *  Copyright (c) 2018, Andrei Warkentin <andrey.warkentin@gmail.com>
  *  Copyright (c) 2006-2014, Intel Corporation. All rights reserved.
+ *  Copyright (c) 2021, ARM Limited. All rights reserved.
  *
  *  SPDX-License-Identifier: BSD-2-Clause-Patent
  *
@@ -596,6 +597,7 @@ FvbProtocolWrite (
     EFI_DEVICE_ERROR      - The block device is not functioning correctly and
                             could not be written
     EFI_INVALID_PARAMETER - NumBytes or Buffer are NULL
+    EFI_UNSUPPORTED         This function is not supported at runtime
 
 --*/
 {
@@ -605,6 +607,16 @@ FvbProtocolWrite (
   EFI_STATUS Status;
   EFI_STATUS ReturnStatus;
 
+  //
+  // The current variables support relies on modifying RPI_EFI.FD on SD
+  // card, which works fine at boot time. However, at runtime, the SD 
+  // controller is exposed via ACPI and subsequently owned by the OS.
+  // Therefore, we need to direclty return EFI_UNSUPPORTED.
+  //
+  if (EfiAtRuntime ()) {
+   return EFI_UNSUPPORTED;
+  }
+
   //
   // Check for invalid conditions.
   //
-- 
2.31.0.windows.1