[edk2-platforms][PATCH 1/1] Platform/RaspberryPi: Add system/user defined reset delay

["Pete Batard" <pete@akeo.ie>]

Due to the method in which NV variables are stored on removable media
for the Raspberry Pi platform, and the manner in which we dump updated
variables right before reset, it is possible, and has been repeatedly
demonstrated with SSD-based USB 3.0 devices, that the updated file does
not actually end up being written to permanent storage, due to the
device write-cache not having enough time to be flushed before reset.

To compensate for this, since we don't know of a generic method that
would allow turning off USB mass storage devices write cache (and also
because we are seeing an issue that seems related for SD-based media),
we add a new reset delay PCD, which can be set by the user, and which
we also set as required when NV variables are being dumped.

Our testing show that, with more than 3 seconds of extra delay, the
storage media has enough time to finalize its internal write, thus
solving the issue of configuration changes not being persisted.

Signed-off-by: Pete Batard <pete@akeo.ie>
---
 Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.c   | 24 ++++++++++++++++++++
 Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.inf |  1 +
 Platform/RaspberryPi/Library/ResetLib/ResetLib.c                       | 11 +++++++++
 Platform/RaspberryPi/Library/ResetLib/ResetLib.inf                     |  5 ++++
 Platform/RaspberryPi/RPi3/RPi3.dsc                                     |  6 +++++
 Platform/RaspberryPi/RPi4/RPi4.dsc                                     |  6 +++++
 Platform/RaspberryPi/RaspberryPi.dec                                   |  1 +
 7 files changed, 54 insertions(+)

diff --git a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.c b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.c
index 07f3f1c24295..4071a3fca468 100644
--- a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.c
+++ b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.c
@@ -10,6 +10,18 @@
 
 #include "VarBlockService.h"
 
+//
+// Minimum delay to enact before reset, when variables are dirty (in μs).
+// Needed to ensure that SSD-based USB 3.0 devices have time to flush their
+// write cache after updating the NV vars. A much smaller delay is applied
+// on Pi 3 compared to Pi 4, as we haven't had reports of issues there yet.
+//
+#if (RPI_MODEL == 3)
+#define PLATFORM_RESET_DELAY     500000
+#else
+#define PLATFORM_RESET_DELAY    3500000
+#endif
+
 VOID *mSFSRegistration;
 
 
@@ -154,6 +166,7 @@ DumpVars (
   )
 {
   EFI_STATUS Status;
+  RETURN_STATUS PcdStatus;
 
   if (mFvInstance->Device == NULL) {
     DEBUG ((DEBUG_INFO, "Variable store not found?\n"));
@@ -173,6 +186,17 @@ DumpVars (
   }
 
   DEBUG ((DEBUG_INFO, "Variables dumped!\n"));
+
+  //
+  // Add a reset delay to give time for slow/cached devices
+  // to flush the NV variables write to permanent storage.
+  // But only do so if this won't reduce an existing user-set delay.
+  //
+  if (PcdGet32 (PcdPlatformResetDelay) < PLATFORM_RESET_DELAY) {
+    PcdStatus = PcdSet32S (PcdPlatformResetDelay, PLATFORM_RESET_DELAY);
+    ASSERT_RETURN_ERROR (PcdStatus);
+  }
+
   mFvInstance->Dirty = FALSE;
 }
 
diff --git a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.inf b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.inf
index ecfb8f85c9c1..c2edb25bd41d 100644
--- a/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.inf
+++ b/Platform/RaspberryPi/Drivers/VarBlockServiceDxe/VarBlockServiceDxe.inf
@@ -79,6 +79,7 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareBase
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase
   gRaspberryPiTokenSpaceGuid.PcdNvStorageEventLogBase
+  gRaspberryPiTokenSpaceGuid.PcdPlatformResetDelay
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase64
 
 [FeaturePcd]
diff --git a/Platform/RaspberryPi/Library/ResetLib/ResetLib.c b/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
index c62a92321ecb..4a50166dd63b 100644
--- a/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
+++ b/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
@@ -16,6 +16,7 @@
 
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
+#include <Library/TimerLib.h>
 #include <Library/EfiResetSystemLib.h>
 #include <Library/ArmSmcLib.h>
 #include <Library/UefiLib.h>
@@ -44,6 +45,7 @@ LibResetSystem (
   )
 {
   ARM_SMC_ARGS ArmSmcArgs;
+  UINT32 Delay;
 
   if (!EfiAtRuntime ()) {
     /*
@@ -52,6 +54,15 @@ LibResetSystem (
     EfiEventGroupSignal (&gRaspberryPiEventResetGuid);
   }
 
+  Delay = PcdGet32 (PcdPlatformResetDelay);
+  if (Delay != 0) {
+    DEBUG ((DEBUG_INFO, "Platform will be reset in %d.%d seconds...\n",
+            Delay / 1000000, (Delay % 1000000) / 100000));
+    MicroSecondDelay (Delay);
+  }
+  DEBUG ((DEBUG_INFO, "Platform %a.\n",
+          (ResetType == EfiResetShutdown) ? "shutdown" : "reset"));
+
   switch (ResetType) {
   case EfiResetPlatformSpecific:
     // Map the platform specific reset as reboot
diff --git a/Platform/RaspberryPi/Library/ResetLib/ResetLib.inf b/Platform/RaspberryPi/Library/ResetLib/ResetLib.inf
index b02a06d9d0bf..9bdb94a52ebf 100644
--- a/Platform/RaspberryPi/Library/ResetLib/ResetLib.inf
+++ b/Platform/RaspberryPi/Library/ResetLib/ResetLib.inf
@@ -33,8 +33,13 @@ [LibraryClasses]
   DebugLib
   BaseLib
   ArmSmcLib
+  PcdLib
+  TimerLib
   UefiLib
   UefiRuntimeLib
 
 [Guids]
   gRaspberryPiEventResetGuid
+
+[Pcd]
+  gRaspberryPiTokenSpaceGuid.PcdPlatformResetDelay      ## CONSUMES
diff --git a/Platform/RaspberryPi/RPi3/RPi3.dsc b/Platform/RaspberryPi/RPi3/RPi3.dsc
index 9408138d0a09..530b42796a0d 100644
--- a/Platform/RaspberryPi/RPi3/RPi3.dsc
+++ b/Platform/RaspberryPi/RPi3/RPi3.dsc
@@ -508,6 +508,12 @@ [PcdsDynamicHii.common.DEFAULT]
   gRaspberryPiTokenSpaceGuid.PcdFanOnGpio|L"FanOnGpio"|gConfigDxeFormSetGuid|0x0|0
   gRaspberryPiTokenSpaceGuid.PcdFanTemp|L"FanTemp"|gConfigDxeFormSetGuid|0x0|0
 
+  #
+  # Reset-related.
+  #
+
+  gRaspberryPiTokenSpaceGuid.PcdPlatformResetDelay|L"ResetDelay"|gRaspberryPiTokenSpaceGuid|0x0|0
+
   #
   # Common UEFI ones.
   #
diff --git a/Platform/RaspberryPi/RPi4/RPi4.dsc b/Platform/RaspberryPi/RPi4/RPi4.dsc
index ddf4dd6a416e..5f8452aa0b76 100644
--- a/Platform/RaspberryPi/RPi4/RPi4.dsc
+++ b/Platform/RaspberryPi/RPi4/RPi4.dsc
@@ -522,6 +522,12 @@ [PcdsDynamicHii.common.DEFAULT]
   gRaspberryPiTokenSpaceGuid.PcdFanOnGpio|L"FanOnGpio"|gConfigDxeFormSetGuid|0x0|0
   gRaspberryPiTokenSpaceGuid.PcdFanTemp|L"FanTemp"|gConfigDxeFormSetGuid|0x0|60
 
+  #
+  # Reset-related.
+  #
+
+  gRaspberryPiTokenSpaceGuid.PcdPlatformResetDelay|L"ResetDelay"|gRaspberryPiTokenSpaceGuid|0x0|0
+
   #
   # Common UEFI ones.
   #
diff --git a/Platform/RaspberryPi/RaspberryPi.dec b/Platform/RaspberryPi/RaspberryPi.dec
index c64c61930ea8..10723036aa31 100644
--- a/Platform/RaspberryPi/RaspberryPi.dec
+++ b/Platform/RaspberryPi/RaspberryPi.dec
@@ -68,3 +68,4 @@ [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   gRaspberryPiTokenSpaceGuid.PcdRamLimitTo3GB|0|UINT32|0x0000001A
   gRaspberryPiTokenSpaceGuid.PcdFanOnGpio|0|UINT32|0x0000001C
   gRaspberryPiTokenSpaceGuid.PcdFanTemp|0|UINT32|0x0000001D
+  gRaspberryPiTokenSpaceGuid.PcdPlatformResetDelay|0|UINT32|0x0000001E
-- 
2.29.2.windows.2