Seems smart to do.

Reviewed-by: Andrei Warkentin <awarkentin@vmware.com>
________________________________
From: Jeremy Linton <jeremy.linton@arm.com>
Sent: Friday, October 1, 2021 7:52 PM
To: devel@edk2.groups.io <devel@edk2.groups.io>
Cc: pete@akeo.ie <pete@akeo.ie>; ardb+tianocore@kernel.org <ardb+tianocore@kernel.org>; leif@nuviainc.com <leif@nuviainc.com>; Andrei Warkentin <awarkentin@vmware.com>; Sunny.Wang@arm.com <Sunny.Wang@arm.com>; samer.el-haj-mahmoud@arm.com <samer.el-haj-mahmoud@arm.com>; Jeremy Linton <jeremy.linton@arm.com>
Subject: [PATCH 5/5] Platform/RaspberryPi: Disconnect/shutdown all drivers before reboot

In theory we should be properly cleaning up all the device drivers before
pulling the big switch. Particularly the partition mgr will issue
flush commands to attached disks as it goes down. This assures that
devices running in WB mode (that correctly handle flush/sync/etc) commands
are persisted to physical media before we hit reset.

Without this, there are definitly cases where the relevant specifications
don't guarantee persistence of data in their buffers in the face of
reset conditions. We can't really do anything about the many
devices that don't honor persistance requests but we can start here.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
---
 Platform/RaspberryPi/Library/ResetLib/ResetLib.c | 44 ++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Platform/RaspberryPi/Library/ResetLib/ResetLib.c b/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
index a70eee485d..036f619cb5 100644
--- a/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
+++ b/Platform/RaspberryPi/Library/ResetLib/ResetLib.c
@@ -19,11 +19,54 @@
 #include <Library/TimerLib.h>
 #include <Library/EfiResetSystemLib.h>
 #include <Library/ArmSmcLib.h>
+#include <Library/UefiBootServicesTableLib.h>
 #include <Library/UefiLib.h>
 #include <Library/UefiRuntimeLib.h>

 #include <IndustryStandard/ArmStdSmc.h>

+
+/**
+  Disconnect everything.
+  Modified from the UEFI 2.3 spec (May 2009 version)
+
+  @retval EFI_SUCCESS     The operation was successful.
+
+**/
+EFI_STATUS
+DisconnectAll(
+  VOID
+  )
+{
+  EFI_STATUS Status;
+  UINTN HandleCount;
+  EFI_HANDLE *HandleBuffer;
+  UINTN HandleIndex;
+
+  //
+  // Retrieve the list of all handles from the handle database
+  //
+  Status = gBS->LocateHandleBuffer (
+    AllHandles,
+    NULL,
+    NULL,
+    &HandleCount,
+    &HandleBuffer
+   );
+  if (!EFI_ERROR (Status)) {
+    for (HandleIndex = 0; HandleIndex < HandleCount; HandleIndex++) {
+      Status = gBS->DisconnectController (
+        HandleBuffer[HandleIndex],
+        NULL,
+        NULL
+       );
+    }
+    gBS->FreePool(HandleBuffer);
+  }
+  return (EFI_SUCCESS);
+}
+
+
 /**
   Resets the entire platform.

@@ -57,6 +100,7 @@ LibResetSystem (
     if (Delay != 0) {
       DEBUG ((DEBUG_INFO, "Platform will be reset in %d.%d seconds...\n",
               Delay / 1000000, (Delay % 1000000) / 100000));
+      DisconnectAll ();
       MicroSecondDelay (Delay);
     }
   }
--
2.13.7