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* [edk2-devel] [PATCH] ArmPlatformPkg/PL031RealTimeClockLib: remove superfluous instance init steps
@ 2023-10-20 12:17 Laszlo Ersek
  2023-10-20 12:27 ` Ard Biesheuvel
  0 siblings, 1 reply; 3+ messages in thread
From: Laszlo Ersek @ 2023-10-20 12:17 UTC (permalink / raw)
  To: devel; +Cc: Ard Biesheuvel, Leif Lindholm

RealTimeClockLib instances are consumed by edk2's
EmbeddedPkg/RealTimeClockRuntimeDxe driver. In its entry point function
InitializeRealTimeClock(), the driver:

(1) calls LibRtcInitialize(),

(2) sets the GetTime(), SetTime(), GetWakeupTime() and SetWakeupTime()
    runtime services to its own similarly-named functions -- where those
    functions wrap the corresponding RealTimeClockLib APIs,

(3) installs EFI_REAL_TIME_CLOCK_ARCH_PROTOCOL with a NULL protocol
    interface.

Steps (2) and (3) conform to PI v1.8 sections II-9.7.2.4 through
II-9.7.2.7.

However, this means that LibRtcInitialize() (of any RealTimeClockLib
instance) should not itself (a) set the GetTime(), SetTime(),
GetWakeupTime() and SetWakeupTime() runtime services, nor (b) install
EFI_REAL_TIME_CLOCK_ARCH_PROTOCOL. The runtime service pointers will be
overwritten in step (2) anyway, and step (3) will uselessly install a
second (NULL-interface) EFI_REAL_TIME_CLOCK_ARCH_PROTOCOL instance in the
protocol database. (The protocol only serves to notify the DXE Foundation
about said runtime services being available.)

Clean up ArmPlatformPkg/PL031RealTimeClockLib accordingly (it only has
code that's redundant for step (3); it does not try to set "gRT" fields).

(Note that the lib instance INF file already does not list
gEfiRealTimeClockArchProtocolGuid.)

Tested with ArmVirtQemu.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=4565
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    context:-W

 ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c b/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
index 9e852696d2fd..1896f9d16d3b 100644
--- a/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
+++ b/ArmPlatformPkg/Library/PL031RealTimeClockLib/PL031RealTimeClockLib.c
@@ -1,34 +1,32 @@
 /** @file
   Implement EFI RealTimeClock runtime services via RTC Lib.
 
   Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
   Copyright (c) 2011 - 2020, Arm Limited. All rights reserved.<BR>
   Copyright (c) 2019, Linaro Ltd. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
 #include <PiDxe.h>
 
 #include <Guid/EventGroup.h>
 #include <Guid/GlobalVariable.h>
 
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
 #include <Library/DxeServicesTableLib.h>
 #include <Library/IoLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/PcdLib.h>
 #include <Library/RealTimeClockLib.h>
 #include <Library/TimeBaseLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/UefiLib.h>
 #include <Library/UefiRuntimeServicesTableLib.h>
 #include <Library/UefiRuntimeLib.h>
 
-#include <Protocol/RealTimeClock.h>
-
 #include "PL031RealTimeClock.h"
 
 STATIC BOOLEAN    mPL031Initialized = FALSE;
@@ -307,52 +305,41 @@ EFIAPI
 LibRtcInitialize (
   IN EFI_HANDLE        ImageHandle,
   IN EFI_SYSTEM_TABLE  *SystemTable
   )
 {
   EFI_STATUS  Status;
-  EFI_HANDLE  Handle;
 
   // Initialize RTC Base Address
   mPL031RtcBase = PcdGet32 (PcdPL031RtcBase);
 
   // Declare the controller as EFI_MEMORY_RUNTIME
   Status = gDS->AddMemorySpace (
                   EfiGcdMemoryTypeMemoryMappedIo,
                   mPL031RtcBase,
                   SIZE_4KB,
                   EFI_MEMORY_UC | EFI_MEMORY_RUNTIME
                   );
   if (EFI_ERROR (Status)) {
     return Status;
   }
 
   Status = gDS->SetMemorySpaceAttributes (mPL031RtcBase, SIZE_4KB, EFI_MEMORY_UC | EFI_MEMORY_RUNTIME);
   if (EFI_ERROR (Status)) {
     return Status;
   }
 
-  // Install the protocol
-  Handle = NULL;
-  Status = gBS->InstallMultipleProtocolInterfaces (
-                  &Handle,
-                  &gEfiRealTimeClockArchProtocolGuid,
-                  NULL,
-                  NULL
-                  );
-  ASSERT_EFI_ERROR (Status);
-
   //
   // Register for the virtual address change event
   //
   Status = gBS->CreateEventEx (
                   EVT_NOTIFY_SIGNAL,
                   TPL_NOTIFY,
                   VirtualNotifyEvent,
                   NULL,
                   &gEfiEventVirtualAddressChangeGuid,
                   &mRtcVirtualAddrChangeEvent
                   );
   ASSERT_EFI_ERROR (Status);
 
   return Status;
 }


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Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2023-10-20 12:17 [edk2-devel] [PATCH] ArmPlatformPkg/PL031RealTimeClockLib: remove superfluous instance init steps Laszlo Ersek
2023-10-20 12:27 ` Ard Biesheuvel
2023-10-24 16:50   ` Laszlo Ersek

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