Re: [edk2-devel] [PATCH] ArmPlatformPkg/PL031RealTimeClockLib: remove superfluous instance init steps

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 20 Oct 2023 at 14:17, Laszlo Ersek <lersek@redhat.com> wrote:
>
> 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(-)
>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Thanks a lot for cleaning up this mess.


> 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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