Re: [edk2-devel] [PATCH v1 1/1] StandaloneMmPkg: Initialise serial port early in StandaloneMmEntryPoint

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

On Fri, 5 Jan 2024 at 12:49, levi.yun <yeoreum.yun@arm.com> wrote:
>
> Serial port used by the DEBUG macro is initialised in StandaloneMmMain
> by the DebugLib constructor.
>
> When we use a serial port initialised by TF-A it is not a problem.
> However, if we use a serial port that is not initialised by TF-A,
> the debug log prints hangs.
>
> Therefore, initialise the serial port early on in the entry point.
>
> Signed-off-by: levi.yun <yeoreum.yun@arm.com>
> ---
> These changes can be seen at
> https://github.com/LeviYeoReum/edk2/tree/levi/2956_init_serial too.
>

So now we will always initialize the serial port in the entrypoint
only because DebugLib might use it later with doing the
initialization.

That doesn't sound quite correct to me.

Could you explain why we cannot rely on DebugLib to call the
initializer / constructor at the right time?



>  StandaloneMmPkg/StandaloneMmPkg.dsc                                                 | 1 +
>  StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf   | 1 +
>  StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/Arm/StandaloneMmCoreEntryPoint.c | 3 +++
>  3 files changed, 5 insertions(+)
>
> diff --git a/StandaloneMmPkg/StandaloneMmPkg.dsc b/StandaloneMmPkg/StandaloneMmPkg.dsc
> index 8012f93b7dcc38ea8fdd2de98912bbc09157ec53..040a4aa5b3d268fdfaaec9a975cfc6ff31aa37b4 100644
> --- a/StandaloneMmPkg/StandaloneMmPkg.dsc
> +++ b/StandaloneMmPkg/StandaloneMmPkg.dsc
> @@ -66,6 +66,7 @@ [LibraryClasses.AARCH64, LibraryClasses.ARM]
>    ArmSvcLib|ArmPkg/Library/ArmSvcLib/ArmSvcLib.inf
>    CacheMaintenanceLib|ArmPkg/Library/ArmCacheMaintenanceLib/ArmCacheMaintenanceLib.inf
>    PeCoffExtraActionLib|StandaloneMmPkg/Library/StandaloneMmPeCoffExtraActionLib/StandaloneMmPeCoffExtraActionLib.inf
> +  SerialPortLib|MdePkg/Library/BaseSerialPortLibNull/BaseSerialPortLibNull.inf
>
>    NULL|ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrinsicsLib.inf
>    NULL|MdePkg/Library/BaseStackCheckLib/BaseStackCheckLib.inf
> diff --git a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
> index 75cfb98c0e75cd7cee2a59723035679612da4528..086639ecfbc983627aed73817815e2485104375e 100644
> --- a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
> +++ b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/StandaloneMmCoreEntryPoint.inf
> @@ -42,6 +42,7 @@ [LibraryClasses]
>    DebugLib
>
>  [LibraryClasses.ARM, LibraryClasses.AARCH64]
> +  SerialPortLib
>    StandaloneMmMmuLib
>    ArmSvcLib
>
> diff --git a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/Arm/StandaloneMmCoreEntryPoint.c b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/Arm/StandaloneMmCoreEntryPoint.c
> index 96de10405af829c66e3f43ed4692f785d8df113e..66b56bdfe4959d5ab6152ff024caa6e900e7a948 100644
> --- a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/Arm/StandaloneMmCoreEntryPoint.c
> +++ b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/Arm/StandaloneMmCoreEntryPoint.c
> @@ -335,6 +335,9 @@ _ModuleEntryPoint (
>    UINTN                           TeDataSize;
>    EFI_PHYSICAL_ADDRESS            ImageBase;
>
> +  // Initialize the Serial Port early to print debug log before StandaloneMmMain.
> +  SerialPortInitialize ();
> +
>    // Get Secure Partition Manager Version Information
>    Status = GetSpmVersion ();
>    if (EFI_ERROR (Status)) {
> --
> Guid("CE165669-3EF3-493F-B85D-6190EE5B9759")
>
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>
>
> 
>
>


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