Re: [PATCH 05/10] StandaloneMmPkg/StandaloneMmCoreEntryPoint: drop explicit SerialPortLib call

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Wed, 6 Mar 2019 at 17:35, Achin Gupta <Achin.Gupta@arm.com> wrote:
>
> Hi Ard,
>
> On Tue, Mar 05, 2019 at 02:32:43PM +0100, Ard Biesheuvel wrote:
> > Sending DEBUG output to the serial port should only be done via
> > DebugLib calls, which is in charge of initializing the serial
> > port when appropriate. So drop the explicit SerialPortInitialize ()
> > invocation, and rely on normal constructor ordering to get the
> > serial port into the appropriate state at the right time.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >  StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c | 3 ---
> >  1 file changed, 3 deletions(-)
> >
> > diff --git a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
> > index 5cca532456fd..c8e11a253d24 100644
> > --- a/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
> > +++ b/StandaloneMmPkg/Library/StandaloneMmCoreEntryPoint/AArch64/StandaloneMmCoreEntryPoint.c
> > @@ -232,9 +232,6 @@ _ModuleEntryPoint (
> >    VOID                                    *TeData;
> >    UINTN                                   TeDataSize;
> >
> > -  Status = SerialPortInitialize ();
> > -  ASSERT_EFI_ERROR (Status);
>
> This is done in the first few instructions after EL3 ERETs into S-EL0 to
> initialise the StMM partition. The constructors will be called a bit later. I
> agree with the change but does EDK2 provide a mechanism for early prints to the
> console in case we need this in future.
>

If so, the correct way to achieve this would be to call the DebugLib
constructor by hand, and that should call the SerialPortLib
constructor. Unfortunately, EDK2 is not put together like that, and
especially constructor ordering is slightly broken.