Re: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for RISC-V

["Andrei Warkentin" <andrei.warkentin@intel.com>]

So I'd be in support of formally defining a PrePi prefix. If we go with Sec, then we'd have to come up with some other way of disambiguating "hand off to PEI" vs "hand off to DXE", and it seems like PrePi is already that.

What do you entail the process to be followed here? Is there value in defining a dedicated PrePi module type (like SEC)? I'd be happy to propose the edk2 changes to support that. Can we decouple this work from these specific SerialPortLib contributions?

A

-----Original Message-----
From: Kinney, Michael D <michael.d.kinney@intel.com> 
Sent: Tuesday, March 28, 2023 3:10 PM
To: Warkentin, Andrei <andrei.warkentin@intel.com>; devel@edk2.groups.io
Cc: Gao, Liming <gaoliming@byosoft.com.cn>; Liu, Zhiguang <zhiguang.liu@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>
Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for RISC-V

I agree that moving into EmbeddedPkg does not make sense.

EmbeddedPkg is very old without many updates.  That package is not the best to use for examples.

I think you are suggesting that there is a difference in a library that runs in an SEC env with intent to hand off to PEI and a library that runs in an SEC env with intent to handoff to DXE.  They are both SEC module types and the execution environment is the same.  The only difference is how they prepare for the handoff.

My interest here is to make sure the prefixes are used consistently and if we truly have a new prefix type, then to clearly define it so it can be used consistently going forward.

Mike 

> -----Original Message-----
> From: Warkentin, Andrei <andrei.warkentin@intel.com>
> Sent: Tuesday, March 28, 2023 1:00 PM
> To: Kinney, Michael D <michael.d.kinney@intel.com>; 
> devel@edk2.groups.io
> Cc: Gao, Liming <gaoliming@byosoft.com.cn>; Liu, Zhiguang 
> <zhiguang.liu@intel.com>
> Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for 
> RISC-V
> 
> Sec isn't a good fit, because it has implications on the environment, 
> which is why the contribution also includes a separate SecPei variant as well.
> 
> In naming, I followed other edk2 examples such as 
> ./EmbeddedPkg/Library/PrePiExtractGuidedSectionLib and 
> ./EmbeddedPkg/Library/PrePiMemoryAllocationLi. I would prefer not to move one of these libraries into EmbeddedPkg - that wouldn't make much sense to me (esp. since there's nothing "embedded" about the approach per se, it can be used on any implementation).
> 
> A
> -----Original Message-----
> From: Kinney, Michael D <michael.d.kinney@intel.com>
> Sent: Monday, March 27, 2023 11:32 AM
> To: Warkentin, Andrei <andrei.warkentin@intel.com>; 
> devel@edk2.groups.io
> Cc: Gao, Liming <gaoliming@byosoft.com.cn>; Liu, Zhiguang 
> <zhiguang.liu@intel.com>; Kinney, Michael D 
> <michael.d.kinney@intel.com>
> Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for 
> RISC-V
> 
> I think that would still be called Sec.  Are there any issues with using Sec prefix?
> 
> Mike
> 
> > -----Original Message-----
> > From: Warkentin, Andrei <andrei.warkentin@intel.com>
> > Sent: Thursday, March 16, 2023 10:45 PM
> > To: Kinney, Michael D <michael.d.kinney@intel.com>; 
> > devel@edk2.groups.io
> > Cc: Gao, Liming <gaoliming@byosoft.com.cn>; Liu, Zhiguang 
> > <zhiguang.liu@intel.com>
> > Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for 
> > RISC-V
> >
> > PrePi refers to a SEC-like stage in a Tiano implementation that 
> > skips the PEI stage. Reasons for skipping PEI usually center around 
> > memory initialization being done at an earlier stage of firmware 
> > initialization - for example, prior or part of TF-A firmware on
> > AArch64 or prior or part of SBI implementation on RISC-V.
> >
> > E.g. ArmVirtPkg/PrePi and OvmfPkg/RiscVVirt/Sec. The later is not a 
> > "SEC" in the send of handing off to PeiCore, but instead hands off to DxeCore.
> >
> > There is no base type for PrePi. The type is still SEC. But it a) assumes RAM is available b) builds HOBs and hands-off to DXE.
> >
> > The name has been around for at least half a decade now and making 
> > it a part of the SerialPortLib component name is important as it signifies the scenario where the code can apply.
> >
> > A
> >
> > -----Original Message-----
> > From: Kinney, Michael D <michael.d.kinney@intel.com>
> > Sent: Friday, March 17, 2023 12:01 AM
> > To: Warkentin, Andrei <andrei.warkentin@intel.com>; 
> > devel@edk2.groups.io
> > Cc: Gao, Liming <gaoliming@byosoft.com.cn>; Liu, Zhiguang 
> > <zhiguang.liu@intel.com>; Kinney, Michael D 
> > <michael.d.kinney@intel.com>
> > Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for 
> > RISC-V
> >
> > What is the definition of "PrePI"?  That is not a prefix I have seen used before.
> >
> > Mike
> >
> > > -----Original Message-----
> > > From: Warkentin, Andrei <andrei.warkentin@intel.com>
> > > Sent: Thursday, March 16, 2023 9:53 PM
> > > To: devel@edk2.groups.io
> > > Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming 
> > > <gaoliming@byosoft.com.cn>; Liu, Zhiguang <zhiguang.liu@intel.com>
> > > Subject: RE: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib 
> > > for RISC-V
> > >
> > > Hi folks,
> > >
> > > Can I get a review for the changes to MdePkg.dsc to include the 
> > > new libs on RISC-V? That's the minor thing preventing this patch set from being merged 😊.
> > >
> > > A
> > >
> > > -----Original Message-----
> > > From: Warkentin, Andrei <andrei.warkentin@intel.com>
> > > Sent: Friday, March 10, 2023 11:05 AM
> > > To: devel@edk2.groups.io
> > > Cc: Warkentin, Andrei <andrei.warkentin@intel.com>; Daniel 
> > > Schaefer <git@danielschaefer.me>; Sunil V L 
> > > <sunilvl@ventanamicro.com>; Kinney, Michael D 
> > > <michael.d.kinney@intel.com>; Gao, Liming 
> > > <gaoliming@byosoft.com.cn>; Liu, Zhiguang 
> > > <zhiguang.liu@intel.com>; Gerd Hoffmann <kraxel@redhat.com>
> > > Subject: [PATCH v5 2/3] MdePkg: add SBI-based SerialPortLib for 
> > > RISC-V
> > >
> > > These are implementations of SerialPortLib using SBI console services.
> > > - SecPeiRiscVSerialPortLibSbi is appropriate for SEC/PEI (XIP) 
> > > environments
> > > - PrePiDxeRiscVSerialPortLibSbi is appropriate for PrePI/DXE 
> > > environments
> > >
> > > Tested with:
> > > - Qemu RiscVVirt (non-DBCN case, backed by UART)
> > > - TinyEMU + RiscVVirt (non-DBCN case, HTIF)
> > > - TinyEMU + RiscVVirt (DBCN case, HTIF)
> > >
> > > Cc: Daniel Schaefer <git@danielschaefer.me>
> > > Cc: Sunil V L <sunilvl@ventanamicro.com>
> > > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > > Cc: Liming Gao <gaoliming@byosoft.com.cn>
> > > Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> > > Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> > > Signed-off-by: Andrei Warkentin <andrei.warkentin@intel.com>
> > > ---
> > >  MdePkg/MdePkg.dsc                                                              |   2 +
> > >  MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.inf |  36 +++
> > >  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.inf     |  39 +++
> > >  MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.c   | 288 ++++++++++++++++++++
> > >  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.c       | 233 ++++++++++++++++
> > >  MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.uni |  16 ++
> > >  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.uni     |  16 ++
> > >  7 files changed, 630 insertions(+)
> > >
> > > diff --git a/MdePkg/MdePkg.dsc b/MdePkg/MdePkg.dsc index 
> > > 0ac7618b4623..fb31349042fb 100644
> > > --- a/MdePkg/MdePkg.dsc
> > > +++ b/MdePkg/MdePkg.dsc
> > > @@ -192,5 +192,7 @@ [Components.ARM, Components.AARCH64]
> > >
> > >  [Components.RISCV64]
> > >    MdePkg/Library/BaseRiscVSbiLib/BaseRiscVSbiLib.inf
> > > +
> > > + MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > + Li
> > > + bS
> > > + bi
> > > + .inf
> > > + MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > + Po
> > > + rt
> > > + Li
> > > + bSbi.inf
> > >
> > >  [BuildOptions]
> > > diff --git
> > > a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.inf
> > > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.inf
> > > new file mode 100644
> > > index 000000000000..1d8544756bb9
> > > --- /dev/null
> > > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSe
> > > +++ ri
> > > +++ al
> > > +++ Po
> > > +++ rtLibSbi.inf
> > > @@ -0,0 +1,36 @@
> > > +## @file
> > > +#  Serial Port Library backed by SBI console.
> > > +#
> > > +#  Meant for PrePi and DXE environments (where globals are allowed).
> > > +See #  SecPeiSerialPortLibRiscVSbi for a reduced variant 
> > > +appropriate for SEC #  and PEI (XIP) environments.
> > > +#
> > > +#  Copyright (c) 2023, Intel Corporation. All rights 
> > > +reserved.<BR> # #
> > > +SPDX-License-Identifier: BSD-2-Clause-Patent # # ##
> > > +
> > > +[Defines]
> > > +  INF_VERSION                    = 0x0001001B
> > > +  BASE_NAME                      = PrePiDxeRiscVSerialPortLibSbi
> > > +  MODULE_UNI_FILE                = PrePiDxeRiscVSerialPortLibSbi.uni
> > > +  FILE_GUID                      = 872af743-ab56-45b4-a065-602567f4820c
> > > +  MODULE_TYPE                    = BASE
> > > +  VERSION_STRING                 = 1.0
> > > +  LIBRARY_CLASS                  = SerialPortLib | SEC DXE_CORE DXE_DRIVER DXE_RUNTIME_DRIVER UEFI_DRIVER UEFI_APPLICATION
> > > +
> > > +
> > > +#
> > > +#  VALID_ARCHITECTURES           = RISCV64
> > > +#
> > > +
> > > +[Sources]
> > > +  PrePiDxeRiscVSerialPortLibSbi.c
> > > +
> > > +[Packages]
> > > +  MdePkg/MdePkg.dec
> > > +
> > > +[LibraryClasses]
> > > +  RiscVSbiLib
> > > diff --git
> > > a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.inf
> > > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.inf
> > > new file mode 100644
> > > index 000000000000..7bc7cd47c11c
> > > --- /dev/null
> > > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerial
> > > +++ Po
> > > +++ rt
> > > +++ Li
> > > +++ bSbi.inf
> > > @@ -0,0 +1,39 @@
> > > +## @file
> > > +#  Serial Port Library backed by SBI console.
> > > +#
> > > +#  Meant for SEC and PEI (XIP) environments.
> > > +#
> > > +#  Due to limitations of SBI console interface and XIP 
> > > +environments # (on use of globals), this library instance does 
> > > +not implement reading # and polling the serial port. See 
> > > +PrePiDxeSerialPortLibRiscVSbi for # the full-featured variant meant for PrePi and DXE environments.
> > > +#
> > > +#  Copyright (c) 2023, Intel Corporation. All rights 
> > > +reserved.<BR> # #
> > > +SPDX-License-Identifier: BSD-2-Clause-Patent # # ##
> > > +
> > > +[Defines]
> > > +  INF_VERSION                    = 0x0001001B
> > > +  BASE_NAME                      = SecPeiRiscVSerialPortLibSbi
> > > +  MODULE_UNI_FILE                = SecPeiRiscVSerialPortLibSbi.uni
> > > +  FILE_GUID                      = 639fad38-4bfd-4eb9-9f09-e97c7947d480
> > > +  MODULE_TYPE                    = BASE
> > > +  VERSION_STRING                 = 1.0
> > > +  LIBRARY_CLASS                  = SerialPortLib | SEC PEI_CORE PEIM
> > > +
> > > +
> > > +#
> > > +#  VALID_ARCHITECTURES           = RISCV64
> > > +#
> > > +
> > > +[Sources]
> > > +  SecPeiRiscVSerialPortLibSbi.c
> > > +
> > > +[Packages]
> > > +  MdePkg/MdePkg.dec
> > > +
> > > +[LibraryClasses]
> > > +  RiscVSbiLib
> > > diff --git
> > > a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.c
> > > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.c
> > > new file mode 100644
> > > index 000000000000..058a6573ef2d
> > > --- /dev/null
> > > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSe
> > > +++ ri
> > > +++ al
> > > +++ Po
> > > +++ rtLibSbi.c
> > > @@ -0,0 +1,288 @@
> > > +/** @file
> > > +  Serial Port Library backed by SBI console.
> > > +
> > > +  Meant for PrePi and DXE environments (where globals are allowed).
> > > + See SecPeiSerialPortLibRiscVSbi for a reduced variant 
> > > + appropriate for SEC and PEI (XIP) environments.
> > > +
> > > +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> > > +  SPDX-License-Identifier: BSD-2-Clause-Patent
> > > +
> > > +**/
> > > +
> > > +#include <Base.h>
> > > +#include <Library/SerialPortLib.h> #include 
> > > +<Library/BaseRiscVSbiLib.h>
> > > +
> > > +STATIC BOOLEAN  mHaveDbcn          = FALSE;
> > > +STATIC BOOLEAN  mHaveLegacyPutchar = FALSE; STATIC BOOLEAN 
> > > +mHaveLegacyGetchar = FALSE;
> > > +STATIC INT64    mLastGetChar       = -1;
> > > +
> > > +/**
> > > +  Initialize the serial device hardware.
> > > +
> > > +  If no initialization is required, then return RETURN_SUCCESS.
> > > +  If the serial device was successfully initialized, then return RETURN_SUCCESS.
> > > +  If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.
> > > +
> > > +  @retval RETURN_SUCCESS        The serial device was initialized.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortInitialize (
> > > +  VOID
> > > +  )
> > > +{
> > > +  SBI_RET  Ret;
> > > +
> > > +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> > > + SBI_EXT_DBCN);  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +      (Ret.Value != 0))
> > > +  {
> > > +    mHaveDbcn = TRUE;
> > > +  } else {
> > > +    Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, SBI_EXT_0_1_CONSOLE_PUTCHAR);
> > > +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +        (Ret.Value != 0))
> > > +    {
> > > +      mHaveLegacyPutchar = TRUE;
> > > +    }
> > > +
> > > +    Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, SBI_EXT_0_1_CONSOLE_GETCHAR);
> > > +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +        (Ret.Value != 0))
> > > +    {
> > > +      mHaveLegacyGetchar = TRUE;
> > > +    }
> > > +  }
> > > +
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Write data from buffer to serial device.
> > > +
> > > +  Writes NumberOfBytes data bytes from Buffer to the serial device.
> > > +  The number of bytes actually written to the serial device is returned.
> > > +  If the return value is less than NumberOfBytes, then the write operation failed.
> > > +  If Buffer is NULL, then ASSERT().
> > > +  If NumberOfBytes is zero, then return 0.
> > > +
> > > +  @param  Buffer           The pointer to the data buffer to be written.
> > > +  @param  NumberOfBytes    The number of bytes to written to the serial device.
> > > +
> > > +  @retval 0                NumberOfBytes is 0.
> > > +  @retval >0               The number of bytes written to the serial device.
> > > +                           If this value is less than NumberOfBytes, then the write operation failed.
> > > +
> > > +**/
> > > +UINTN
> > > +EFIAPI
> > > +SerialPortWrite (
> > > +  IN UINT8  *Buffer,
> > > +  IN UINTN  NumberOfBytes
> > > +  )
> > > +{
> > > +  UINTN  Index;
> > > +
> > > +  if (mHaveDbcn) {
> > > +    SBI_RET  Ret;
> > > +    Ret = SbiCall (
> > > +            SBI_EXT_DBCN,
> > > +            SBI_EXT_DBCN_WRITE,
> > > +            3,
> > > +            NumberOfBytes,
> > > +            ((UINTN)Buffer),
> > > +            0
> > > +            );
> > > +    if (TranslateError (Ret.Error) != EFI_SUCCESS) {
> > > +      return 0;
> > > +    }
> > > +
> > > +    return Ret.Value;
> > > +  } else if (mHaveLegacyPutchar) {
> > > +    for (Index = 0; Index < NumberOfBytes; Index++) {
> > > +      SbiCall (SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, 1, Buffer[Index]);
> > > +    }
> > > +
> > > +    return Index;
> > > +  }
> > > +
> > > +  /*
> > > +   * Neither DBCN or legacy extension were present.
> > > +   */
> > > +  return NumberOfBytes;
> > > +}
> > > +
> > > +/**
> > > +  Read data from serial device and save the datas in buffer.
> > > +
> > > +  Reads NumberOfBytes data bytes from a serial device into the 
> > > + buffer specified by Buffer. The number of bytes actually read is returned.
> > > +  If the return value is less than NumberOfBytes, then the rest operation failed.
> > > +  If Buffer is NULL, then ASSERT().
> > > +  If NumberOfBytes is zero, then return 0.
> > > +
> > > +  @param  Buffer           The pointer to the data buffer to store the data read from the serial device.
> > > +  @param  NumberOfBytes    The number of bytes which will be read.
> > > +
> > > +  @retval 0                Read data failed; No data is to be read.
> > > +  @retval >0               The actual number of bytes read from serial device.
> > > +
> > > +**/
> > > +UINTN
> > > +EFIAPI
> > > +SerialPortRead (
> > > +  OUT UINT8  *Buffer,
> > > +  IN  UINTN  NumberOfBytes
> > > +  )
> > > +{
> > > +  UINTN  Index;
> > > +
> > > +  Index = 0;
> > > +  while ((Index < NumberOfBytes) && SerialPortPoll ()) {
> > > +    Buffer[Index++] = (UINT8)mLastGetChar;
> > > +    mLastGetChar    = -1;
> > > +  }
> > > +
> > > +  return Index;
> > > +}
> > > +
> > > +/**
> > > +  Polls a serial device to see if there is any data waiting to be read.
> > > +
> > > +  Polls a serial device to see if there is any data waiting to be read.
> > > +  If there is data waiting to be read from the serial device, then TRUE is returned.
> > > +  If there is no data waiting to be read from the serial device, then FALSE is returned.
> > > +
> > > +  @retval TRUE             Data is waiting to be read from the serial device.
> > > +  @retval FALSE            There is no data waiting to be read from the serial device.
> > > +
> > > +**/
> > > +BOOLEAN
> > > +EFIAPI
> > > +SerialPortPoll (
> > > +  VOID
> > > +  )
> > > +{
> > > +  /*
> > > +   * Careful. OpenSBI with HTIF console will return -1 followed by -2
> > > +   * if there is no character received. So just check for values >= 0.
> > > +   */
> > > +
> > > +  if (mLastGetChar >= 0) {
> > > +    return TRUE;
> > > +  }
> > > +
> > > +  if (mHaveDbcn) {
> > > +    UINT8    Buffer;
> > > +    SBI_RET  Ret;
> > > +
> > > +    Ret = SbiCall (
> > > +            SBI_EXT_DBCN,
> > > +            SBI_EXT_DBCN_READ,
> > > +            3,
> > > +            1,
> > > +            ((UINTN)&Buffer),
> > > +            0
> > > +            );
> > > +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +        (Ret.Value == 1))
> > > +    {
> > > +      mLastGetChar = Buffer;
> > > +    }
> > > +  } else if (mHaveLegacyGetchar) {
> > > +    mLastGetChar = (INT64)SbiCall (SBI_EXT_0_1_CONSOLE_GETCHAR, 
> > > + 0, 0).Error;  }
> > > +
> > > +  return mLastGetChar >= 0;
> > > +}
> > > +
> > > +/**
> > > +  Sets the control bits on a serial device.
> > > +
> > > +  @param Control                Sets the bits of Control that are settable.
> > > +
> > > +  @retval RETURN_SUCCESS        The new control bits were set on the serial device.
> > > +  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortSetControl (
> > > +  IN UINT32  Control
> > > +  )
> > > +{
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Retrieve the status of the control bits on a serial device.
> > > +
> > > +  @param Control                A pointer to return the current control signals from the serial device.
> > > +
> > > +  @retval RETURN_SUCCESS        The control bits were read from the serial device.
> > > +  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortGetControl (
> > > +  OUT UINT32  *Control
> > > +  )
> > > +{
> > > +  *Control = 0;
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Sets the baud rate, receive FIFO depth, transmit/receice time 
> > > +out, parity,
> > > +  data bits, and stop bits on a serial device.
> > > +
> > > +  @param BaudRate           The requested baud rate. A BaudRate value of 0 will use the
> > > +                            device's default interface speed.
> > > +                            On output, the value actually set.
> > > +  @param ReveiveFifoDepth   The requested depth of the FIFO on the receive side of the
> > > +                            serial interface. A ReceiveFifoDepth value of 0 will use
> > > +                            the device's default FIFO depth.
> > > +                            On output, the value actually set.
> > > +  @param Timeout            The requested time out for a single character in microseconds.
> > > +                            This timeout applies to both the transmit and receive side of the
> > > +                            interface. A Timeout value of 0 will use the device's default time
> > > +                            out value.
> > > +                            On output, the value actually set.
> > > +  @param Parity             The type of parity to use on this serial device. A Parity value of
> > > +                            DefaultParity will use the device's default parity value.
> > > +                            On output, the value actually set.
> > > +  @param DataBits           The number of data bits to use on the serial device. A DataBits
> > > +                            vaule of 0 will use the device's default data bit setting.
> > > +                            On output, the value actually set.
> > > +  @param StopBits           The number of stop bits to use on this serial device. A StopBits
> > > +                            value of DefaultStopBits will use the device's default number of
> > > +                            stop bits.
> > > +                            On output, the value actually set.
> > > +
> > > +  @retval RETURN_SUCCESS            The new attributes were set on the serial device.
> > > +  @retval RETURN_UNSUPPORTED        The serial device does not support this operation.
> > > +  @retval RETURN_INVALID_PARAMETER  One or more of the attributes has an unsupported value.
> > > +  @retval RETURN_DEVICE_ERROR       The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortSetAttributes (
> > > +  IN OUT UINT64              *BaudRate,
> > > +  IN OUT UINT32              *ReceiveFifoDepth,
> > > +  IN OUT UINT32              *Timeout,
> > > +  IN OUT EFI_PARITY_TYPE     *Parity,
> > > +  IN OUT UINT8               *DataBits,
> > > +  IN OUT EFI_STOP_BITS_TYPE  *StopBits
> > > +  )
> > > +{
> > > +  return RETURN_SUCCESS;
> > > +}
> > > diff --git
> > > a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.c
> > > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.c
> > > new file mode 100644
> > > index 000000000000..0ad5931be3ae
> > > --- /dev/null
> > > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerial
> > > +++ Po
> > > +++ rt
> > > +++ Li
> > > +++ bSbi.c
> > > @@ -0,0 +1,233 @@
> > > +/** @file
> > > +  Serial Port Library backed by SBI console.
> > > +
> > > +  Meant for SEC and PEI (XIP) environments.
> > > +
> > > +  Due to limitations of SBI console interface and XIP 
> > > + environments (on use of globals), this library instance does not 
> > > + implement reading  and polling the serial port. See 
> > > + PrePiDxeSerialPortLibRiscVSbi for  the full-featured variant meant for PrePi and DXE environments.
> > > +
> > > +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> > > +  SPDX-License-Identifier: BSD-2-Clause-Patent
> > > +
> > > +**/
> > > +
> > > +#include <Base.h>
> > > +#include <Library/SerialPortLib.h> #include 
> > > +<Library/BaseRiscVSbiLib.h>
> > > +
> > > +/**
> > > +  Initialize the serial device hardware.
> > > +
> > > +  If no initialization is required, then return RETURN_SUCCESS.
> > > +  If the serial device was successfully initialized, then return RETURN_SUCCESS.
> > > +  If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.
> > > +
> > > +  @retval RETURN_SUCCESS        The serial device was initialized.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortInitialize (
> > > +  VOID
> > > +  )
> > > +{
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Write data from buffer to serial device.
> > > +
> > > +  Writes NumberOfBytes data bytes from Buffer to the serial device.
> > > +  The number of bytes actually written to the serial device is returned.
> > > +  If the return value is less than NumberOfBytes, then the write operation failed.
> > > +  If Buffer is NULL, then ASSERT().
> > > +  If NumberOfBytes is zero, then return 0.
> > > +
> > > +  @param  Buffer           The pointer to the data buffer to be written.
> > > +  @param  NumberOfBytes    The number of bytes to written to the serial device.
> > > +
> > > +  @retval 0                NumberOfBytes is 0.
> > > +  @retval >0               The number of bytes written to the serial device.
> > > +                           If this value is less than NumberOfBytes, then the write operation failed.
> > > +
> > > +**/
> > > +UINTN
> > > +EFIAPI
> > > +SerialPortWrite (
> > > +  IN UINT8  *Buffer,
> > > +  IN UINTN  NumberOfBytes
> > > +  )
> > > +{
> > > +  SBI_RET  Ret;
> > > +  UINTN    Index;
> > > +
> > > +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> > > + SBI_EXT_DBCN);  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +      (Ret.Value != 0))
> > > +  {
> > > +    Ret = SbiCall (
> > > +            SBI_EXT_DBCN,
> > > +            SBI_EXT_DBCN_WRITE,
> > > +            3,
> > > +            NumberOfBytes,
> > > +            ((UINTN)Buffer),
> > > +            0
> > > +            );
> > > +    if (TranslateError (Ret.Error) != EFI_SUCCESS) {
> > > +      return 0;
> > > +    }
> > > +
> > > +    return Ret.Value;
> > > +  }
> > > +
> > > +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> > > + SBI_EXT_0_1_CONSOLE_PUTCHAR);  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> > > +      (Ret.Value != 0))
> > > +  {
> > > +    for (Index = 0; Index < NumberOfBytes; Index++) {
> > > +      SbiCall (SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, 1, Buffer[Index]);
> > > +    }
> > > +
> > > +    return Index;
> > > +  }
> > > +
> > > +  /*
> > > +   * Neither DBCN or legacy extension were present.
> > > +   */
> > > +  return NumberOfBytes;
> > > +}
> > > +
> > > +/**
> > > +  Read data from serial device and save the datas in buffer.
> > > +
> > > +  Reads NumberOfBytes data bytes from a serial device into the 
> > > + buffer specified by Buffer. The number of bytes actually read is returned.
> > > +  If the return value is less than NumberOfBytes, then the rest operation failed.
> > > +  If Buffer is NULL, then ASSERT().
> > > +  If NumberOfBytes is zero, then return 0.
> > > +
> > > +  @param  Buffer           The pointer to the data buffer to store the data read from the serial device.
> > > +  @param  NumberOfBytes    The number of bytes which will be read.
> > > +
> > > +  @retval 0                Read data failed; No data is to be read.
> > > +  @retval >0               The actual number of bytes read from serial device.
> > > +
> > > +**/
> > > +UINTN
> > > +EFIAPI
> > > +SerialPortRead (
> > > +  OUT UINT8  *Buffer,
> > > +  IN  UINTN  NumberOfBytes
> > > +  )
> > > +{
> > > +  return 0;
> > > +}
> > > +
> > > +/**
> > > +  Polls a serial device to see if there is any data waiting to be read.
> > > +
> > > +  Polls a serial device to see if there is any data waiting to be read.
> > > +  If there is data waiting to be read from the serial device, then TRUE is returned.
> > > +  If there is no data waiting to be read from the serial device, then FALSE is returned.
> > > +
> > > +  @retval TRUE             Data is waiting to be read from the serial device.
> > > +  @retval FALSE            There is no data waiting to be read from the serial device.
> > > +
> > > +**/
> > > +BOOLEAN
> > > +EFIAPI
> > > +SerialPortPoll (
> > > +  VOID
> > > +  )
> > > +{
> > > +  return FALSE;
> > > +}
> > > +
> > > +/**
> > > +  Sets the control bits on a serial device.
> > > +
> > > +  @param Control                Sets the bits of Control that are settable.
> > > +
> > > +  @retval RETURN_SUCCESS        The new control bits were set on the serial device.
> > > +  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortSetControl (
> > > +  IN UINT32  Control
> > > +  )
> > > +{
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Retrieve the status of the control bits on a serial device.
> > > +
> > > +  @param Control                A pointer to return the current control signals from the serial device.
> > > +
> > > +  @retval RETURN_SUCCESS        The control bits were read from the serial device.
> > > +  @retval RETURN_UNSUPPORTED    The serial device does not support this operation.
> > > +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortGetControl (
> > > +  OUT UINT32  *Control
> > > +  )
> > > +{
> > > +  *Control = 0;
> > > +  return RETURN_SUCCESS;
> > > +}
> > > +
> > > +/**
> > > +  Sets the baud rate, receive FIFO depth, transmit/receice time 
> > > +out, parity,
> > > +  data bits, and stop bits on a serial device.
> > > +
> > > +  @param BaudRate           The requested baud rate. A BaudRate value of 0 will use the
> > > +                            device's default interface speed.
> > > +                            On output, the value actually set.
> > > +  @param ReveiveFifoDepth   The requested depth of the FIFO on the receive side of the
> > > +                            serial interface. A ReceiveFifoDepth value of 0 will use
> > > +                            the device's default FIFO depth.
> > > +                            On output, the value actually set.
> > > +  @param Timeout            The requested time out for a single character in microseconds.
> > > +                            This timeout applies to both the transmit and receive side of the
> > > +                            interface. A Timeout value of 0 will use the device's default time
> > > +                            out value.
> > > +                            On output, the value actually set.
> > > +  @param Parity             The type of parity to use on this serial device. A Parity value of
> > > +                            DefaultParity will use the device's default parity value.
> > > +                            On output, the value actually set.
> > > +  @param DataBits           The number of data bits to use on the serial device. A DataBits
> > > +                            vaule of 0 will use the device's default data bit setting.
> > > +                            On output, the value actually set.
> > > +  @param StopBits           The number of stop bits to use on this serial device. A StopBits
> > > +                            value of DefaultStopBits will use the device's default number of
> > > +                            stop bits.
> > > +                            On output, the value actually set.
> > > +
> > > +  @retval RETURN_SUCCESS            The new attributes were set on the serial device.
> > > +  @retval RETURN_UNSUPPORTED        The serial device does not support this operation.
> > > +  @retval RETURN_INVALID_PARAMETER  One or more of the attributes has an unsupported value.
> > > +  @retval RETURN_DEVICE_ERROR       The serial device is not functioning correctly.
> > > +
> > > +**/
> > > +RETURN_STATUS
> > > +EFIAPI
> > > +SerialPortSetAttributes (
> > > +  IN OUT UINT64              *BaudRate,
> > > +  IN OUT UINT32              *ReceiveFifoDepth,
> > > +  IN OUT UINT32              *Timeout,
> > > +  IN OUT EFI_PARITY_TYPE     *Parity,
> > > +  IN OUT UINT8               *DataBits,
> > > +  IN OUT EFI_STOP_BITS_TYPE  *StopBits
> > > +  )
> > > +{
> > > +  return RETURN_SUCCESS;
> > > +}
> > > diff --git
> > > a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.uni
> > > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerial
> > > Po
> > > rt
> > > LibSbi.uni
> > > new file mode 100644
> > > index 000000000000..7b22caa5a090
> > > --- /dev/null
> > > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSe
> > > +++ ri
> > > +++ al
> > > +++ Po
> > > +++ rtLibSbi.uni
> > > @@ -0,0 +1,16 @@
> > > +// /** @file
> > > +// Serial Port Library backed by SBI console.
> > > +//
> > > +// Serial Port Library backed by SBI console.
> > > +//
> > > +// Copyright (c) 2023, Intel Corporation. All rights 
> > > +reserved.<BR> // // SPDX-License-Identifier: BSD-2-Clause-Patent 
> > > +// // **/
> > > +
> > > +
> > > +#string STR_MODULE_ABSTRACT             #language en-US "Serial Port Library backed by SBI console"
> > > +
> > > +#string STR_MODULE_DESCRIPTION          #language en-US "Serial Port Library backed by SBI console."
> > > +
> > > diff --git
> > > a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.uni
> > > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPort
> > > Li
> > > bS
> > > bi.uni
> > > new file mode 100644
> > > index 000000000000..7b22caa5a090
> > > --- /dev/null
> > > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerial
> > > +++ Po
> > > +++ rt
> > > +++ LibSbi.uni
> > > @@ -0,0 +1,16 @@
> > > +// /** @file
> > > +// Serial Port Library backed by SBI console.
> > > +//
> > > +// Serial Port Library backed by SBI console.
> > > +//
> > > +// Copyright (c) 2023, Intel Corporation. All rights 
> > > +reserved.<BR> // // SPDX-License-Identifier: BSD-2-Clause-Patent 
> > > +// // **/
> > > +
> > > +
> > > +#string STR_MODULE_ABSTRACT             #language en-US "Serial Port Library backed by SBI console"
> > > +
> > > +#string STR_MODULE_DESCRIPTION          #language en-US "Serial Port Library backed by SBI console."
> > > +
> > > --
> > > 2.25.1