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

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

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/SecPeiRiscVSerialPortLi
> > + bS
> > + bi
> > + .inf
> > + MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPo
> > + rt
> > + Li
> > + bSbi.inf
> >
> >  [BuildOptions]
> > diff --git
> > a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.inf
> > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.inf
> > new file mode 100644
> > index 000000000000..1d8544756bb9
> > --- /dev/null
> > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSeri
> > +++ 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/SecPeiRiscVSerialPortLi
> > bS
> > bi.inf
> > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLi
> > bS
> > bi.inf
> > new file mode 100644
> > index 000000000000..7bc7cd47c11c
> > --- /dev/null
> > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPo
> > +++ 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/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.c
> > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.c
> > new file mode 100644
> > index 000000000000..058a6573ef2d
> > --- /dev/null
> > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSeri
> > +++ 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/SecPeiRiscVSerialPortLi
> > bS
> > bi.c
> > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLi
> > bS
> > bi.c
> > new file mode 100644
> > index 000000000000..0ad5931be3ae
> > --- /dev/null
> > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPo
> > +++ 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/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.uni
> > b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPo
> > rt
> > LibSbi.uni
> > new file mode 100644
> > index 000000000000..7b22caa5a090
> > --- /dev/null
> > +++ b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSeri
> > +++ 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/SecPeiRiscVSerialPortLi
> > bS
> > bi.uni
> > b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLi
> > bS
> > bi.uni
> > new file mode 100644
> > index 000000000000..7b22caa5a090
> > --- /dev/null
> > +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPo
> > +++ 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