diff options
| author | Laszlo Ersek <lersek@redhat.com> | 2023-10-08 17:39:09 +0200 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2023-10-26 18:55:43 +0000 |
| commit | b7e6d979732f1cf127ffd8ef4e366cf37e43fa37 (patch) | |
| tree | df4ec0fe8c5ca5455db8e60448d1bbe190d39bd8 /ArmVirtPkg | |
| parent | 115b59d9c60fffb22eeab2ed467b888e4b24c1dc (diff) | |
| download | edk2-b7e6d979732f1cf127ffd8ef4e366cf37e43fa37.tar.gz edk2-b7e6d979732f1cf127ffd8ef4e366cf37e43fa37.tar.bz2 edk2-b7e6d979732f1cf127ffd8ef4e366cf37e43fa37.zip | |
ArmVirtPkg: introduce DebugLibFdtPL011Uart Flash instance
Introduce three new DebugLib instances, forked from
MdePkg/Library/BaseDebugLibSerialPort. All three instances rely on
PL011UartLib rather than SerialPortLib so that they can customize the
PL011 UART that the debug messages are written to. All three instances
direct the debug output to the first such PL011 UART that *differs* from
the one specified in the Device Tree's /chosen node's "stdout-path"
property.
From these, DebugLibFdtPL011UartFlash mirrors EarlyFdtPL011SerialPortLib:
it parses the initial Device Tree, and initializes the UART -- a UART
different from EarlyFdtPL011SerialPortLib's -- for every message written.
Suitable for SEC, PEI_CORE, PEIM.
(Note that OVMF uses a similar set of dedicated DebugLib instances
(PlatformDebugLibIoPort) for logging to the (x86-only) isa-debugcon device
from various firmware phases.)
The contexts in which these DebugLib instances run are identical to those
in which the corresponding SerialPortLib instances run. The particular
original dependency chain is
BaseDebugLibSerialPort (SEC, PEI_CORE, PEIM)
EarlyFdtPL011SerialPortLib
PcdDeviceTreeInitialBaseAddress
FdtSerialPortAddressLib
PL011UartLib
and the new dependency chain is
DebugLibFdtPL011UartFlash (SEC, PEI_CORE, PEIM)
PcdDeviceTreeInitialBaseAddress
FdtSerialPortAddressLib
PL011UartLib
Note that EarlyFdtPL011SerialPortLib remains in use (just not via
BaseDebugLibSerialPort), namely for direct SerialPortLib calls from SEC,
PEI_CORE, PEIM. See for example commit 56035d1c8b25
("ArmPlatformPkg/PrePeiCore: Print the firmware version early in boot",
2022-10-25).
The ArmVirtPkg DSC files will be switched to the new library instances in
a separate patch.
This patch is worth viewing with "git show --find-copies-harder".
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20231008153912.175941-7-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=4577
[lersek@redhat.com: add TianoCore BZ reference]
Diffstat (limited to 'ArmVirtPkg')
4 files changed, 555 insertions, 0 deletions
diff --git a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLib.c b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLib.c new file mode 100644 index 0000000000..0da84ba8d2 --- /dev/null +++ b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLib.c @@ -0,0 +1,355 @@ +/** @file
+ Originally copied from "MdePkg/Library/BaseDebugLibSerialPort/DebugLib.c" at
+ commit f36e1ec1f0a5, and customized for:
+
+ - RAM vs. flash dependent PL011 UART initialization,
+
+ - direct PL011 UART access, with the base address taken from the device tree
+ such that the debug output be separate from the SerialPortLib / UEFI console
+ traffic.
+
+ Both of these customizations are hidden behind DebugLibFdtPL011UartWrite(),
+ which replaces SerialPortWrite().
+
+ Copyright (C) Red Hat
+ Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Base.h>
+#include <Library/DebugLib.h>
+#include <Library/BaseLib.h>
+#include <Library/PrintLib.h>
+#include <Library/PcdLib.h>
+#include <Library/BaseMemoryLib.h>
+#include <Library/DebugPrintErrorLevelLib.h>
+
+#include "Write.h"
+
+//
+// Define the maximum debug and assert message length that this library supports
+//
+#define MAX_DEBUG_MESSAGE_LENGTH 0x100
+
+//
+// VA_LIST can not initialize to NULL for all compiler, so we use this to
+// indicate a null VA_LIST
+//
+VA_LIST mVaListNull;
+
+/**
+ Prints a debug message to the debug output device if the specified error level is enabled.
+
+ If any bit in ErrorLevel is also set in DebugPrintErrorLevelLib function
+ GetDebugPrintErrorLevel (), then print the message specified by Format and the
+ associated variable argument list to the debug output device.
+
+ If Format is NULL, then ASSERT().
+
+ @param ErrorLevel The error level of the debug message.
+ @param Format Format string for the debug message to print.
+ @param ... Variable argument list whose contents are accessed
+ based on the format string specified by Format.
+
+**/
+VOID
+EFIAPI
+DebugPrint (
+ IN UINTN ErrorLevel,
+ IN CONST CHAR8 *Format,
+ ...
+ )
+{
+ VA_LIST Marker;
+
+ VA_START (Marker, Format);
+ DebugVPrint (ErrorLevel, Format, Marker);
+ VA_END (Marker);
+}
+
+/**
+ Prints a debug message to the debug output device if the specified
+ error level is enabled base on Null-terminated format string and a
+ VA_LIST argument list or a BASE_LIST argument list.
+
+ If any bit in ErrorLevel is also set in DebugPrintErrorLevelLib function
+ GetDebugPrintErrorLevel (), then print the message specified by Format and
+ the associated variable argument list to the debug output device.
+
+ If Format is NULL, then ASSERT().
+
+ @param ErrorLevel The error level of the debug message.
+ @param Format Format string for the debug message to print.
+ @param VaListMarker VA_LIST marker for the variable argument list.
+ @param BaseListMarker BASE_LIST marker for the variable argument list.
+
+**/
+VOID
+DebugPrintMarker (
+ IN UINTN ErrorLevel,
+ IN CONST CHAR8 *Format,
+ IN VA_LIST VaListMarker,
+ IN BASE_LIST BaseListMarker
+ )
+{
+ CHAR8 Buffer[MAX_DEBUG_MESSAGE_LENGTH];
+
+ //
+ // If Format is NULL, then ASSERT().
+ //
+ ASSERT (Format != NULL);
+
+ //
+ // Check driver debug mask value and global mask
+ //
+ if ((ErrorLevel & GetDebugPrintErrorLevel ()) == 0) {
+ return;
+ }
+
+ //
+ // Convert the DEBUG() message to an ASCII String
+ //
+ if (BaseListMarker == NULL) {
+ AsciiVSPrint (Buffer, sizeof (Buffer), Format, VaListMarker);
+ } else {
+ AsciiBSPrint (Buffer, sizeof (Buffer), Format, BaseListMarker);
+ }
+
+ //
+ // Send the print string to a Serial Port
+ //
+ DebugLibFdtPL011UartWrite ((UINT8 *)Buffer, AsciiStrLen (Buffer));
+}
+
+/**
+ Prints a debug message to the debug output device if the specified
+ error level is enabled.
+
+ If any bit in ErrorLevel is also set in DebugPrintErrorLevelLib function
+ GetDebugPrintErrorLevel (), then print the message specified by Format and
+ the associated variable argument list to the debug output device.
+
+ If Format is NULL, then ASSERT().
+
+ @param ErrorLevel The error level of the debug message.
+ @param Format Format string for the debug message to print.
+ @param VaListMarker VA_LIST marker for the variable argument list.
+
+**/
+VOID
+EFIAPI
+DebugVPrint (
+ IN UINTN ErrorLevel,
+ IN CONST CHAR8 *Format,
+ IN VA_LIST VaListMarker
+ )
+{
+ DebugPrintMarker (ErrorLevel, Format, VaListMarker, NULL);
+}
+
+/**
+ Prints a debug message to the debug output device if the specified
+ error level is enabled.
+ This function use BASE_LIST which would provide a more compatible
+ service than VA_LIST.
+
+ If any bit in ErrorLevel is also set in DebugPrintErrorLevelLib function
+ GetDebugPrintErrorLevel (), then print the message specified by Format and
+ the associated variable argument list to the debug output device.
+
+ If Format is NULL, then ASSERT().
+
+ @param ErrorLevel The error level of the debug message.
+ @param Format Format string for the debug message to print.
+ @param BaseListMarker BASE_LIST marker for the variable argument list.
+
+**/
+VOID
+EFIAPI
+DebugBPrint (
+ IN UINTN ErrorLevel,
+ IN CONST CHAR8 *Format,
+ IN BASE_LIST BaseListMarker
+ )
+{
+ DebugPrintMarker (ErrorLevel, Format, mVaListNull, BaseListMarker);
+}
+
+/**
+ Prints an assert message containing a filename, line number, and description.
+ This may be followed by a breakpoint or a dead loop.
+
+ Print a message of the form "ASSERT <FileName>(<LineNumber>): <Description>\n"
+ to the debug output device. If DEBUG_PROPERTY_ASSERT_BREAKPOINT_ENABLED bit of
+ PcdDebugProperyMask is set then CpuBreakpoint() is called. Otherwise, if
+ DEBUG_PROPERTY_ASSERT_DEADLOOP_ENABLED bit of PcdDebugProperyMask is set then
+ CpuDeadLoop() is called. If neither of these bits are set, then this function
+ returns immediately after the message is printed to the debug output device.
+ DebugAssert() must actively prevent recursion. If DebugAssert() is called while
+ processing another DebugAssert(), then DebugAssert() must return immediately.
+
+ If FileName is NULL, then a <FileName> string of "(NULL) Filename" is printed.
+ If Description is NULL, then a <Description> string of "(NULL) Description" is printed.
+
+ @param FileName The pointer to the name of the source file that generated the assert condition.
+ @param LineNumber The line number in the source file that generated the assert condition
+ @param Description The pointer to the description of the assert condition.
+
+**/
+VOID
+EFIAPI
+DebugAssert (
+ IN CONST CHAR8 *FileName,
+ IN UINTN LineNumber,
+ IN CONST CHAR8 *Description
+ )
+{
+ CHAR8 Buffer[MAX_DEBUG_MESSAGE_LENGTH];
+
+ //
+ // Generate the ASSERT() message in Ascii format
+ //
+ AsciiSPrint (Buffer, sizeof (Buffer), "ASSERT [%a] %a(%d): %a\n", gEfiCallerBaseName, FileName, LineNumber, Description);
+
+ //
+ // Send the print string to the Console Output device
+ //
+ DebugLibFdtPL011UartWrite ((UINT8 *)Buffer, AsciiStrLen (Buffer));
+
+ //
+ // Generate a Breakpoint, DeadLoop, or NOP based on PCD settings
+ //
+ if ((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_ASSERT_BREAKPOINT_ENABLED) != 0) {
+ CpuBreakpoint ();
+ } else if ((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_ASSERT_DEADLOOP_ENABLED) != 0) {
+ CpuDeadLoop ();
+ }
+}
+
+/**
+ Fills a target buffer with PcdDebugClearMemoryValue, and returns the target buffer.
+
+ This function fills Length bytes of Buffer with the value specified by
+ PcdDebugClearMemoryValue, and returns Buffer.
+
+ If Buffer is NULL, then ASSERT().
+ If Length is greater than (MAX_ADDRESS - Buffer + 1), then ASSERT().
+
+ @param Buffer The pointer to the target buffer to be filled with PcdDebugClearMemoryValue.
+ @param Length The number of bytes in Buffer to fill with zeros PcdDebugClearMemoryValue.
+
+ @return Buffer The pointer to the target buffer filled with PcdDebugClearMemoryValue.
+
+**/
+VOID *
+EFIAPI
+DebugClearMemory (
+ OUT VOID *Buffer,
+ IN UINTN Length
+ )
+{
+ //
+ // If Buffer is NULL, then ASSERT().
+ //
+ ASSERT (Buffer != NULL);
+
+ //
+ // SetMem() checks for the the ASSERT() condition on Length and returns Buffer
+ //
+ return SetMem (Buffer, Length, PcdGet8 (PcdDebugClearMemoryValue));
+}
+
+/**
+ Returns TRUE if ASSERT() macros are enabled.
+
+ This function returns TRUE if the DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED bit of
+ PcdDebugProperyMask is set. Otherwise FALSE is returned.
+
+ @retval TRUE The DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED bit of PcdDebugProperyMask is set.
+ @retval FALSE The DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED bit of PcdDebugProperyMask is clear.
+
+**/
+BOOLEAN
+EFIAPI
+DebugAssertEnabled (
+ VOID
+ )
+{
+ return (BOOLEAN)((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_DEBUG_ASSERT_ENABLED) != 0);
+}
+
+/**
+ Returns TRUE if DEBUG() macros are enabled.
+
+ This function returns TRUE if the DEBUG_PROPERTY_DEBUG_PRINT_ENABLED bit of
+ PcdDebugProperyMask is set. Otherwise FALSE is returned.
+
+ @retval TRUE The DEBUG_PROPERTY_DEBUG_PRINT_ENABLED bit of PcdDebugProperyMask is set.
+ @retval FALSE The DEBUG_PROPERTY_DEBUG_PRINT_ENABLED bit of PcdDebugProperyMask is clear.
+
+**/
+BOOLEAN
+EFIAPI
+DebugPrintEnabled (
+ VOID
+ )
+{
+ return (BOOLEAN)((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_DEBUG_PRINT_ENABLED) != 0);
+}
+
+/**
+ Returns TRUE if DEBUG_CODE() macros are enabled.
+
+ This function returns TRUE if the DEBUG_PROPERTY_DEBUG_CODE_ENABLED bit of
+ PcdDebugProperyMask is set. Otherwise FALSE is returned.
+
+ @retval TRUE The DEBUG_PROPERTY_DEBUG_CODE_ENABLED bit of PcdDebugProperyMask is set.
+ @retval FALSE The DEBUG_PROPERTY_DEBUG_CODE_ENABLED bit of PcdDebugProperyMask is clear.
+
+**/
+BOOLEAN
+EFIAPI
+DebugCodeEnabled (
+ VOID
+ )
+{
+ return (BOOLEAN)((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_DEBUG_CODE_ENABLED) != 0);
+}
+
+/**
+ Returns TRUE if DEBUG_CLEAR_MEMORY() macro is enabled.
+
+ This function returns TRUE if the DEBUG_PROPERTY_CLEAR_MEMORY_ENABLED bit of
+ PcdDebugProperyMask is set. Otherwise FALSE is returned.
+
+ @retval TRUE The DEBUG_PROPERTY_CLEAR_MEMORY_ENABLED bit of PcdDebugProperyMask is set.
+ @retval FALSE The DEBUG_PROPERTY_CLEAR_MEMORY_ENABLED bit of PcdDebugProperyMask is clear.
+
+**/
+BOOLEAN
+EFIAPI
+DebugClearMemoryEnabled (
+ VOID
+ )
+{
+ return (BOOLEAN)((PcdGet8 (PcdDebugPropertyMask) & DEBUG_PROPERTY_CLEAR_MEMORY_ENABLED) != 0);
+}
+
+/**
+ Returns TRUE if any one of the bit is set both in ErrorLevel and PcdFixedDebugPrintErrorLevel.
+
+ This function compares the bit mask of ErrorLevel and PcdFixedDebugPrintErrorLevel.
+
+ @retval TRUE Current ErrorLevel is supported.
+ @retval FALSE Current ErrorLevel is not supported.
+
+**/
+BOOLEAN
+EFIAPI
+DebugPrintLevelEnabled (
+ IN CONST UINTN ErrorLevel
+ )
+{
+ return (BOOLEAN)((ErrorLevel & PcdGet32 (PcdFixedDebugPrintErrorLevel)) != 0);
+}
diff --git a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLibFdtPL011UartFlash.inf b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLibFdtPL011UartFlash.inf new file mode 100644 index 0000000000..7870ca2ae4 --- /dev/null +++ b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/DebugLibFdtPL011UartFlash.inf @@ -0,0 +1,54 @@ +## @file
+# DebugLib instance that produces debug output directly via PL011UartLib.
+#
+# If there are at least two PL011 UARTs in the device tree, and the /chosen
+# node's "stdout-path" property references one PL011 UART, then both raw
+# SerialPortLib IO, and -- via SerialDxe -- UEFI console IO, will occur on that
+# UART; and this DebugLib instance will produce output on a *different* UART.
+#
+# This instance is suitable for modules that may run from flash or RAM.
+#
+# Copyright (C) Red Hat
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+
+[Defines]
+ INF_VERSION = 1.27
+ BASE_NAME = DebugLibFdtPL011UartFlash
+ FILE_GUID = 43A4C56B-D071-4CE0-A157-9D59E6161DEC
+ MODULE_TYPE = BASE
+ VERSION_STRING = 1.0
+ LIBRARY_CLASS = DebugLib|SEC PEI_CORE PEIM
+
+[Sources]
+ DebugLib.c
+ Flash.c
+ Write.h
+
+[Packages]
+ ArmPlatformPkg/ArmPlatformPkg.dec
+ ArmVirtPkg/ArmVirtPkg.dec
+ MdePkg/MdePkg.dec
+
+[LibraryClasses]
+ BaseLib
+ BaseMemoryLib
+ DebugPrintErrorLevelLib
+ FdtSerialPortAddressLib # Flash.c
+ PL011UartLib
+ PcdLib
+ PrintLib
+
+[Pcd]
+ gArmVirtTokenSpaceGuid.PcdDeviceTreeInitialBaseAddress # Flash.c
+ gEfiMdePkgTokenSpaceGuid.PcdDebugClearMemoryValue
+ gEfiMdePkgTokenSpaceGuid.PcdDebugPropertyMask
+ gEfiMdePkgTokenSpaceGuid.PcdFixedDebugPrintErrorLevel
+
+[FixedPcd]
+ gArmPlatformTokenSpaceGuid.PL011UartClkInHz
+ gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate
+ gEfiMdePkgTokenSpaceGuid.PcdUartDefaultDataBits
+ gEfiMdePkgTokenSpaceGuid.PcdUartDefaultParity
+ gEfiMdePkgTokenSpaceGuid.PcdUartDefaultStopBits
diff --git a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Flash.c b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Flash.c new file mode 100644 index 0000000000..a624e0860d --- /dev/null +++ b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Flash.c @@ -0,0 +1,107 @@ +/** @file
+ Define DebugLibFdtPL011UartWrite() for modules that may run from flash or RAM.
+
+ Copyright (C) Red Hat
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Library/FdtSerialPortAddressLib.h>
+#include <Library/PL011UartLib.h>
+#include <Library/PcdLib.h>
+
+#include "Write.h"
+
+/**
+ (Copied from SerialPortWrite() in "MdePkg/Include/Library/SerialPortLib.h" at
+ commit c4547aefb3d0, with the Buffer non-nullity assertion removed:)
+
+ 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 NumberOfBytes is zero, then return 0.
+
+ @param Buffer Pointer to the data buffer to be written.
+ @param NumberOfBytes 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
+DebugLibFdtPL011UartWrite (
+ IN UINT8 *Buffer,
+ IN UINTN NumberOfBytes
+ )
+{
+ CONST VOID *DeviceTree;
+ RETURN_STATUS Status;
+ FDT_SERIAL_PORTS Ports;
+ UINT64 DebugAddress;
+ UINT64 BaudRate;
+ UINT32 ReceiveFifoDepth;
+ EFI_PARITY_TYPE Parity;
+ UINT8 DataBits;
+ EFI_STOP_BITS_TYPE StopBits;
+
+ DeviceTree = (VOID *)(UINTN)PcdGet64 (PcdDeviceTreeInitialBaseAddress);
+ if (DeviceTree == NULL) {
+ return 0;
+ }
+
+ Status = FdtSerialGetPorts (DeviceTree, "arm,pl011", &Ports);
+ if (RETURN_ERROR (Status)) {
+ return 0;
+ }
+
+ if (Ports.NumberOfPorts == 1) {
+ //
+ // Just one UART; direct DebugLib to it.
+ //
+ DebugAddress = Ports.BaseAddress[0];
+ } else {
+ UINT64 ConsoleAddress;
+
+ Status = FdtSerialGetConsolePort (DeviceTree, &ConsoleAddress);
+ if (EFI_ERROR (Status)) {
+ //
+ // At least two UARTs; but failed to get the console preference. Use the
+ // second UART for DebugLib.
+ //
+ DebugAddress = Ports.BaseAddress[1];
+ } else {
+ //
+ // At least two UARTs; and console preference available. Use the first
+ // such UART for DebugLib that *differs* from ConsoleAddress.
+ //
+ if (ConsoleAddress == Ports.BaseAddress[0]) {
+ DebugAddress = Ports.BaseAddress[1];
+ } else {
+ DebugAddress = Ports.BaseAddress[0];
+ }
+ }
+ }
+
+ BaudRate = (UINTN)FixedPcdGet64 (PcdUartDefaultBaudRate);
+ ReceiveFifoDepth = 0; // Use the default value for Fifo depth
+ Parity = (EFI_PARITY_TYPE)FixedPcdGet8 (PcdUartDefaultParity);
+ DataBits = FixedPcdGet8 (PcdUartDefaultDataBits);
+ StopBits = (EFI_STOP_BITS_TYPE)FixedPcdGet8 (PcdUartDefaultStopBits);
+
+ Status = PL011UartInitializePort (
+ (UINTN)DebugAddress,
+ FixedPcdGet32 (PL011UartClkInHz),
+ &BaudRate,
+ &ReceiveFifoDepth,
+ &Parity,
+ &DataBits,
+ &StopBits
+ );
+ if (RETURN_ERROR (Status)) {
+ return 0;
+ }
+
+ return PL011UartWrite ((UINTN)DebugAddress, Buffer, NumberOfBytes);
+}
diff --git a/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Write.h b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Write.h new file mode 100644 index 0000000000..2cf6106764 --- /dev/null +++ b/ArmVirtPkg/Library/DebugLibFdtPL011Uart/Write.h @@ -0,0 +1,39 @@ +/** @file
+ Declare DebugLibFdtPL011UartWrite(), for abstracting PL011 UART initialization
+ differences between flash- vs. RAM-based modules.
+
+ Copyright (C) Red Hat
+ Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
+ Copyright (c) 2012 - 2014, ARM Ltd. All rights reserved.
+
+ SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef DEBUG_LIB_FDT_PL011_UART_WRITE_H_
+#define DEBUG_LIB_FDT_PL011_UART_WRITE_H_
+
+/**
+ (Copied from SerialPortWrite() in "MdePkg/Include/Library/SerialPortLib.h" at
+ commit c4547aefb3d0, with the Buffer non-nullity assertion removed:)
+
+ 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 NumberOfBytes is zero, then return 0.
+
+ @param Buffer Pointer to the data buffer to be written.
+ @param NumberOfBytes 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
+DebugLibFdtPL011UartWrite (
+ IN UINT8 *Buffer,
+ IN UINTN NumberOfBytes
+ );
+
+#endif
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