Silicon/RK3588: Add option to change serial baud rate within UEFI

Firstly, split up the Dw8250 serial lib into "full" and "debug"
versions. The full version is only used at SEC phase (PrePi) for setting
the specified baud rate, while the debug one is used everywhere else and
cannot reinitialize the UART.

To read the baud rate NV variable in SEC, introduce BaseVariableLib,
which is just a slightly modified FaultTolerantWritePei + VariablePei to
not use HOBs and PPIs, since they're not available this early.

Previous boot stages (DDR, TF-A, U-Boot SPL) are still hardcoded to
output at 1.5 Mbaud.

Signed-off-by: Mario Bălănică <[email protected]>

edk2-rockchip/Silicon/Rockchip/Include/Library/BaseVariableLib.h

@@ -0,0 +1,90 @@
+/** @file
+ *
+ *  Read-only non-volatile variable service library for early SEC phase.
+ *  Based on FaultTolerantWritePei and VariablePei, without using any HOBs.
+ *
+ *  Copyright (c) 2024, Mario Bălănică <[email protected]>
+ *  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
+ *  Copyright (c) Microsoft Corporation.<BR>
+ *
+ *  SPDX-License-Identifier: BSD-2-Clause-Patent
+ *
+ **/
+
+#ifndef __BASE_VARIABLE_LIB_H__
+#define __BASE_VARIABLE_LIB_H__
+
+#include <Uefi.h>
+
+/**
+  This service retrieves a variable's value using its name and GUID.
+
+  Read the specified variable from the UEFI variable store. If the Data
+  buffer is too small to hold the contents of the variable, the error
+  EFI_BUFFER_TOO_SMALL is returned and DataSize is set to the required buffer
+  size to obtain the data.
+
+  @param  VariableName          A pointer to a null-terminated string that is the variable's name.
+  @param  VariableGuid          A pointer to an EFI_GUID that is the variable's GUID. The combination of
+                                VariableGuid and VariableName must be unique.
+  @param  Attributes            If non-NULL, on return, points to the variable's attributes.
+  @param  DataSize              On entry, points to the size in bytes of the Data buffer.
+                                On return, points to the size of the data returned in Data.
+  @param  Data                  Points to the buffer which will hold the returned variable value.
+                                May be NULL with a zero DataSize in order to determine the size of the buffer needed.
+
+  @retval EFI_SUCCESS           The variable was read successfully.
+  @retval EFI_NOT_FOUND         The variable was not found.
+  @retval EFI_BUFFER_TOO_SMALL  The DataSize is too small for the resulting data.
+                                DataSize is updated with the size required for
+                                the specified variable.
+  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid, DataSize or Data is NULL.
+  @retval EFI_DEVICE_ERROR      The variable could not be retrieved because of a device error.
+
+**/
+EFI_STATUS
+EFIAPI
+BaseGetVariable (
+  IN CONST  CHAR16    *VariableName,
+  IN CONST  EFI_GUID  *VariableGuid,
+  OUT       UINT32    *Attributes,
+  IN OUT    UINTN     *DataSize,
+  OUT       VOID      *Data OPTIONAL
+  );
+
+/**
+  Return the next variable name and GUID.
+
+  This function is called multiple times to retrieve the VariableName
+  and VariableGuid of all variables currently available in the system.
+  On each call, the previous results are passed into the interface,
+  and, on return, the interface returns the data for the next
+  interface. When the entire variable list has been returned,
+  EFI_NOT_FOUND is returned.
+
+  @param  VariableNameSize  On entry, points to the size of the buffer pointed to by VariableName.
+  @param  VariableName      On entry, a pointer to a null-terminated string that is the variable's name.
+                            On return, points to the next variable's null-terminated name string.
+
+  @param  VariableGuid      On entry, a pointer to an UEFI _GUID that is the variable's GUID.
+                            On return, a pointer to the next variable's GUID.
+
+  @retval EFI_SUCCESS           The variable was read successfully.
+  @retval EFI_NOT_FOUND         The variable could not be found.
+  @retval EFI_BUFFER_TOO_SMALL  The VariableNameSize is too small for the resulting
+                                data. VariableNameSize is updated with the size
+                                required for the specified variable.
+  @retval EFI_INVALID_PARAMETER VariableName, VariableGuid or
+                                VariableNameSize is NULL.
+  @retval EFI_DEVICE_ERROR      The variable could not be retrieved because of a device error.
+
+**/
+EFI_STATUS
+EFIAPI
+BaseGetNextVariableName (
+  IN OUT UINTN     *VariableNameSize,
+  IN OUT CHAR16    *VariableName,
+  IN OUT EFI_GUID  *VariableGuid
+  );
+
+#endif // __BASE_VARIABLE_LIB_H__