[edk2-devel] [edk2-platforms][PATCH V6 01/16] Platform/Loongson: Add Serial Port library

xianglai lixianglai at loongson.cn
Thu Nov 17 02:39:27 UTC 2022


Serial Port library for LoongarchQemuPkg

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4054

Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Bibo Mao <maobibo at loongson.cn>
Cc: Chao Li <lichao at loongson.cn>
Cc: Leif Lindholm <quic_llindhol at quicinc.com>
Cc: Liming Gao <gaoliming at byosoft.com.cn>
Cc: Michael D Kinney <michael.d.kinney at intel.com>
Signed-off-by: xianglai li <lixianglai at loongson.cn>
Reviewed-by: Chao Li <lichao at loongson.cn>
---
 .../Include/Guid/Early16550UartBaseAddress.h  |  22 +
 .../LoongArchQemuPkg/Include/Library/Cpu.h    | 237 +++++
 .../Fdt16550SerialPortHookLib.c               |  57 ++
 .../Fdt16550SerialPortHookLib.inf             |  38 +
 .../SerialPortLib/EarlySerialPortLib16550.c   | 900 ++++++++++++++++++
 .../SerialPortLib/EarlySerialPortLib16550.inf |  46 +
 6 files changed, 1300 insertions(+)
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Include/Guid/Early16550UartBaseAddress.h
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Include/Library/Cpu.h
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.c
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.inf
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.c
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.inf

diff --git a/Platform/Loongson/LoongArchQemuPkg/Include/Guid/Early16550UartBaseAddress.h b/Platform/Loongson/LoongArchQemuPkg/Include/Guid/Early16550UartBaseAddress.h
new file mode 100644
index 0000000000..95aa8f4bc0
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Include/Guid/Early16550UartBaseAddress.h
@@ -0,0 +1,22 @@
+/** @file
+  GUID for the HOB that caches the base address of the 16550 serial port, for
+  when PCD access is not available.
+
+  Copyright (c) 2022 Loongson Technology Corporation Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef EARLY_16550_UART_BASE_ADDRESS_H__
+#define EARLY_16550_UART_BASE_ADDRESS_H__
+
+#define EARLY_16550_UART_BASE_ADDRESS_GUID  {      \
+  0xea67ca3e, 0x1f54, 0x436b, {                    \
+    0x97, 0x88, 0xd4, 0xeb, 0x29, 0xc3, 0x42, 0x67 \
+    }                                              \
+  }
+
+extern EFI_GUID  gEarly16550UartBaseAddressGuid;
+
+#endif // EARLY_16550_UART_BASE_ADDRESS_H__
diff --git a/Platform/Loongson/LoongArchQemuPkg/Include/Library/Cpu.h b/Platform/Loongson/LoongArchQemuPkg/Include/Library/Cpu.h
new file mode 100644
index 0000000000..c6599c6ed7
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Include/Library/Cpu.h
@@ -0,0 +1,237 @@
+/** @file
+
+  Copyright (c) 2022 Loongson Technology Corporation Limited. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+  @par Glossary:
+    - EXC     - Exception
+    - INT     - Interrupt
+    - FPU     - Floating Point Unit
+    - CSR     - CPU Status Register
+    - READQ   - Read Quad Word
+**/
+#ifndef LOONGARCH_CPU_H_
+#define LOONGARCH_CPU_H_
+
+/* Exception types decoded by machdep exception decoder */
+#define EXC_INT                     0       /* HW interrupt */
+#define EXC_TLBL                    1       /* TLB miss on a load */
+#define EXC_TLBS                    2       /* TLB miss on a store */
+#define EXC_TLBI                    3       /* TLB miss on a ifetch */
+#define EXC_TLBM                    4       /* TLB modified fault */
+#define EXC_TLBRI                   5       /* TLB Read-Inhibit exception */
+#define EXC_TLBXI                   6       /* TLB Execution-Inhibit exception */
+#define EXC_TLBPE                   7       /* TLB Privilege Error */
+#define EXC_ADE                     8       /* Address Error */
+#define EXC_ALE                     9       /* Unalign Access */
+#define EXC_OOB                     10      /* Out of bounds */
+#define EXC_SYS                     11      /* System call */
+#define EXC_BP                      12      /* Breakpoint */
+#define EXC_INE                     13      /* Inst. Not Exist */
+#define EXC_IPE                     14      /* Inst. Privileged Error */
+#define EXC_FPDIS                   15      /* FPU Disabled */
+#define EXC_LSXDIS                  16      /* LSX Disabled */
+#define EXC_LASXDIS                 17      /* LASX Disabled */
+#define EXC_FPE                     18      /* Floating Point Exception */
+#define EXC_WATCH                   19      /* Watch address reference */
+#define EXC_BAD                     255     /* Undecodeable */
+
+#define COPY_SIGCODE    // copy sigcode above user stack in exec
+#define ZERO                        $r0 /* wired zero */
+#define RA                          $r1 /* return address */
+#define GP                          $r2 /* global pointer - caller saved for PIC */
+#define SP                          $r3 /* stack pointer */
+#define V0                          $r4 /* return value - caller saved */
+#define V1                          $r5
+#define A0                          $r4 /* argument registers */
+#define A1                          $r5
+#define A2                          $r6
+#define A3                          $r7
+#define A4                          $r8 /* arg reg 64 bit; caller saved in 32 bit */
+#define A5                          $r9
+#define A6                          $r10
+#define A7                          $r11
+#define T0                          $r12 /* caller saved */
+#define T1                          $r13
+#define T2                          $r14
+#define T3                          $r15
+#define T4                          $r16 /* callee saved */
+#define T5                          $r17
+#define T6                          $r18
+#define T7                          $r19
+#define T8                          $r20 /* caller saved */
+#define TP                          $r21 /* TLS */
+#define FP                          $r22 /* frame pointer */
+#define S0                          $r23 /* callee saved */
+#define S1                          $r24
+#define S2                          $r25
+#define S3                          $r26
+#define S4                          $r27
+#define S5                          $r28
+#define S6                          $r29
+#define S7                          $r30
+#define S8                          $r31 /* callee saved */
+
+#define FCSR0                       $r0
+
+//
+// Location of the saved registers relative to ZERO.
+// Usage is p->p_regs[XX].
+//
+#define RA_NUM                      1
+#define GP_NUM                      2
+#define SP_NUM                      3
+#define A0_NUM                      4
+#define A1_NUM                      5
+#define A2_NUM                      6
+#define A3_NUM                      7
+#define A4_NUM                      8
+#define A5_NUM                      9
+#define A6_NUM                      10
+#define A7_NUM                      11
+#define T0_NUM                      12
+#define T1_NUM                      13
+#define T2_NUM                      14
+#define T3_NUM                      15
+#define T4_NUM                      16
+#define T5_NUM                      17
+#define T6_NUM                      18
+#define T7_NUM                      19
+#define T8_NUM                      20
+#define TP_NUM                      21
+#define FP_NUM                      22
+#define S0_NUM                      23
+#define S1_NUM                      24
+#define S2_NUM                      25
+#define S3_NUM                      26
+#define S4_NUM                      27
+#define S5_NUM                      28
+#define S6_NUM                      29
+#define S7_NUM                      30
+#define S8_NUM                      31
+
+#define FP0_NUM                     0
+#define FP1_NUM                     1
+#define FP2_NUM                     2
+#define FP3_NUM                     3
+#define FP4_NUM                     4
+#define FP5_NUM                     5
+#define FP6_NUM                     6
+#define FP7_NUM                     7
+#define FP8_NUM                     8
+#define FP9_NUM                     9
+#define FP10_NUM                    10
+#define FP11_NUM                    11
+#define FP12_NUM                    12
+#define FP13_NUM                    13
+#define FP14_NUM                    14
+#define FP15_NUM                    15
+#define FP16_NUM                    16
+#define FP17_NUM                    17
+#define FP18_NUM                    18
+#define FP19_NUM                    19
+#define FP20_NUM                    20
+#define FP21_NUM                    21
+#define FP22_NUM                    22
+#define FP23_NUM                    23
+#define FP24_NUM                    24
+#define FP25_NUM                    25
+#define FP26_NUM                    26
+#define FP27_NUM                    27
+#define FP28_NUM                    28
+#define FP29_NUM                    29
+#define FP30_NUM                    30
+#define FP31_NUM                    31
+#define FCSR_NUM                    32
+#define FCC_NUM                     33
+
+#ifdef __ASSEMBLY__
+#define _ULCAST_
+#define _U64CAST_
+#else
+#define _ULCAST_ (unsigned long)
+#define _U64CAST_ (u64)
+#endif
+
+#define LOONGARCH_CSR_CRMD          0
+#define LOONGARCH_CSR_PRMD          1
+#define LOONGARCH_CSR_EUEN          2
+#define CSR_EUEN_LBTEN_SHIFT        3
+#define CSR_EUEN_LBTEN              (_ULCAST_(0x1) << CSR_EUEN_LBTEN_SHIFT)
+#define CSR_EUEN_LASXEN_SHIFT       2
+#define CSR_EUEN_LASXEN             (_ULCAST_(0x1) << CSR_EUEN_LASXEN_SHIFT)
+#define CSR_EUEN_LSXEN_SHIFT        1
+#define CSR_EUEN_LSXEN              (_ULCAST_(0x1) << CSR_EUEN_LSXEN_SHIFT)
+#define CSR_EUEN_FPEN_SHIFT         0
+#define CSR_EUEN_FPEN               (_ULCAST_(0x1) << CSR_EUEN_FPEN_SHIFT)
+#define LOONGARCH_CSR_ECFG          4
+
+/* Exception status */
+#define LOONGARCH_CSR_ESTAT         5
+#define CSR_ESTAT_ESUBCODE_SHIFT    22
+#define CSR_ESTAT_ESUBCODE_WIDTH    9
+#define CSR_ESTAT_ESUBCODE          (_ULCAST_(0x1ff) << CSR_ESTAT_ESUBCODE_SHIFT)
+#define CSR_ESTAT_EXC_SHIFT         16
+#define CSR_ESTAT_EXC_WIDTH         6
+#define CSR_ESTAT_EXC               (_ULCAST_(0x3f) << CSR_ESTAT_EXC_SHIFT)
+#define CSR_ESTAT_IS_SHIFT          0
+#define CSR_ESTAT_IS_WIDTH          15
+#define CSR_ESTAT_IS                (_ULCAST_(0x7fff) << CSR_ESTAT_IS_SHIFT)
+
+#define LOONGARCH_CSR_EPC           6
+#define LOONGARCH_CSR_BADV          7
+#define LOONGARCH_CSR_BADINST       8
+#define LOONGARCH_CSR_BADI          8
+#define LOONGARCH_CSR_EBASE         0xc     /* Exception entry base address */
+#define LOONGARCH_CSR_CPUNUM        0x20    /* CPU core number */
+
+/* register number save in stack on exception */
+#define FP_BASE_NUM                 34
+#define BASE_NUM                    32
+#define CSR_NUM                     10
+#define FP_BASE_INDEX               (CSR_NUM + BASE_NUM)
+#define BOOTCORE_ID                 0
+
+#define LOONGSON_IOCSR_IPI_STATUS   0x1000
+#define LOONGSON_IOCSR_IPI_EN       0x1004
+#define LOONGSON_IOCSR_IPI_SET      0x1008
+#define LOONGSON_IOCSR_IPI_CLEAR    0x100c
+#define LOONGSON_CSR_MAIL_BUF0      0x1020
+#define LOONGSON_CSR_MAIL_BUF1      0x1028
+#define LOONGSON_CSR_MAIL_BUF2      0x1030
+#define LOONGSON_CSR_MAIL_BUF3      0x1038
+
+/* Bit Domains for CFG registers */
+#define LOONGARCH_CPUCFG4           0x4
+#define LOONGARCH_CPUCFG5           0x5
+
+/* Kscratch registers */
+#define LOONGARCH_CSR_KS0           0x30
+#define LOONGARCH_CSR_KS1           0x31
+
+/* Stable timer registers */
+#define LOONGARCH_CSR_TMCFG         0x41
+#define LOONGARCH_CSR_TMCFG_EN      (1ULL << 0)
+#define LOONGARCH_CSR_TMCFG_PERIOD  (1ULL << 1)
+#define LOONGARCH_CSR_TMCFG_TIMEVAL (0x3fffffffffffULL << 2)
+#define LOONGARCH_CSR_TVAL          0x42    /* Timer value */
+#define LOONGARCH_CSR_CNTC          0x43    /* Timer offset */
+#define LOONGARCH_CSR_TINTCLR       0x44    /* Timer interrupt clear */
+
+/* TLB refill exception base address */
+#define LOONGARCH_CSR_TLBREBASE     0x88
+#define LOONGARCH_CSR_TLBRSAVE      0x8b    /* KScratch for TLB refill exception */
+#define LOONGARCH_CSR_PGD           0x1b    /* Page table base */
+
+/* Invalid addr with global=1 or matched asid in current tlb */
+#define INVTLB_ADDR_GTRUE_OR_ASID   0x6
+
+/* Bits 8 and 9 of FPU Status Register specify the rounding mode */
+#define FPU_CSR_RM                  0x300
+#define FPU_CSR_RN                  0x000   /* nearest */
+#define FPU_CSR_RZ                  0x100   /* towards zero */
+#define FPU_CSR_RU                  0x200   /* towards +Infinity */
+#define FPU_CSR_RD                  0x300   /* towards -Infinity */
+
+#endif
diff --git a/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.c b/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.c
new file mode 100644
index 0000000000..2b766e10dc
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.c
@@ -0,0 +1,57 @@
+/** @file
+  Platform Hook Library instance for 16550 Uart.
+
+  Copyright (c) 2022, Loongson Limited. All rights reserved.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include <Uefi.h>
+
+#include <Pi/PiBootMode.h>
+#include <Pi/PiHob.h>
+
+#include <Guid/Early16550UartBaseAddress.h>
+#include <Guid/Fdt.h>
+#include <Guid/FdtHob.h>
+
+#include <Library/BaseLib.h>
+#include <Library/HobLib.h>
+#include <Library/PcdLib.h>
+#include <Library/PlatformHookLib.h>
+
+/** Platform hook to retrieve the 16550 UART base address from the GUID Hob
+    that caches the UART base address from early boot stage and store it in
+    PcdSerialRegisterBase.
+
+  @retval RETURN_SUCCESS    Success.
+  @retval RETURN_NOT_FOUND  Serial Port information not found.
+
+**/
+RETURN_STATUS
+EFIAPI
+PlatformHookSerialPortInitialize (
+  VOID
+  )
+{
+  VOID    *Hob;
+  UINT64  *UartBase;
+
+  if (PcdGet64 (PcdSerialRegisterBase) != 0) {
+    return RETURN_SUCCESS;
+  }
+
+  Hob = GetFirstGuidHob (&gEarly16550UartBaseAddressGuid);
+  if ((Hob == NULL) || (GET_GUID_HOB_DATA_SIZE (Hob) != sizeof (*UartBase))) {
+    return RETURN_NOT_FOUND;
+  }
+
+  UartBase = GET_GUID_HOB_DATA (Hob);
+  if ((UINTN)*UartBase == 0) {
+    return RETURN_NOT_FOUND;
+  }
+
+  return (RETURN_STATUS)PcdSet64S (PcdSerialRegisterBase, (UINTN)*UartBase);
+}
diff --git a/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.inf b/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.inf
new file mode 100644
index 0000000000..cbc99864be
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Library/Fdt16550SerialPortHookLib/Fdt16550SerialPortHookLib.inf
@@ -0,0 +1,38 @@
+## @file
+#  Platform Hook Library instance for 16550 Uart.
+#
+#  Copyright (c) 2022, Loongson Limited. All rights reserved.
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x0001001B
+  BASE_NAME                      = Fdt16550SerialPortHookLib
+  MODULE_UNI_FILE                = Fdt16550SerialPortHookLib.uni
+  FILE_GUID                      = C6DFD3F0-179D-4376-89A5-F641A2E7EFB5
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.0
+  LIBRARY_CLASS                  = PlatformHookLib|DXE_CORE DXE_DRIVER UEFI_DRIVER DXE_RUNTIME_DRIVER UEFI_APPLICATION
+  CONSTRUCTOR                    = PlatformHookSerialPortInitialize
+
+[Sources]
+  Fdt16550SerialPortHookLib.c
+
+[LibraryClasses]
+  BaseLib
+  PcdLib
+  HobLib
+
+[Packages]
+  Platform/Loongson/LoongArchQemuPkg/Loongson.dec
+  EmbeddedPkg/EmbeddedPkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+
+[Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterBase
+
+[Guids]
+  gEarly16550UartBaseAddressGuid
diff --git a/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.c b/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.c
new file mode 100644
index 0000000000..c713c6e9d6
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.c
@@ -0,0 +1,900 @@
+/** @file
+  16550 UART Serial Port library functions
+
+  Copyright (c) 2022, Loongson Limited. All rights reserved.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Base.h>
+#include <Library/SerialPortLib.h>
+#include <Library/PcdLib.h>
+#include <Library/IoLib.h>
+#include <Library/PlatformHookLib.h>
+#include <Library/BaseLib.h>
+#include <Guid/FdtHob.h>
+#include <libfdt.h>
+
+//
+// PCI Defintions.
+//
+#define PCI_BRIDGE_32_BIT_IO_SPACE  0x01
+
+//
+// 16550 UART register offsets and bitfields
+//
+#define R_UART_RXBUF         0    // LCR_DLAB = 0
+#define R_UART_TXBUF         0    // LCR_DLAB = 0
+#define R_UART_BAUD_LOW      0    // LCR_DLAB = 1
+#define R_UART_BAUD_HIGH     1    // LCR_DLAB = 1
+#define R_UART_IER           1    // LCR_DLAB = 0
+#define R_UART_FCR           2
+#define B_UART_FCR_FIFOE     BIT0
+#define B_UART_FCR_FIFO64    BIT5
+#define R_UART_LCR           3
+#define B_UART_LCR_DLAB      BIT7
+#define R_UART_MCR           4
+#define B_UART_MCR_DTRC      BIT0
+#define B_UART_MCR_RTS       BIT1
+#define R_UART_LSR           5
+#define B_UART_LSR_RXRDY     BIT0
+#define B_UART_LSR_TXRDY     BIT5
+#define B_UART_LSR_TEMT      BIT6
+#define R_UART_MSR           6
+#define B_UART_MSR_CTS       BIT4
+#define B_UART_MSR_DSR       BIT5
+#define B_UART_MSR_RI        BIT6
+#define B_UART_MSR_DCD       BIT7
+
+/**
+  Read an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is read from
+  MMIO space.  If PcdSerialUseMmio is FALSE, then the value is read from I/O space.  The
+  parameter Offset is added to the base address of the 16550 registers that is specified
+  by PcdSerialRegisterBase. PcdSerialRegisterAccessWidth specifies the MMIO space access
+  width and defaults to 8 bit access, and supports 8 or 32 bit access.
+
+  @param  Base    The base address register of UART device.
+  @param  Offset  The offset of the 16550 register to read.
+
+  @return The value read from the 16550 register.
+**/
+UINT8
+SerialPortReadRegister (
+  UINTN  Base,
+  UINTN  Offset
+  )
+{
+  if (PcdGetBool (PcdSerialUseMmio)) {
+    if (PcdGet8 (PcdSerialRegisterAccessWidth) == 32) {
+      return (UINT8)MmioRead32 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
+    }
+
+    return MmioRead8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
+  } else {
+    return IoRead8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride));
+  }
+}
+
+/**
+  Write an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is written to
+  MMIO space.  If PcdSerialUseMmio is FALSE, then the value is written to I/O space.  The
+  parameter Offset is added to the base address of the 16550 registers that is specified
+  by PcdSerialRegisterBase. PcdSerialRegisterAccessWidth specifies the MMIO space access
+  width and defaults to 8 bit access, and supports 8 or 32 bit access.
+
+  @param  Base    The base address register of UART device.
+  @param  Offset  The offset of the 16550 register to write.
+  @param  Value   The value to write to the 16550 register specified by Offset.
+
+  @return The value written to the 16550 register.
+**/
+UINT8
+SerialPortWriteRegister (
+  UINTN  Base,
+  UINTN  Offset,
+  UINT8  Value
+  )
+{
+  if (PcdGetBool (PcdSerialUseMmio)) {
+    if (PcdGet8 (PcdSerialRegisterAccessWidth) == 32) {
+      return (UINT8)MmioWrite32 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), (UINT8)Value);
+    }
+
+    return MmioWrite8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), Value);
+  } else {
+    return IoWrite8 (Base + Offset * PcdGet32 (PcdSerialRegisterStride), Value);
+  }
+}
+
+/** Get the UART base address of the console serial-port from the DT.
+
+  This function fetches the node referenced in the "stdout-path"
+  property of the "chosen" node and returns the base address of
+  the console UART.
+
+  @param [in]   Fdt                   Pointer to a Flattened Device Tree (Fdt).
+  @param [out]  SerialConsoleAddress  If success, contains the base address
+                                      of the console serial-port.
+
+  @retval EFI_SUCCESS             The function completed successfully.
+  @retval EFI_NOT_FOUND           Console serial-port info not found in DT.
+  @retval EFI_INVALID_PARAMETER   Invalid parameter.
+**/
+STATIC
+EFI_STATUS
+EFIAPI
+GetSerialConsolePortAddress (
+  IN  CONST VOID    *Fdt,
+  OUT       UINT64  *SerialConsoleAddress
+  )
+{
+  CONST CHAR8   *Prop;
+  INT32         PropSize;
+  CONST CHAR8   *Path;
+  INT32         PathLen;
+  INT32         ChosenNode;
+  INT32         SerialConsoleNode;
+  INT32         Len;
+  CONST CHAR8   *NodeStatus;
+  CONST UINT64  *RegProperty;
+
+  if ((Fdt == NULL) || (fdt_check_header (Fdt) != 0)) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  // The "chosen" node resides at the root of the DT. Fetch it.
+  ChosenNode = fdt_path_offset (Fdt, "/chosen");
+  if (ChosenNode < 0) {
+    return EFI_NOT_FOUND;
+  }
+
+  Prop = fdt_getprop (Fdt, ChosenNode, "stdout-path", &PropSize);
+  if (PropSize < 0) {
+    return EFI_NOT_FOUND;
+  }
+
+  // Determine the actual path length, as a colon terminates the path.
+  Path = ScanMem8 (Prop, ':', PropSize);
+  if (Path == NULL) {
+    PathLen = AsciiStrLen (Prop);
+  } else {
+    PathLen = Path - Prop;
+  }
+
+  // Aliases cannot start with a '/', so it must be the actual path.
+  if (Prop[0] == '/') {
+    SerialConsoleNode = fdt_path_offset_namelen (Fdt, Prop, PathLen);
+  } else {
+    // Lookup the alias, as this contains the actual path.
+    Path = fdt_get_alias_namelen (Fdt, Prop, PathLen);
+    if (Path == NULL) {
+      return EFI_NOT_FOUND;
+    }
+
+    SerialConsoleNode = fdt_path_offset (Fdt, Path);
+  }
+
+  NodeStatus = fdt_getprop (Fdt, SerialConsoleNode, "status", &Len);
+  if ((NodeStatus != NULL) && (AsciiStrCmp (NodeStatus, "okay") != 0)) {
+    return EFI_NOT_FOUND;
+  }
+
+  RegProperty = fdt_getprop (Fdt, SerialConsoleNode, "reg", &Len);
+  if (Len != 16) {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  *SerialConsoleAddress = fdt64_to_cpu (ReadUnaligned64 (RegProperty));
+
+  return EFI_SUCCESS;
+}
+
+/**
+  Retrieve the I/O or MMIO base address register for the PCI UART device.
+
+  This function assumes Root Bus Numer is Zero, and enables I/O and MMIO in PCI UART
+  Device if they are not already enabled.
+
+  @return  The base address register of the UART device.
+**/
+UINTN
+GetSerialRegisterBase (
+  VOID
+  )
+{
+  VOID    *Base;
+  RETURN_STATUS  Status;
+  UINT64  SerialConsoleAddress;
+
+  Base = (VOID*)(UINTN)PcdGet64 (PcdDeviceTreeBase);
+  Status = GetSerialConsolePortAddress (Base, &SerialConsoleAddress);
+  if (RETURN_ERROR (Status)) {
+    return (UINTN)0;
+  }
+
+  return SerialConsoleAddress;
+}
+
+/**
+  Return whether the hardware flow control signal allows writing.
+
+  @param  SerialRegisterBase The base address register of UART device.
+
+  @retval TRUE  The serial port is writable.
+  @retval FALSE The serial port is not writable.
+**/
+BOOLEAN
+SerialPortWritable (
+  UINTN  SerialRegisterBase
+  )
+{
+  if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+    if (PcdGetBool (PcdSerialDetectCable)) {
+      //
+      // Wait for both DSR and CTS to be set
+      //   DSR is set if a cable is connected.
+      //   CTS is set if it is ok to transmit data
+      //
+      //   DSR  CTS  Description                               Action
+      //   ===  ===  ========================================  ========
+      //    0    0   No cable connected.                       Wait
+      //    0    1   No cable connected.                       Wait
+      //    1    0   Cable connected, but not clear to send.   Wait
+      //    1    1   Cable connected, and clear to send.       Transmit
+      //
+      return (BOOLEAN)((SerialPortReadRegister (SerialRegisterBase, R_UART_MSR) & (B_UART_MSR_DSR | B_UART_MSR_CTS)) == (B_UART_MSR_DSR | B_UART_MSR_CTS));
+    } else {
+      //
+      // Wait for both DSR and CTS to be set OR for DSR to be clear.
+      //   DSR is set if a cable is connected.
+      //   CTS is set if it is ok to transmit data
+      //
+      //   DSR  CTS  Description                               Action
+      //   ===  ===  ========================================  ========
+      //    0    0   No cable connected.                       Transmit
+      //    0    1   No cable connected.                       Transmit
+      //    1    0   Cable connected, but not clear to send.   Wait
+      //    1    1   Cable connected, and clar to send.        Transmit
+      //
+      return (BOOLEAN)((SerialPortReadRegister (SerialRegisterBase, R_UART_MSR) & (B_UART_MSR_DSR | B_UART_MSR_CTS)) != (B_UART_MSR_DSR));
+    }
+  }
+
+  return TRUE;
+}
+
+/**
+  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
+  )
+{
+  UINTN          SerialRegisterBase;
+  UINT32         Divisor;
+  UINT32         CurrentDivisor;
+  BOOLEAN        Initialized;
+
+  //
+  // Calculate divisor for baud generator
+  //    Ref_Clk_Rate / Baud_Rate / 16
+  //
+  Divisor = PcdGet32 (PcdSerialClockRate) / (PcdGet32 (PcdSerialBaudRate) * 16);
+  if ((PcdGet32 (PcdSerialClockRate) % (PcdGet32 (PcdSerialBaudRate) * 16)) >= PcdGet32 (PcdSerialBaudRate) * 8) {
+    Divisor++;
+  }
+
+  //
+  // Get the base address of the serial port in either I/O or MMIO space
+  //
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return RETURN_DEVICE_ERROR;
+  }
+
+  //
+  // See if the serial port is already initialized
+  //
+  Initialized = TRUE;
+  if ((SerialPortReadRegister (SerialRegisterBase, R_UART_LCR) & 0x3F) != (PcdGet8 (PcdSerialLineControl) & 0x3F)) {
+    Initialized = FALSE;
+  }
+
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, (UINT8)(SerialPortReadRegister (SerialRegisterBase, R_UART_LCR) | B_UART_LCR_DLAB));
+  CurrentDivisor  =  SerialPortReadRegister (SerialRegisterBase, R_UART_BAUD_HIGH) << 8;
+  CurrentDivisor |= (UINT32)SerialPortReadRegister (SerialRegisterBase, R_UART_BAUD_LOW);
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, (UINT8)(SerialPortReadRegister (SerialRegisterBase, R_UART_LCR) & ~B_UART_LCR_DLAB));
+  if (CurrentDivisor != Divisor) {
+    Initialized = FALSE;
+  }
+
+  if (Initialized) {
+    return RETURN_SUCCESS;
+  }
+
+  //
+  // Wait for the serial port to be ready.
+  // Verify that both the transmit FIFO and the shift register are empty.
+  //
+  while ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) != (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) {
+  }
+
+  //
+  // Configure baud rate
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, B_UART_LCR_DLAB);
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_BAUD_HIGH, (UINT8)(Divisor >> 8));
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_BAUD_LOW, (UINT8)(Divisor & 0xff));
+
+  //
+  // Clear DLAB and configure Data Bits, Parity, and Stop Bits.
+  // Strip reserved bits from PcdSerialLineControl
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, (UINT8)(PcdGet8 (PcdSerialLineControl) & 0x3F));
+
+  //
+  // Enable and reset FIFOs
+  // Strip reserved bits from PcdSerialFifoControl
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_FCR, 0x00);
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_FCR, (UINT8)(PcdGet8 (PcdSerialFifoControl) & (B_UART_FCR_FIFOE | B_UART_FCR_FIFO64)));
+
+  //
+  // Set FIFO Polled Mode by clearing IER after setting FCR
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_IER, 0x00);
+
+  //
+  // Put Modem Control Register(MCR) into its reset state of 0x00.
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, 0x00);
+
+  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           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
+EFIAPI
+SerialPortWrite (
+  IN UINT8  *Buffer,
+  IN UINTN  NumberOfBytes
+  )
+{
+  UINTN  SerialRegisterBase;
+  UINTN  Result;
+  UINTN  Index;
+  UINTN  FifoSize;
+
+  if (Buffer == NULL) {
+    return 0;
+  }
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return 0;
+  }
+
+  if (NumberOfBytes == 0) {
+    //
+    // Flush the hardware
+    //
+
+    //
+    // Wait for both the transmit FIFO and shift register empty.
+    //
+    while ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) != (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) {
+    }
+
+    //
+    // Wait for the hardware flow control signal
+    //
+    while (!SerialPortWritable (SerialRegisterBase)) {
+    }
+
+    return 0;
+  }
+
+  //
+  // Compute the maximum size of the Tx FIFO
+  //
+  FifoSize = 1;
+  if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFOE) != 0) {
+    if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFO64) == 0) {
+      FifoSize = 16;
+    } else {
+      FifoSize = PcdGet32 (PcdSerialExtendedTxFifoSize);
+    }
+  }
+
+  Result = NumberOfBytes;
+  while (NumberOfBytes != 0) {
+    //
+    // Wait for the serial port to be ready, to make sure both the transmit FIFO
+    // and shift register empty.
+    //
+    while ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) != (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) {
+    }
+
+    //
+    // Fill then entire Tx FIFO
+    //
+    for (Index = 0; Index < FifoSize && NumberOfBytes != 0; Index++, NumberOfBytes--, Buffer++) {
+      //
+      // Wait for the hardware flow control signal
+      //
+      while (!SerialPortWritable (SerialRegisterBase)) {
+      }
+
+      //
+      // Write byte to the transmit buffer.
+      //
+      SerialPortWriteRegister (SerialRegisterBase, R_UART_TXBUF, *Buffer);
+    }
+  }
+
+  return Result;
+}
+
+/**
+  Reads data from a serial device into a buffer.
+
+  @param  Buffer           Pointer to the data buffer to store the data read from the serial device.
+  @param  NumberOfBytes    Number of bytes to read from the serial device.
+
+  @retval 0                NumberOfBytes is 0.
+  @retval >0               The number of bytes read from the serial device.
+                           If this value is less than NumberOfBytes, then the read operation failed.
+**/
+UINTN
+EFIAPI
+SerialPortRead (
+  OUT UINT8  *Buffer,
+  IN  UINTN  NumberOfBytes
+  )
+{
+  UINTN  SerialRegisterBase;
+  UINTN  Result;
+  UINT8  Mcr;
+
+  if (NULL == Buffer) {
+    return 0;
+  }
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return 0;
+  }
+
+  Mcr = (UINT8)(SerialPortReadRegister (SerialRegisterBase, R_UART_MCR) & ~B_UART_MCR_RTS);
+
+  for (Result = 0; NumberOfBytes-- != 0; Result++, Buffer++) {
+    //
+    // Wait for the serial port to have some data.
+    //
+    while ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & B_UART_LSR_RXRDY) == 0) {
+      if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+        //
+        // Set RTS to let the peer send some data
+        //
+        SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, (UINT8)(Mcr | B_UART_MCR_RTS));
+      }
+    }
+
+    if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+      //
+      // Clear RTS to prevent peer from sending data
+      //
+      SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, Mcr);
+    }
+
+    //
+    // Read byte from the receive buffer.
+    //
+    *Buffer = SerialPortReadRegister (SerialRegisterBase, R_UART_RXBUF);
+  }
+
+  return Result;
+}
+
+/**
+  Polls a serial device to see if there is any data waiting to be read.
+
+  Polls aserial 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
+  )
+{
+  UINTN  SerialRegisterBase;
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return FALSE;
+  }
+
+  //
+  // Read the serial port status
+  //
+  if ((SerialPortReadRegister (SerialRegisterBase, R_UART_LSR) & B_UART_LSR_RXRDY) != 0) {
+    if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+      //
+      // Clear RTS to prevent peer from sending data
+      //
+      SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, (UINT8)(SerialPortReadRegister (SerialRegisterBase, R_UART_MCR) & ~B_UART_MCR_RTS));
+    }
+
+    return TRUE;
+  }
+
+  if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+    //
+    // Set RTS to let the peer send some data
+    //
+    SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, (UINT8)(SerialPortReadRegister (SerialRegisterBase, R_UART_MCR) | B_UART_MCR_RTS));
+  }
+
+  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
+  )
+{
+  UINTN  SerialRegisterBase;
+  UINT8  Mcr;
+
+  //
+  // First determine the parameter is invalid.
+  //
+  if ((Control & (~(EFI_SERIAL_REQUEST_TO_SEND | EFI_SERIAL_DATA_TERMINAL_READY |
+                    EFI_SERIAL_HARDWARE_FLOW_CONTROL_ENABLE))) != 0)
+  {
+    return RETURN_UNSUPPORTED;
+  }
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return RETURN_UNSUPPORTED;
+  }
+
+  //
+  // Read the Modem Control Register.
+  //
+  Mcr  = SerialPortReadRegister (SerialRegisterBase, R_UART_MCR);
+  Mcr &= (~(B_UART_MCR_DTRC | B_UART_MCR_RTS));
+
+  if ((Control & EFI_SERIAL_DATA_TERMINAL_READY) == EFI_SERIAL_DATA_TERMINAL_READY) {
+    Mcr |= B_UART_MCR_DTRC;
+  }
+
+  if ((Control & EFI_SERIAL_REQUEST_TO_SEND) == EFI_SERIAL_REQUEST_TO_SEND) {
+    Mcr |= B_UART_MCR_RTS;
+  }
+
+  //
+  // Write the Modem Control Register.
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_MCR, Mcr);
+
+  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
+  )
+{
+  UINTN  SerialRegisterBase;
+  UINT8  Msr;
+  UINT8  Mcr;
+  UINT8  Lsr;
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return RETURN_UNSUPPORTED;
+  }
+
+  *Control = 0;
+
+  //
+  // Read the Modem Status Register.
+  //
+  Msr = SerialPortReadRegister (SerialRegisterBase, R_UART_MSR);
+
+  if ((Msr & B_UART_MSR_CTS) == B_UART_MSR_CTS) {
+    *Control |= EFI_SERIAL_CLEAR_TO_SEND;
+  }
+
+  if ((Msr & B_UART_MSR_DSR) == B_UART_MSR_DSR) {
+    *Control |= EFI_SERIAL_DATA_SET_READY;
+  }
+
+  if ((Msr & B_UART_MSR_RI) == B_UART_MSR_RI) {
+    *Control |= EFI_SERIAL_RING_INDICATE;
+  }
+
+  if ((Msr & B_UART_MSR_DCD) == B_UART_MSR_DCD) {
+    *Control |= EFI_SERIAL_CARRIER_DETECT;
+  }
+
+  //
+  // Read the Modem Control Register.
+  //
+  Mcr = SerialPortReadRegister (SerialRegisterBase, R_UART_MCR);
+
+  if ((Mcr & B_UART_MCR_DTRC) == B_UART_MCR_DTRC) {
+    *Control |= EFI_SERIAL_DATA_TERMINAL_READY;
+  }
+
+  if ((Mcr & B_UART_MCR_RTS) == B_UART_MCR_RTS) {
+    *Control |= EFI_SERIAL_REQUEST_TO_SEND;
+  }
+
+  if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {
+    *Control |= EFI_SERIAL_HARDWARE_FLOW_CONTROL_ENABLE;
+  }
+
+  //
+  // Read the Line Status Register.
+  //
+  Lsr = SerialPortReadRegister (SerialRegisterBase, R_UART_LSR);
+
+  if ((Lsr & (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) == (B_UART_LSR_TEMT | B_UART_LSR_TXRDY)) {
+    *Control |= EFI_SERIAL_OUTPUT_BUFFER_EMPTY;
+  }
+
+  if ((Lsr & B_UART_LSR_RXRDY) == 0) {
+    *Control |= EFI_SERIAL_INPUT_BUFFER_EMPTY;
+  }
+
+  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
+  )
+{
+  UINTN   SerialRegisterBase;
+  UINT32  SerialBaudRate;
+  UINTN   Divisor;
+  UINT8   Lcr;
+  UINT8   LcrData;
+  UINT8   LcrParity;
+  UINT8   LcrStop;
+
+  SerialRegisterBase = GetSerialRegisterBase ();
+  if (SerialRegisterBase == 0) {
+    return RETURN_UNSUPPORTED;
+  }
+
+  //
+  // Check for default settings and fill in actual values.
+  //
+  if (*BaudRate == 0) {
+    *BaudRate = PcdGet32 (PcdSerialBaudRate);
+  }
+
+  SerialBaudRate = (UINT32)*BaudRate;
+
+  if (*DataBits == 0) {
+    LcrData   = (UINT8)(PcdGet8 (PcdSerialLineControl) & 0x3);
+    *DataBits = LcrData + 5;
+  } else {
+    if ((*DataBits < 5) || (*DataBits > 8)) {
+      return RETURN_INVALID_PARAMETER;
+    }
+
+    //
+    // Map 5..8 to 0..3
+    //
+    LcrData = (UINT8)(*DataBits - (UINT8)5);
+  }
+
+  if (*Parity == DefaultParity) {
+    LcrParity = (UINT8)((PcdGet8 (PcdSerialLineControl) >> 3) & 0x7);
+    switch (LcrParity) {
+      case 0:
+        *Parity = NoParity;
+        break;
+
+      case 3:
+        *Parity = EvenParity;
+        break;
+
+      case 1:
+        *Parity = OddParity;
+        break;
+
+      case 7:
+        *Parity = SpaceParity;
+        break;
+
+      case 5:
+        *Parity = MarkParity;
+        break;
+
+      default:
+        break;
+    }
+  } else {
+    switch (*Parity) {
+      case NoParity:
+        LcrParity = 0;
+        break;
+
+      case EvenParity:
+        LcrParity = 3;
+        break;
+
+      case OddParity:
+        LcrParity = 1;
+        break;
+
+      case SpaceParity:
+        LcrParity = 7;
+        break;
+
+      case MarkParity:
+        LcrParity = 5;
+        break;
+
+      default:
+        return RETURN_INVALID_PARAMETER;
+    }
+  }
+
+  if (*StopBits == DefaultStopBits) {
+    LcrStop = (UINT8)((PcdGet8 (PcdSerialLineControl) >> 2) & 0x1);
+    switch (LcrStop) {
+      case 0:
+        *StopBits = OneStopBit;
+        break;
+
+      case 1:
+        if (*DataBits == 5) {
+          *StopBits = OneFiveStopBits;
+        } else {
+          *StopBits = TwoStopBits;
+        }
+
+        break;
+
+      default:
+        break;
+    }
+  } else {
+    switch (*StopBits) {
+      case OneStopBit:
+        LcrStop = 0;
+        break;
+
+      case OneFiveStopBits:
+      case TwoStopBits:
+        LcrStop = 1;
+        break;
+
+      default:
+        return RETURN_INVALID_PARAMETER;
+    }
+  }
+
+  //
+  // Calculate divisor for baud generator
+  //    Ref_Clk_Rate / Baud_Rate / 16
+  //
+  Divisor = PcdGet32 (PcdSerialClockRate) / (SerialBaudRate * 16);
+  if ((PcdGet32 (PcdSerialClockRate) % (SerialBaudRate * 16)) >= SerialBaudRate * 8) {
+    Divisor++;
+  }
+
+  //
+  // Configure baud rate
+  //
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, B_UART_LCR_DLAB);
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_BAUD_HIGH, (UINT8)(Divisor >> 8));
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_BAUD_LOW, (UINT8)(Divisor & 0xff));
+
+  //
+  // Clear DLAB and configure Data Bits, Parity, and Stop Bits.
+  // Strip reserved bits from line control value
+  //
+  Lcr = (UINT8)((LcrParity << 3) | (LcrStop << 2) | LcrData);
+  SerialPortWriteRegister (SerialRegisterBase, R_UART_LCR, (UINT8)(Lcr & 0x3F));
+
+  return RETURN_SUCCESS;
+}
diff --git a/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.inf b/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.inf
new file mode 100644
index 0000000000..ee7b5fda18
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Library/SerialPortLib/EarlySerialPortLib16550.inf
@@ -0,0 +1,46 @@
+## @file
+#  SerialPortLib instance for 16550 UART.
+#
+#  Copyright (c) 2022, Loongson Limited. All rights reserved.
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = EarlySerialPortLib16550
+  FILE_GUID                      = f4fb883d-8138-4f29-bb0c-c574e9312c74
+  MODULE_TYPE                    = BASE
+  VERSION_STRING                 = 1.1
+  LIBRARY_CLASS                  = SerialPortLib
+
+[Packages]
+  EmbeddedPkg/EmbeddedPkg.dec
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  Platform/Loongson/LoongArchQemuPkg/Loongson.dec
+
+[LibraryClasses]
+  BaseLib
+  IoLib
+  PcdLib
+  FdtLib
+
+[Sources]
+  EarlySerialPortLib16550.c
+
+[Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterAccessWidth     ## SOMETIMES_CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio                 ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseHardwareFlowControl  ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialDetectCable             ## SOMETIMES_CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterBase            ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialBaudRate                ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialLineControl             ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialFifoControl             ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate               ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialPciDeviceInfo           ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialExtendedTxFifoSize      ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterStride          ## CONSUMES
+  gLoongArchQemuPkgTokenSpaceGuid.PcdDeviceTreeBase               ## CONSUMES
-- 
2.31.1



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