[mirror_edk2.git] / MdeModulePkg / Library / BaseSerialPortLib16550 / BaseSerialPortLib16550.c

/** @file\r
  16550 UART Serial Port library functions\r
\r
  Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>\r
  This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
#include <Base.h>\r
#include <Library/SerialPortLib.h>\r
#include <Library/PcdLib.h>\r
#include <Library/IoLib.h>\r
#include <Library/PlatformHookLib.h>\r
\r
//\r
// 16550 UART register offsets and bitfields\r
//\r
#define R_UART_RXBUF          0\r
#define R_UART_TXBUF          0\r
#define R_UART_BAUD_LOW       0\r
#define R_UART_BAUD_HIGH      1\r
#define R_UART_FCR            2\r
#define   B_UART_FCR_FIFOE    BIT0\r
#define   B_UART_FCR_FIFO64   BIT5\r
#define R_UART_LCR            3\r
#define   B_UART_LCR_DLAB     BIT7\r
#define R_UART_MCR            4\r
#define   B_UART_MCR_RTS      BIT1\r
#define R_UART_LSR            5\r
#define   B_UART_LSR_RXRDY    BIT0\r
#define   B_UART_LSR_TXRDY    BIT5\r
#define   B_UART_LSR_TEMT     BIT6\r
#define R_UART_MSR            6\r
#define   B_UART_MSR_CTS      BIT4\r
#define   B_UART_MSR_DCD      BIT7\r
\r
/**\r
  Read an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is read from \r
  MMIO space.  If PcdSerialUseMmio is FALSE, then the value is read from I/O space.  The\r
  parameter Offset is added to the base address of the 16550 registers that is specified \r
  by PcdSerialRegisterBase. \r
  \r
  @param  Offset  The offset of the 16550 register to read.\r
\r
  @return The value read from the 16550 register.\r
\r
**/\r
UINT8\r
SerialPortReadRegister (\r
  UINTN  Offset\r
  )\r
{\r
  if (PcdGetBool (PcdSerialUseMmio)) {\r
    return MmioRead8 ((UINTN)PcdGet64 (PcdSerialRegisterBase) + Offset);\r
  } else {\r
    return IoRead8 ((UINT16)PcdGet64 (PcdSerialRegisterBase) + Offset);\r
  }\r
}\r
\r
/**\r
  Write an 8-bit 16550 register.  If PcdSerialUseMmio is TRUE, then the value is written to\r
  MMIO space.  If PcdSerialUseMmio is FALSE, then the value is written to I/O space.  The\r
  parameter Offset is added to the base address of the 16550 registers that is specified \r
  by PcdSerialRegisterBase. \r
  \r
  @param  Offset  The offset of the 16550 register to read.\r
\r
  @return The value written to the 16550 register.\r
\r
**/\r
UINT8\r
SerialPortWriteRegister (\r
  UINTN  Offset,\r
  UINT8  Value\r
  )\r
{\r
  if (PcdGetBool (PcdSerialUseMmio)) {\r
    return MmioWrite8 ((UINTN)PcdGet64 (PcdSerialRegisterBase) + Offset, Value);\r
  } else {\r
    return IoWrite8 ((UINT16)PcdGet64 (PcdSerialRegisterBase) + Offset, Value);\r
  }\r
}\r
\r
/**\r
  Initialize the serial device hardware.\r
  \r
  If no initialization is required, then return RETURN_SUCCESS.\r
  If the serial device was successfuly initialized, then return RETURN_SUCCESS.\r
  If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.\r
  \r
  @retval RETURN_SUCCESS        The serial device was initialized.\r
  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.\r
\r
**/\r
RETURN_STATUS\r
EFIAPI\r
SerialPortInitialize (\r
  VOID\r
  )\r
{\r
  RETURN_STATUS  Status;\r
  UINTN          Divisor;\r
  BOOLEAN        Initialized;\r
\r
  //\r
  // Perform platform specific initialization required to enable use of the 16550 device\r
  // at the location specified by PcdSerialUseMmio and PcdSerialRegisterBase.\r
  //\r
  Status = PlatformHookSerialPortInitialize ();\r
  if (RETURN_ERROR (Status)) {\r
    return Status;\r
  }\r
\r
  //\r
  // See if the serial port is already initialized\r
  //\r
  Initialized = TRUE;\r
  if ((SerialPortReadRegister (R_UART_FCR) & (B_UART_FCR_FIFOE | B_UART_FCR_FIFO64)) !=\r
      (PcdGet8 (PcdSerialFifoControl)      & (B_UART_FCR_FIFOE | B_UART_FCR_FIFO64))     ) {\r
    Initialized = FALSE;\r
  }\r
  if ((SerialPortReadRegister (R_UART_LCR) & 0x3F) != (PcdGet8 (PcdSerialLineControl) & 0x3F)) {\r
    Initialized = FALSE;\r
  }\r
  SerialPortWriteRegister (R_UART_LCR, (UINT8)(SerialPortReadRegister (R_UART_LCR) | B_UART_LCR_DLAB));\r
  Divisor =  SerialPortReadRegister (R_UART_BAUD_HIGH) << 8;\r
  Divisor |= SerialPortReadRegister (R_UART_BAUD_LOW);\r
  SerialPortWriteRegister (R_UART_LCR, (UINT8)(SerialPortReadRegister (R_UART_LCR) & ~B_UART_LCR_DLAB));\r
  if (Divisor != 115200 / PcdGet32 (PcdSerialBaudRate)) {\r
    Initialized = FALSE;\r
  }\r
  if (Initialized) {\r
    return RETURN_SUCCESS;\r
  }\r
  \r
  //\r
  // Configure baud rate\r
  //\r
  Divisor = 115200 / PcdGet32 (PcdSerialBaudRate);\r
  SerialPortWriteRegister (R_UART_LCR, B_UART_LCR_DLAB);\r
  SerialPortWriteRegister (R_UART_BAUD_HIGH, (UINT8) (Divisor >> 8));\r
  SerialPortWriteRegister (R_UART_BAUD_LOW, (UINT8) (Divisor & 0xff));\r
\r
  //\r
  // Clear DLAB and configure Data Bits, Parity, and Stop Bits.\r
  // Strip reserved bits from PcdSerialLineControl\r
  //\r
  SerialPortWriteRegister (R_UART_LCR, (UINT8)(PcdGet8 (PcdSerialLineControl) & 0x3F));\r
\r
  //\r
  // Enable and reset FIFOs\r
  // Strip reserved bits from PcdSerialFifoControl\r
  //\r
  SerialPortWriteRegister (R_UART_FCR, (UINT8)(PcdGet8 (PcdSerialFifoControl) & 0x17));\r
\r
  //\r
  // Put Modem Control Register(MCR) into its reset state of 0x00.\r
  //  \r
  SerialPortWriteRegister (R_UART_MCR, 0x00);\r
  \r
  return RETURN_SUCCESS;\r
}\r
\r
/**\r
  Write data from buffer to serial device. \r
 \r
  Writes NumberOfBytes data bytes from Buffer to the serial device.  \r
  The number of bytes actually written to the serial device is returned.\r
  If the return value is less than NumberOfBytes, then the write operation failed.\r
\r
  If Buffer is NULL, then ASSERT(). \r
\r
  If NumberOfBytes is zero, then return 0.\r
\r
  @param  Buffer           Pointer to the data buffer to be written.\r
  @param  NumberOfBytes    Number of bytes to written to the serial device.\r
\r
  @retval 0                NumberOfBytes is 0.\r
  @retval >0               The number of bytes written to the serial device.  \r
                           If this value is less than NumberOfBytes, then the read operation failed.\r
\r
**/\r
UINTN\r
EFIAPI\r
SerialPortWrite (\r
  IN UINT8     *Buffer,\r
  IN UINTN     NumberOfBytes\r
)\r
{\r
  UINTN  Result;\r
  UINTN  Index;\r
  UINTN  FifoSize;\r
\r
  if (Buffer == NULL) {\r
    return 0;\r
  }\r
\r
  //\r
  // Compute the maximum size of the Tx FIFO\r
  //\r
  FifoSize = 1;\r
  if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFOE) != 0) {\r
    if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFO64) == 0) {\r
      FifoSize = 16;\r
    } else {\r
      FifoSize = 64;\r
    }\r
  }\r
  \r
  Result = NumberOfBytes;\r
  while (NumberOfBytes != 0) {\r
    //\r
    // Wait for the serial port to be ready, to make sure both the transmit FIFO\r
    // and shift register empty.\r
    //\r
    while ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_TEMT) == 0);\r
\r
    //\r
    // Fill then entire Tx FIFO\r
    //\r
    for (Index = 0; Index < FifoSize && NumberOfBytes != 0; Index++, NumberOfBytes--, Buffer++) {\r
      if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
        //\r
        // Wait for notification from peer to send data\r
        //\r
        while ((SerialPortReadRegister (R_UART_MSR) & (B_UART_MSR_CTS | B_UART_MSR_DCD)) == B_UART_MSR_DCD);\r
      }\r
      \r
      //\r
      // Write byte to the transmit buffer.\r
      //\r
      SerialPortWriteRegister (R_UART_TXBUF, *Buffer);\r
    }\r
  }\r
  return Result;\r
}\r
\r
/**\r
  Reads data from a serial device into a buffer.\r
\r
  @param  Buffer           Pointer to the data buffer to store the data read from the serial device.\r
  @param  NumberOfBytes    Number of bytes to read from the serial device.\r
\r
  @retval 0                NumberOfBytes is 0.\r
  @retval >0               The number of bytes read from the serial device.  \r
                           If this value is less than NumberOfBytes, then the read operation failed.\r
\r
**/\r
UINTN\r
EFIAPI\r
SerialPortRead (\r
  OUT UINT8     *Buffer,\r
  IN  UINTN     NumberOfBytes\r
)\r
{\r
  UINTN  Result;\r
  UINT8  Mcr;\r
\r
  if (NULL == Buffer) {\r
    return 0;\r
  }\r
\r
  Mcr = (UINT8)(SerialPortReadRegister (R_UART_MCR) & ~B_UART_MCR_RTS);\r
  \r
  for (Result = 0; NumberOfBytes-- != 0; Result++, Buffer++) {\r
    //\r
    // Wait for the serial port to have some data.\r
    //\r
    while ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_RXRDY) == 0) {\r
      if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
        //\r
        // Set RTS to let the peer send some data\r
        //\r
        SerialPortWriteRegister (R_UART_MCR, (UINT8)(Mcr | B_UART_MCR_RTS));\r
      }\r
    }\r
    if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
      //\r
      // Clear RTS to prevent peer from sending data\r
      //\r
      SerialPortWriteRegister (R_UART_MCR, Mcr);\r
    }\r
    \r
    //\r
    // Read byte from the receive buffer.\r
    //\r
    *Buffer = SerialPortReadRegister (R_UART_RXBUF);\r
  }\r
  \r
  return Result;\r
}\r
\r
/**\r
  Polls a serial device to see if there is any data waiting to be read.\r
\r
  Polls aserial device to see if there is any data waiting to be read.\r
  If there is data waiting to be read from the serial device, then TRUE is returned.\r
  If there is no data waiting to be read from the serial device, then FALSE is returned.\r
\r
  @retval TRUE             Data is waiting to be read from the serial device.\r
  @retval FALSE            There is no data waiting to be read from the serial device.\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
SerialPortPoll (\r
  VOID\r
  )\r
{\r
  //\r
  // Read the serial port status\r
  //\r
  if ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_RXRDY) != 0) {\r
    if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
      //\r
      // Clear RTS to prevent peer from sending data\r
      //\r
      SerialPortWriteRegister (R_UART_MCR, (UINT8)(SerialPortReadRegister (R_UART_MCR) & ~B_UART_MCR_RTS));\r
    }\r
    return TRUE;\r
  }    \r
  \r
  if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
    //\r
    // Set RTS to let the peer send some data\r
    //\r
    SerialPortWriteRegister (R_UART_MCR, (UINT8)(SerialPortReadRegister (R_UART_MCR) | B_UART_MCR_RTS));\r
  }\r
  \r
  return FALSE;\r
}\r
Commit	Line	Data
467d15ae	1	/** @file\r
	2	16550 UART Serial Port library functions\r
	3	\r
	4	Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>\r
	5	This program and the accompanying materials\r
	6	are licensed and made available under the terms and conditions of the BSD License\r
	7	which accompanies this distribution. The full text of the license may be found at\r
	8	http://opensource.org/licenses/bsd-license.php\r
	9	\r
	10	THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
	11	WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
	12	\r
	13	**/\r
	14	\r
	15	#include <Base.h>\r
	16	#include <Library/SerialPortLib.h>\r
	17	#include <Library/PcdLib.h>\r
	18	#include <Library/IoLib.h>\r
	19	#include <Library/PlatformHookLib.h>\r
	20	\r
	21	//\r
	22	// 16550 UART register offsets and bitfields\r
	23	//\r
	24	#define R_UART_RXBUF 0\r
	25	#define R_UART_TXBUF 0\r
	26	#define R_UART_BAUD_LOW 0\r
	27	#define R_UART_BAUD_HIGH 1\r
	28	#define R_UART_FCR 2\r
	29	#define B_UART_FCR_FIFOE BIT0\r
	30	#define B_UART_FCR_FIFO64 BIT5\r
	31	#define R_UART_LCR 3\r
	32	#define B_UART_LCR_DLAB BIT7\r
	33	#define R_UART_MCR 4\r
	34	#define B_UART_MCR_RTS BIT1\r
	35	#define R_UART_LSR 5\r
	36	#define B_UART_LSR_RXRDY BIT0\r
	37	#define B_UART_LSR_TXRDY BIT5\r
	38	#define B_UART_LSR_TEMT BIT6\r
	39	#define R_UART_MSR 6\r
	40	#define B_UART_MSR_CTS BIT4\r
	41	#define B_UART_MSR_DCD BIT7\r
	42	\r
	43	/**\r
	44	Read an 8-bit 16550 register. If PcdSerialUseMmio is TRUE, then the value is read from \r
	45	MMIO space. If PcdSerialUseMmio is FALSE, then the value is read from I/O space. The\r
	46	parameter Offset is added to the base address of the 16550 registers that is specified \r
	47	by PcdSerialRegisterBase. \r
	48	\r
	49	@param Offset The offset of the 16550 register to read.\r
	50	\r
	51	@return The value read from the 16550 register.\r
	52	\r
	53	**/\r
	54	UINT8\r
	55	SerialPortReadRegister (\r
	56	UINTN Offset\r
	57	)\r
	58	{\r
	59	if (PcdGetBool (PcdSerialUseMmio)) {\r
	60	return MmioRead8 ((UINTN)PcdGet64 (PcdSerialRegisterBase) + Offset);\r
	61	} else {\r
	62	return IoRead8 ((UINT16)PcdGet64 (PcdSerialRegisterBase) + Offset);\r
	63	}\r
	64	}\r
65	\r
66	/**\r
67	Write an 8-bit 16550 register. If PcdSerialUseMmio is TRUE, then the value is written to\r
68	MMIO space. If PcdSerialUseMmio is FALSE, then the value is written to I/O space. The\r
69	parameter Offset is added to the base address of the 16550 registers that is specified \r
70	by PcdSerialRegisterBase. \r
71	\r
72	@param Offset The offset of the 16550 register to read.\r
73	\r
74	@return The value written to the 16550 register.\r
75	\r
76	**/\r
77	UINT8\r
78	SerialPortWriteRegister (\r
79	UINTN Offset,\r
80	UINT8 Value\r
81	)\r
82	{\r
83	if (PcdGetBool (PcdSerialUseMmio)) {\r
84	return MmioWrite8 ((UINTN)PcdGet64 (PcdSerialRegisterBase) + Offset, Value);\r
85	} else {\r
86	return IoWrite8 ((UINT16)PcdGet64 (PcdSerialRegisterBase) + Offset, Value);\r
87	}\r
88	}\r
89	\r
90	/**\r
91	Initialize the serial device hardware.\r
92	\r
93	If no initialization is required, then return RETURN_SUCCESS.\r
94	If the serial device was successfuly initialized, then return RETURN_SUCCESS.\r
95	If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.\r
96	\r
97	@retval RETURN_SUCCESS The serial device was initialized.\r
98	@retval RETURN_DEVICE_ERROR The serial device could not be initialized.\r
99	\r
100	**/\r
101	RETURN_STATUS\r
102	EFIAPI\r
103	SerialPortInitialize (\r
104	VOID\r
105	)\r
106	{\r
107	RETURN_STATUS Status;\r
108	UINTN Divisor;\r
109	BOOLEAN Initialized;\r
110	\r
111	//\r
112	// Perform platform specific initialization required to enable use of the 16550 device\r
113	// at the location specified by PcdSerialUseMmio and PcdSerialRegisterBase.\r
114	//\r
115	Status = PlatformHookSerialPortInitialize ();\r
116	if (RETURN_ERROR (Status)) {\r
117	return Status;\r
118	}\r
119	\r
120	//\r
121	// See if the serial port is already initialized\r
122	//\r
123	Initialized = TRUE;\r
124	if ((SerialPortReadRegister (R_UART_FCR) & (B_UART_FCR_FIFOE \| B_UART_FCR_FIFO64)) !=\r
125	(PcdGet8 (PcdSerialFifoControl) & (B_UART_FCR_FIFOE \| B_UART_FCR_FIFO64)) ) {\r
126	Initialized = FALSE;\r
127	}\r
128	if ((SerialPortReadRegister (R_UART_LCR) & 0x3F) != (PcdGet8 (PcdSerialLineControl) & 0x3F)) {\r
129	Initialized = FALSE;\r
130	}\r
f2ad9497	131	SerialPortWriteRegister (R_UART_LCR, (UINT8)(SerialPortReadRegister (R_UART_LCR) \| B_UART_LCR_DLAB));\r
	132	Divisor = SerialPortReadRegister (R_UART_BAUD_HIGH) << 8;\r
	133	Divisor \|= SerialPortReadRegister (R_UART_BAUD_LOW);\r
	134	SerialPortWriteRegister (R_UART_LCR, (UINT8)(SerialPortReadRegister (R_UART_LCR) & ~B_UART_LCR_DLAB));\r
467d15ae	135	if (Divisor != 115200 / PcdGet32 (PcdSerialBaudRate)) {\r
	136	Initialized = FALSE;\r
	137	}\r
	138	if (Initialized) {\r
	139	return RETURN_SUCCESS;\r
	140	}\r
	141	\r
	142	//\r
	143	// Configure baud rate\r
	144	//\r
	145	Divisor = 115200 / PcdGet32 (PcdSerialBaudRate);\r
	146	SerialPortWriteRegister (R_UART_LCR, B_UART_LCR_DLAB);\r
	147	SerialPortWriteRegister (R_UART_BAUD_HIGH, (UINT8) (Divisor >> 8));\r
	148	SerialPortWriteRegister (R_UART_BAUD_LOW, (UINT8) (Divisor & 0xff));\r
	149	\r
	150	//\r
	151	// Clear DLAB and configure Data Bits, Parity, and Stop Bits.\r
	152	// Strip reserved bits from PcdSerialLineControl\r
	153	//\r
f2ad9497	154	SerialPortWriteRegister (R_UART_LCR, (UINT8)(PcdGet8 (PcdSerialLineControl) & 0x3F));\r
467d15ae	155	\r
	156	//\r
	157	// Enable and reset FIFOs\r
	158	// Strip reserved bits from PcdSerialFifoControl\r
	159	//\r
f2ad9497	160	SerialPortWriteRegister (R_UART_FCR, (UINT8)(PcdGet8 (PcdSerialFifoControl) & 0x17));\r
467d15ae	161	\r
	162	//\r
	163	// Put Modem Control Register(MCR) into its reset state of 0x00.\r
	164	// \r
	165	SerialPortWriteRegister (R_UART_MCR, 0x00);\r
	166	\r
	167	return RETURN_SUCCESS;\r
	168	}\r
	169	\r
	170	/**\r
	171	Write data from buffer to serial device. \r
	172	\r
	173	Writes NumberOfBytes data bytes from Buffer to the serial device. \r
	174	The number of bytes actually written to the serial device is returned.\r
	175	If the return value is less than NumberOfBytes, then the write operation failed.\r
	176	\r
	177	If Buffer is NULL, then ASSERT(). \r
	178	\r
	179	If NumberOfBytes is zero, then return 0.\r
	180	\r
	181	@param Buffer Pointer to the data buffer to be written.\r
	182	@param NumberOfBytes Number of bytes to written to the serial device.\r
	183	\r
	184	@retval 0 NumberOfBytes is 0.\r
	185	@retval >0 The number of bytes written to the serial device. \r
	186	If this value is less than NumberOfBytes, then the read operation failed.\r
	187	\r
	188	**/\r
	189	UINTN\r
	190	EFIAPI\r
	191	SerialPortWrite (\r
	192	IN UINT8 *Buffer,\r
	193	IN UINTN NumberOfBytes\r
	194	)\r
	195	{\r
	196	UINTN Result;\r
	197	UINTN Index;\r
	198	UINTN FifoSize;\r
	199	\r
	200	if (Buffer == NULL) {\r
	201	return 0;\r
	202	}\r
	203	\r
	204	//\r
	205	// Compute the maximum size of the Tx FIFO\r
	206	//\r
	207	FifoSize = 1;\r
	208	if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFOE) != 0) {\r
	209	if ((PcdGet8 (PcdSerialFifoControl) & B_UART_FCR_FIFO64) == 0) {\r
	210	FifoSize = 16;\r
	211	} else {\r
	212	FifoSize = 64;\r
	213	}\r
	214	}\r
	215	\r
	216	Result = NumberOfBytes;\r
	217	while (NumberOfBytes != 0) {\r
	218	//\r
	219	// Wait for the serial port to be ready, to make sure both the transmit FIFO\r
	220	// and shift register empty.\r
	221	//\r
	222	while ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_TEMT) == 0);\r
	223	\r
	224	//\r
225	// Fill then entire Tx FIFO\r
226	//\r
227	for (Index = 0; Index < FifoSize && NumberOfBytes != 0; Index++, NumberOfBytes--, Buffer++) {\r
228	if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
229	//\r
230	// Wait for notification from peer to send data\r
231	//\r
232	while ((SerialPortReadRegister (R_UART_MSR) & (B_UART_MSR_CTS \| B_UART_MSR_DCD)) == B_UART_MSR_DCD);\r
233	}\r
234	\r
235	//\r
236	// Write byte to the transmit buffer.\r
237	//\r
238	SerialPortWriteRegister (R_UART_TXBUF, *Buffer);\r
239	}\r
240	}\r
241	return Result;\r
242	}\r
243	\r
244	/**\r
245	Reads data from a serial device into a buffer.\r
246	\r
247	@param Buffer Pointer to the data buffer to store the data read from the serial device.\r
248	@param NumberOfBytes Number of bytes to read from the serial device.\r
249	\r
250	@retval 0 NumberOfBytes is 0.\r
251	@retval >0 The number of bytes read from the serial device. \r
252	If this value is less than NumberOfBytes, then the read operation failed.\r
253	\r
254	**/\r
255	UINTN\r
256	EFIAPI\r
257	SerialPortRead (\r
258	OUT UINT8 *Buffer,\r
259	IN UINTN NumberOfBytes\r
260	)\r
261	{\r
262	UINTN Result;\r
263	UINT8 Mcr;\r
264	\r
265	if (NULL == Buffer) {\r
266	return 0;\r
267	}\r
268	\r
f2ad9497	269	Mcr = (UINT8)(SerialPortReadRegister (R_UART_MCR) & ~B_UART_MCR_RTS);\r
467d15ae	270	\r
	271	for (Result = 0; NumberOfBytes-- != 0; Result++, Buffer++) {\r
	272	//\r
	273	// Wait for the serial port to have some data.\r
	274	//\r
	275	while ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_RXRDY) == 0) {\r
	276	if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
	277	//\r
	278	// Set RTS to let the peer send some data\r
	279	//\r
f2ad9497	280	SerialPortWriteRegister (R_UART_MCR, (UINT8)(Mcr \| B_UART_MCR_RTS));\r
467d15ae	281	}\r
	282	}\r
	283	if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
	284	//\r
	285	// Clear RTS to prevent peer from sending data\r
	286	//\r
	287	SerialPortWriteRegister (R_UART_MCR, Mcr);\r
	288	}\r
	289	\r
	290	//\r
	291	// Read byte from the receive buffer.\r
	292	//\r
	293	*Buffer = SerialPortReadRegister (R_UART_RXBUF);\r
	294	}\r
	295	\r
	296	return Result;\r
	297	}\r
	298	\r
	299	/**\r
	300	Polls a serial device to see if there is any data waiting to be read.\r
	301	\r
	302	Polls aserial device to see if there is any data waiting to be read.\r
	303	If there is data waiting to be read from the serial device, then TRUE is returned.\r
	304	If there is no data waiting to be read from the serial device, then FALSE is returned.\r
	305	\r
	306	@retval TRUE Data is waiting to be read from the serial device.\r
	307	@retval FALSE There is no data waiting to be read from the serial device.\r
	308	\r
	309	**/\r
	310	BOOLEAN\r
	311	EFIAPI\r
	312	SerialPortPoll (\r
	313	VOID\r
	314	)\r
	315	{\r
	316	//\r
	317	// Read the serial port status\r
	318	//\r
	319	if ((SerialPortReadRegister (R_UART_LSR) & B_UART_LSR_RXRDY) != 0) {\r
	320	if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
	321	//\r
	322	// Clear RTS to prevent peer from sending data\r
	323	//\r
f2ad9497	324	SerialPortWriteRegister (R_UART_MCR, (UINT8)(SerialPortReadRegister (R_UART_MCR) & ~B_UART_MCR_RTS));\r
467d15ae	325	}\r
	326	return TRUE;\r
	327	} \r
	328	\r
	329	if (PcdGetBool (PcdSerialUseHardwareFlowControl)) {\r
	330	//\r
	331	// Set RTS to let the peer send some data\r
	332	//\r
f2ad9497	333	SerialPortWriteRegister (R_UART_MCR, (UINT8)(SerialPortReadRegister (R_UART_MCR) \| B_UART_MCR_RTS));\r
467d15ae	334	}\r
	335	\r
	336	return FALSE;\r
	337	}\r