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MdeModulePkg/Library/BaseSerialPortLib16550: Ensure FIFO Polled Mode 

Put the UART in FIFO Polled Mode by clearing IER after setting FCR.
Also, add comments to show DLAB state for registers 0 and 1.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Leo Duran <leo.duran@amd.com>
Cc: Star Zeng <star.zeng@intel.com>
CC: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
This commit is contained in:
Leo Duran 2018-05-25 03:07:30 +08:00 committed by Star Zeng
parent eb59431346
commit a05a8a5aa1
1 changed files with 12 additions and 4 deletions
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16
MdeModulePkg/Library/BaseSerialPortLib16550/BaseSerialPortLib16550.c
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@ -3,6 +3,8 @@
(C) Copyright 2014 Hewlett-Packard Development Company, L.P.<BR>
Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2018, AMD Incorporated. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
@ -30,10 +32,11 @@
//
// 16550 UART register offsets and bitfields
//
#define R_UART_RXBUF 0
#define R_UART_TXBUF 0
#define R_UART_BAUD_LOW 0
#define R_UART_BAUD_HIGH 1
#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
@ -553,6 +556,11 @@ SerialPortInitialize (
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.
//