128 lines
4.5 KiB
ArmAsm
128 lines
4.5 KiB
ArmAsm
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/**************************************************************************
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* dm320/dm320_lowputc.S
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*
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* Copyright (C) 2007 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name Gregory Nutt nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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**************************************************************************/
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/**************************************************************************
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* Included Files
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**************************************************************************/
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#include <nuttx/config.h>
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#include "up_internal.h"
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#include "up_arch.h"
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/**************************************************************************
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* Private Definitions
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**************************************************************************/
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/**************************************************************************
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* Private Types
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**************************************************************************/
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/**************************************************************************
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* Private Function Prototypes
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**************************************************************************/
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/**************************************************************************
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* Global Variables
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**************************************************************************/
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/**************************************************************************
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* Private Variables
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**************************************************************************/
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/**************************************************************************
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* Private Functions
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**************************************************************************/
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/**************************************************************************
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* Public Functions
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**************************************************************************/
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/**************************************************************************
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* Name: up_lowputc
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**************************************************************************/
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/* This assembly language version has the advantage that it can does not
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* require a C stack and uses only r0-r1. Hence it can be used during
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* early boot phases.
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*/
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.text
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.global up_lowputc
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.type up_lowputc, function
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up_lowputc:
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/* On entry, r0 holds the character to be printed */
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#ifdef CONFIG_UART0_SERIAL_CONSOLE
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ldr r2, =DM320_UART0_REGISTER_BASE /* r2=UART0 base */
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#else
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ldr r2, =DM320_UART1_REGISTER_BASE /* r2=UART1 base */
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#endif
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/* Poll the TX fifo trigger level bit of the UART_SSR
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* register. When the bit is non-zero, the TX FIFO is no
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* longer full
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*/
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1: ldrh r1, [r2, #UART_SR]
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tst r1, #UART_SR_TFTI
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beq 1b
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/* Send the character by writing it into the UART_DTRR
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* register.
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*/
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strh r0, [r2, #UART_DTRR]
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/* Wait for the tranmsit regiser to be emptied. This is
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* detemined when TX register empty bit of the SR is zero.
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*/
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2: ldrh r1, [r2, #UART_SR]
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tst r1, #UART_SR_TREF
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bne 2b
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/* If the character that we just sent was a linefeed,
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* then send a carriage return as well.
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*/
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teq r0, #'\n'
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moveq r0, #'\r'
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beq 1b
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/* And return */
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mov pc, lr
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