drivers/console/aarch32/skeleton_console.S

/*
 * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
#include <asm_macros.S>

	/*
	 * This file contains a skeleton console implementation that can
	 * be used as basis for a real console implementation by platforms
	 * that do not contain PL011 hardware.
	 */

	.globl	console_core_init
	.globl	console_core_putc
	.globl	console_core_getc
	.globl	console_core_flush

	/* -----------------------------------------------
	 * int console_core_init(uintptr_t base_addr,
	 * unsigned int uart_clk, unsigned int baud_rate)
	 * Function to initialize the console without a
	 * C Runtime to print debug information. This
	 * function will be accessed by console_init and
	 * crash reporting.
	 * In: r0 - console base address
	 *     r1 - Uart clock in Hz
	 *     r2 - Baud rate
	 * Out: return 1 on success else 0 on error
	 * Clobber list : r1, r2
	 * -----------------------------------------------
	 */
func console_core_init
	/* Check the input base address */
	cmp	r0, #0
	beq	core_init_fail
	/* Check baud rate and uart clock for sanity */
	cmp	r1, #0
	beq	core_init_fail
	cmp	r2, #0
	beq	core_init_fail
	/* Insert implementation here */
	mov	r0, #1
	bx	lr
core_init_fail:
	mov	r0, #0
	bx	lr
endfunc console_core_init

	/* --------------------------------------------------------
	 * int console_core_putc(int c, uintptr_t base_addr)
	 * Function to output a character over the console. It
	 * returns the character printed on success or -1 on error.
	 * In : r0 - character to be printed
	 *      r1 - console base address
	 * Out : return -1 on error else return character.
	 * Clobber list : r2
	 * --------------------------------------------------------
	 */
func console_core_putc
	/* Check the input parameter */
	cmp	r1, #0
	beq	putc_error
	/* Insert implementation here */
	bx	lr
putc_error:
	mov	r0, #-1
	bx	lr
endfunc console_core_putc

	/* ---------------------------------------------
	 * int console_core_getc(uintptr_t base_addr)
	 * Function to get a character from the console.
	 * It returns the character grabbed on success
	 * or -1 on error.
	 * In : r0 - console base address
	 * Clobber list : r0, r1
	 * ---------------------------------------------
	 */
func console_core_getc
	cmp	r0, #0
	beq	getc_error
	/* Insert implementation here */
	bx	lr
getc_error:
	mov	r0, #-1
	bx	lr
endfunc console_core_getc

	/* ---------------------------------------------
	 * int console_core_flush(uintptr_t base_addr)
	 * Function to force a write of all buffered
	 * data that hasn't been output.
	 * In : r0 - console base address
	 * Out : return -1 on error else return 0.
	 * Clobber list : r0, r1
	 * ---------------------------------------------
	 */
func console_core_flush
	cmp	r0, #0
	beq	flush_error
	/* Insert implementation here */
	mov	r0, #0
	bx	lr
flush_error:
	mov	r0, #-1
	bx	lr
endfunc console_core_flush