drivers/console/console.S

/*
 * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of ARM nor the names of its contributors may be used
 * to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
#include <asm_macros.S>

	.globl	console_init
	.globl	console_uninit
	.globl	console_putc
	.globl	console_getc

	/*
	 *  The console base is in the data section and not in .bss
	 *  even though it is zero-init. In particular, this allows
	 *  the console functions to start using this variable before
	 *  the runtime memory is initialized for images which do not
	 *  need to copy the .data section from ROM to RAM.
	 */
.section .data.console_base ; .align 3
	console_base: .quad 0x0

	/* -----------------------------------------------
	 * int console_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. It saves
	 * the console base to the data section.
	 * In: x0 - console base address
	 *     w1 - Uart clock in Hz
	 *     w2 - Baud rate
	 * out: return 1 on success else 0 on error
	 * Clobber list : x1 - x3
	 * -----------------------------------------------
	 */
func console_init
	/* Check the input base address */
	cbz	x0, init_fail
	adrp	x3, console_base
	str	x0, [x3, :lo12:console_base]
	b	console_core_init
init_fail:
	ret
endfunc console_init

	/* -----------------------------------------------
	 * void console_uninit(void)
	 * Function to finish the use of console driver.
	 * It sets the console_base as NULL so that any
	 * further invocation of `console_putc` or
	 * `console_getc` APIs would return error.
	 * -----------------------------------------------
	 */
func console_uninit
	mov	x0, #0
	adrp	x3, console_base
	str	x0, [x3, :lo12:console_base]
endfunc console_uninit

	/* ---------------------------------------------
	 * int console_putc(int c)
	 * Function to output a character over the
	 * console. It returns the character printed on
	 * success or -1 on error.
	 * In : x0 - character to be printed
	 * Out : return -1 on error else return character.
	 * Clobber list : x1, x2
	 * ---------------------------------------------
	 */
func console_putc
	adrp	x2, console_base
	ldr	x1, [x2, :lo12:console_base]
	b	console_core_putc
endfunc console_putc

	/* ---------------------------------------------
	 * int console_getc(void)
	 * Function to get a character from the console.
	 * It returns the character grabbed on success
	 * or -1 on error.
	 * Clobber list : x0, x1
	 * ---------------------------------------------
	 */
func console_getc
	adrp	x1, console_base
	ldr	x0, [x1, :lo12:console_base]
	b	console_core_getc
endfunc console_getc