1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Copyright (C) 2012 ARM Ltd.
 4 * Author: Marc Zyngier <marc.zyngier@arm.com>
 5 *
 6 * Adapted for ARM and earlycon:
 7 * Copyright (C) 2014 Linaro Ltd.
 8 * Author: Rob Herring <robh@kernel.org>
 9 */
10#include <linux/kernel.h>
11#include <linux/console.h>
12#include <linux/init.h>
13#include <linux/serial_core.h>
14
15#ifdef CONFIG_THUMB2_KERNEL
16#define SEMIHOST_SWI	"0xab"
17#else
18#define SEMIHOST_SWI	"0x123456"
19#endif
20
21/*
22 * Semihosting-based debug console
23 */
24static void smh_putc(struct uart_port *port, unsigned char c)
25{
26#ifdef CONFIG_ARM64
27	asm volatile("mov  x1, %0\n"
28		     "mov  x0, #3\n"
29		     "hlt  0xf000\n"
30		     : : "r" (&c) : "x0", "x1", "memory");
31#else
32	asm volatile("mov  r1, %0\n"
33		     "mov  r0, #3\n"
34		     "svc  " SEMIHOST_SWI "\n"
35		     : : "r" (&c) : "r0", "r1", "memory");
36#endif
37}
38
39static void smh_write(struct console *con, const char *s, unsigned n)
40{
41	struct earlycon_device *dev = con->data;
42	uart_console_write(&dev->port, s, n, smh_putc);
43}
44
45static int
46__init early_smh_setup(struct earlycon_device *device, const char *opt)
47{
48	device->con->write = smh_write;
49	return 0;
50}
51EARLYCON_DECLARE(smh, early_smh_setup);