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 */
smh_putc(struct uart_port * port,int c)24 static void smh_putc(struct uart_port *port, int 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
smh_write(struct console * con,const char * s,unsigned n)39 static 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
45 static int
early_smh_setup(struct earlycon_device * device,const char * opt)46 __init early_smh_setup(struct earlycon_device *device, const char *opt)
47 {
48 device->con->write = smh_write;
49 return 0;
50 }
51 EARLYCON_DECLARE(smh, early_smh_setup);
52