LXR linux/drivers/tty/serial/earlycon-arm-semihost.c

   1/*
   2 * Copyright (C) 2012 ARM Ltd.
   3 * Author: Marc Zyngier <marc.zyngier@arm.com>
   4 *
   5 * Adapted for ARM and earlycon:
   6 * Copyright (C) 2014 Linaro Ltd.
   7 * Author: Rob Herring <robh@kernel.org>
   8 *
   9 * This program is free software: you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License version 2 as
  11 * published by the Free Software Foundation.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21#include <linux/kernel.h>
  22#include <linux/console.h>
  23#include <linux/init.h>
  24#include <linux/serial_core.h>
  25
  26#ifdef CONFIG_THUMB2_KERNEL
  27#define SEMIHOST_SWI    "0xab"
  28#else
  29#define SEMIHOST_SWI    "0x123456"
  30#endif
  31
  32/*
  33 * Semihosting-based debug console
  34 */
  35static void smh_putc(struct uart_port *port, int c)
  36{
  37#ifdef CONFIG_ARM64
  38        asm volatile("mov  x1, %0\n"
  39                     "mov  x0, #3\n"
  40                     "hlt  0xf000\n"
  41                     : : "r" (&c) : "x0", "x1", "memory");
  42#else
  43        asm volatile("mov  r1, %0\n"
  44                     "mov  r0, #3\n"
  45                     "svc  " SEMIHOST_SWI "\n"
  46                     : : "r" (&c) : "r0", "r1", "memory");
  47#endif
  48}
  49
  50static void smh_write(struct console *con, const char *s, unsigned n)
  51{
  52        struct earlycon_device *dev = con->data;
  53        uart_console_write(&dev->port, s, n, smh_putc);
  54}
  55
  56static int
  57__init early_smh_setup(struct earlycon_device *device, const char *opt)
  58{
  59        device->con->write = smh_write;
  60        return 0;
  61}
  62EARLYCON_DECLARE(smh, early_smh_setup);
  63