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

   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, 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
  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);
  52