drivers/tty/serial/earlycon-riscv-sbi.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RISC-V SBI based earlycon
   4  *
   5  * Copyright (C) 2018 Anup Patel <anup@brainfault.org>
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/console.h>
   9 #include <linux/init.h>
  10 #include <linux/serial_core.h>
  11 #include <asm/sbi.h>
  12
  13 static void sbi_putc(struct uart_port *port, unsigned char c)
  14 {
  15         sbi_console_putchar(c);
  16 }
  17
  18 static void sbi_0_1_console_write(struct console *con,
  19                                   const char *s, unsigned int n)
  20 {
  21         struct earlycon_device *dev = con->data;
  22         uart_console_write(&dev->port, s, n, sbi_putc);
  23 }
  24
  25 static void sbi_dbcn_console_write(struct console *con,
  26                                    const char *s, unsigned int n)
  27 {
  28         int ret;
  29
  30         while (n) {
  31                 ret = sbi_debug_console_write(s, n);
  32                 if (ret < 0)
  33                         break;
  34
  35                 s += ret;
  36                 n -= ret;
  37         }
  38 }
  39
  40 static int __init early_sbi_setup(struct earlycon_device *device,
  41                                   const char *opt)
  42 {
  43         if (sbi_debug_console_available)
  44                 device->con->write = sbi_dbcn_console_write;
  45         else if (IS_ENABLED(CONFIG_RISCV_SBI_V01))
  46                 device->con->write = sbi_0_1_console_write;
  47         else
  48                 return -ENODEV;
  49
  50         return 0;
  51 }
  52 EARLYCON_DECLARE(sbi, early_sbi_setup);