arch/mips/loongson64/common/early_printk.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  early printk support
   3  *
   4  *  Copyright (c) 2009 Philippe Vachon <philippe@cowpig.ca>
   5  *  Copyright (c) 2009 Lemote Inc.
   6  *  Author: Wu Zhangjin, wuzhangjin@gmail.com
   7  */
   8 #include <linux/serial_reg.h>
   9 #include <asm/setup.h>
  10
  11 #include <loongson.h>
  12
  13 #define PORT(base, offset) (u8 *)(base + offset)
  14
  15 static inline unsigned int serial_in(unsigned char *base, int offset)
  16 {
  17         return readb(PORT(base, offset));
  18 }
  19
  20 static inline void serial_out(unsigned char *base, int offset, int value)
  21 {
  22         writeb(value, PORT(base, offset));
  23 }
  24
  25 void prom_putchar(char c)
  26 {
  27         int timeout;
  28         unsigned char *uart_base;
  29
  30         uart_base = (unsigned char *)_loongson_uart_base[0];
  31         timeout = 1024;
  32
  33         while (((serial_in(uart_base, UART_LSR) & UART_LSR_THRE) == 0) &&
  34                         (timeout-- > 0))
  35                 ;
  36
  37         serial_out(uart_base, UART_TX, c);
  38 }