1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 *  8250/16550-type serial ports prom_putchar()
 4 *
 5 *  Copyright (C) 2010  Yoichi Yuasa <yuasa@linux-mips.org>
 6 */
 7#include <linux/io.h>
 8#include <linux/serial_core.h>
 9#include <linux/serial_reg.h>
10#include <asm/setup.h>
11
12static void __iomem *serial8250_base;
13static unsigned int serial8250_reg_shift;
14static unsigned int serial8250_tx_timeout;
15
16void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift,
17				  unsigned int timeout)
18{
19	serial8250_base = (void __iomem *)base;
20	serial8250_reg_shift = reg_shift;
21	serial8250_tx_timeout = timeout;
22}
23
24static inline u8 serial_in(int offset)
25{
26	return readb(serial8250_base + (offset << serial8250_reg_shift));
27}
28
29static inline void serial_out(int offset, char value)
30{
31	writeb(value, serial8250_base + (offset << serial8250_reg_shift));
32}
33
34void prom_putchar(char c)
35{
36	unsigned int timeout;
37	int status, bits;
38
39	if (!serial8250_base)
40		return;
41
42	timeout = serial8250_tx_timeout;
43	bits = UART_LSR_TEMT | UART_LSR_THRE;
44
45	do {
46		status = serial_in(UART_LSR);
47
48		if (--timeout == 0)
49			break;
50	} while ((status & bits) != bits);
51
52	if (timeout)
53		serial_out(UART_TX, c);
54}

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 *  8250/16550-type serial ports prom_putchar()
 4 *
 5 *  Copyright (C) 2010  Yoichi Yuasa <yuasa@linux-mips.org>
 6 */
 7#include <linux/io.h>
 8#include <linux/serial_core.h>
 9#include <linux/serial_reg.h>
10#include <asm/setup.h>
11
12static void __iomem *serial8250_base;
13static unsigned int serial8250_reg_shift;
14static unsigned int serial8250_tx_timeout;
15
16void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift,
17				  unsigned int timeout)
18{
19	serial8250_base = (void __iomem *)base;
20	serial8250_reg_shift = reg_shift;
21	serial8250_tx_timeout = timeout;
22}
23
24static inline u8 serial_in(int offset)
25{
26	return readb(serial8250_base + (offset << serial8250_reg_shift));
27}
28
29static inline void serial_out(int offset, char value)
30{
31	writeb(value, serial8250_base + (offset << serial8250_reg_shift));
32}
33
34void prom_putchar(char c)
35{
36	unsigned int timeout;
37	int status, bits;
38
39	if (!serial8250_base)
40		return;
41
42	timeout = serial8250_tx_timeout;
43	bits = UART_LSR_TEMT | UART_LSR_THRE;
44
45	do {
46		status = serial_in(UART_LSR);
47
48		if (--timeout == 0)
49			break;
50	} while ((status & bits) != bits);
51
52	if (timeout)
53		serial_out(UART_TX, c);
54}