| 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 | |
| 12 | static void __iomem *serial8250_base; |
| 13 | static unsigned int serial8250_reg_shift; |
| 14 | static unsigned int serial8250_tx_timeout; |
| 15 | |
| 16 | void 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 | |
| 24 | static inline u8 serial_in(int offset) |
| 25 | { |
| 26 | return readb(addr: serial8250_base + (offset << serial8250_reg_shift)); |
| 27 | } |
| 28 | |
| 29 | static inline void serial_out(int offset, char value) |
| 30 | { |
| 31 | writeb(val: value, addr: serial8250_base + (offset << serial8250_reg_shift)); |
| 32 | } |
| 33 | |
| 34 | void 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, value: c); |
| 54 | } |
| 55 |