// SPDX-License-Identifier: GPL-2.0-or-later /* * 8250/16550-type serial ports prom_putchar() * * Copyright (C) 2010 Yoichi Yuasa <yuasa@linux-mips.org> */ #include <linux/io.h> #include <linux/serial_core.h> #include <linux/serial_reg.h> #include <asm/setup.h> static void __iomem *serial8250_base; static unsigned int serial8250_reg_shift; static unsigned int serial8250_tx_timeout; void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift, unsigned int timeout) { serial8250_base = (void __iomem *)base; serial8250_reg_shift = reg_shift; serial8250_tx_timeout = timeout; } static inline u8 serial_in(int offset) { return readb(serial8250_base + (offset << serial8250_reg_shift)); } static inline void serial_out(int offset, char value) { writeb(value, serial8250_base + (offset << serial8250_reg_shift)); } void prom_putchar(char c) { unsigned int timeout; int status, bits; if (!serial8250_base) return; timeout = serial8250_tx_timeout; bits = UART_LSR_TEMT | UART_LSR_THRE; do { status = serial_in(UART_LSR); if (--timeout == 0) break; } while ((status & bits) != bits); if (timeout) serial_out(UART_TX, c); }