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