mirror of https://gitee.com/openkylin/linux.git
67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
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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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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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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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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