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MIPS: Add 8250/16550 serial early printk driver

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Signed-off-by: Yoichi Yuasa <yuasa@linux-mips.org>
Cc: linux-mips <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/947/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Yoichi Yuasa 2010-02-08 20:59:39 +09:00 committed by Ralf Baechle
parent 31c4867d6c
commit 7cd93b8935
4 changed files with 83 additions and 0 deletions
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8
arch/mips/Kconfig.debug
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@ -20,6 +20,14 @@ config EARLY_PRINTK
doesn't cooperate with an X server. You should normally say N here,
unless you want to debug such a crash.
config EARLY_PRINTK_8250
bool "8250/16550 and compatible serial early printk driver"
depends on EARLY_PRINTK
default n
help
If you say Y here, it will be possible to use a 8250/16550 serial
port as the boot console.
config CMDLINE_BOOL
bool "Built-in kernel command line"
default n

8
arch/mips/include/asm/setup.h
View File

@ -5,6 +5,14 @@
extern void setup_early_printk(void);
#ifdef CONFIG_EARLY_PRINTK_8250
extern void setup_8250_early_printk_port(unsigned long base,
unsigned int reg_shift, unsigned int timeout);
#else
static inline void setup_8250_early_printk_port(unsigned long base,
unsigned int reg_shift, unsigned int timeout) {}
#endif
extern void set_handler(unsigned long offset, void *addr, unsigned long len);
extern void set_uncached_handler(unsigned long offset, void *addr, unsigned long len);

1
arch/mips/kernel/Makefile
View File

@ -84,6 +84,7 @@ obj-$(CONFIG_GPIO_TXX9) += gpio_txx9.o
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_EARLY_PRINTK_8250) += early_printk_8250.o
obj-$(CONFIG_SPINLOCK_TEST) += spinlock_test.o
obj-$(CONFIG_MIPS_MACHINE) += mips_machine.o

66
arch/mips/kernel/early_printk_8250.c Normal file
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@ -0,0 +1,66 @@
/*
* 8250/16550-type serial ports prom_putchar()
*
* Copyright (C) 2010 Yoichi Yuasa <yuasa@linux-mips.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/io.h>
#include <linux/serial_core.h>
#include <linux/serial_reg.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);
}