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Commit 7cd93b89 authored by Yoichi Yuasa's avatar Yoichi Yuasa Committed by Ralf Baechle
Browse files

MIPS: Add 8250/16550 serial early printk driver 



Signed-off-by: default avatarYoichi Yuasa <yuasa@linux-mips.org>
Cc: linux-mips <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/947/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 31c4867d

arch/mips/Kconfig.debug

+8 −0
Original line number Diff line number Diff line
@@ -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

arch/mips/include/asm/setup.h

+8 −0
Original line number Diff line number Diff line
@@ -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);

arch/mips/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/mips/kernel/early_printk_8250.c

0 → 100644
+66 −0
Original line number Diff line number Diff line 
/*

 *  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);

}