diff options
-rw-r--r-- | arch/mips/Kconfig.debug | 8 | ||||
-rw-r--r-- | arch/mips/include/asm/setup.h | 8 | ||||
-rw-r--r-- | arch/mips/kernel/Makefile | 1 | ||||
-rw-r--r-- | arch/mips/kernel/early_printk_8250.c | 66 |
4 files changed, 83 insertions, 0 deletions
diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug index 37871f0..b147e70 100644 --- a/arch/mips/Kconfig.debug +++ b/arch/mips/Kconfig.debug @@ -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 diff --git a/arch/mips/include/asm/setup.h b/arch/mips/include/asm/setup.h index e26589e..d7bfdeb 100644 --- a/arch/mips/include/asm/setup.h +++ b/arch/mips/include/asm/setup.h @@ -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); diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile index 423d871..4bbece9 100644 --- a/arch/mips/kernel/Makefile +++ b/arch/mips/kernel/Makefile @@ -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 diff --git a/arch/mips/kernel/early_printk_8250.c b/arch/mips/kernel/early_printk_8250.c new file mode 100644 index 0000000..83cea37 --- /dev/null +++ b/arch/mips/kernel/early_printk_8250.c @@ -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); +} |