Signed-off-by: Yoichi Yuasa <yuasa@xxxxxxxxxxxxxx>
---
arch/mips/Kconfig.debug | 8 ++++
arch/mips/include/asm/setup.h | 9 ++++
arch/mips/kernel/Makefile | 1 +
arch/mips/kernel/early_printk_8250.c | 68 ++++++++++++++++++++++++++++++++++
4 files changed, 86 insertions(+), 0 deletions(-)
create mode 100644 arch/mips/kernel/early_printk_8250.c
diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index 32a010d..f5d739c 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 50511aa..7395b7f 100644
--- a/arch/mips/include/asm/setup.h
+++ b/arch/mips/include/asm/setup.h
@@ -5,6 +5,15 @@
#ifdef __KERNEL__
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
+
#endif /* __KERNEL__ */
#endif /* __SETUP_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 9326af5..03fc037 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_GPIO_TXX9) += gpio_txx9.o
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
+obj-$(CONFIG_EARLY_PRINTK_8250) += early_printk_8250.o
CFLAGS_cpu-bugs64.o = $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
diff --git a/arch/mips/kernel/early_printk_8250.c b/arch/mips/kernel/early_printk_8250.c
new file mode 100644
index 0000000..6faf8fd
--- /dev/null
+++ b/arch/mips/kernel/early_printk_8250.c
@@ -0,0 +1,68 @@
+/*
+ * 8250/16550-type serial ports prom_putchar()
+ *
+ * Copyright (C) 2010 Yoichi Yuasa <yuasa@xxxxxxxxxxxxxx>
+ *
+ * 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 unsigned long 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 = base;
+ serial8250_reg_shift = reg_shift;
+ serial8250_tx_timeout = timeout;
+}
+
+static inline u8 serial_in(int offset)
+{
+ return readb((void __iomem *)serial8250_base +
+ (offset << serial8250_reg_shift));
+}
+
+static inline void serial_out(int offset, char value)
+{
+ writeb(value, (void __iomem *)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);
+}
--
1.6.6.1
