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commit 0a76092a63809a0e72e3e9552acadf42869c0293
Author: Yoichi Yuasa <yuasa@linux-mips.org>
Date: Mon Feb 8 20:59:39 2010 +0900
MIPS: Add 8250/16550 serial early printk driver
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>
--- 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
--- 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);
--- 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
--- /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);
+}
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