125 lines
3.8 KiB
Diff
125 lines
3.8 KiB
Diff
commit 0a76092a63809a0e72e3e9552acadf42869c0293
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Author: Yoichi Yuasa <yuasa@linux-mips.org>
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Date: Mon Feb 8 20:59:39 2010 +0900
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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>
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Cc: linux-mips <linux-mips@linux-mips.org>
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Patchwork: https://patchwork.linux-mips.org/patch/947/
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Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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--- a/arch/mips/Kconfig.debug
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+++ b/arch/mips/Kconfig.debug
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@@ -20,6 +20,14 @@ config EARLY_PRINTK
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doesn't cooperate with an X server. You should normally say N here,
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unless you want to debug such a crash.
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+config EARLY_PRINTK_8250
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+ bool "8250/16550 and compatible serial early printk driver"
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+ depends on EARLY_PRINTK
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+ default n
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+ help
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+ If you say Y here, it will be possible to use a 8250/16550 serial
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+ port as the boot console.
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+
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config CMDLINE_BOOL
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bool "Built-in kernel command line"
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default n
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--- a/arch/mips/include/asm/setup.h
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+++ b/arch/mips/include/asm/setup.h
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@@ -5,6 +5,14 @@
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extern void setup_early_printk(void);
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+#ifdef CONFIG_EARLY_PRINTK_8250
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+extern void setup_8250_early_printk_port(unsigned long base,
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+ unsigned int reg_shift, unsigned int timeout);
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+#else
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+static inline void setup_8250_early_printk_port(unsigned long base,
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+ unsigned int reg_shift, unsigned int timeout) {}
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+#endif
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+
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extern void set_handler(unsigned long offset, void *addr, unsigned long len);
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extern void set_uncached_handler(unsigned long offset, void *addr, unsigned long len);
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--- a/arch/mips/kernel/Makefile
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+++ b/arch/mips/kernel/Makefile
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@@ -84,6 +84,7 @@ obj-$(CONFIG_GPIO_TXX9) += gpio_txx9.o
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obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
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obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
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obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
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+obj-$(CONFIG_EARLY_PRINTK_8250) += early_printk_8250.o
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obj-$(CONFIG_SPINLOCK_TEST) += spinlock_test.o
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obj-$(CONFIG_MIPS_MACHINE) += mips_machine.o
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--- /dev/null
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+++ b/arch/mips/kernel/early_printk_8250.c
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@@ -0,0 +1,66 @@
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+/*
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+ * 8250/16550-type serial ports prom_putchar()
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+ *
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+ * Copyright (C) 2010 Yoichi Yuasa <yuasa@linux-mips.org>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation; either version 2 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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+ */
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+#include <linux/io.h>
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+#include <linux/serial_core.h>
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+#include <linux/serial_reg.h>
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+
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+static void __iomem *serial8250_base;
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+static unsigned int serial8250_reg_shift;
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+static unsigned int serial8250_tx_timeout;
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+
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+void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift,
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+ unsigned int timeout)
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+{
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+ serial8250_base = (void __iomem *)base;
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+ serial8250_reg_shift = reg_shift;
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+ serial8250_tx_timeout = timeout;
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+}
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+
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+static inline u8 serial_in(int offset)
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+{
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+ return readb(serial8250_base + (offset << serial8250_reg_shift));
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+}
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+
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+static inline void serial_out(int offset, char value)
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+{
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+ writeb(value, serial8250_base + (offset << serial8250_reg_shift));
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+}
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+
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+void prom_putchar(char c)
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+{
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+ unsigned int timeout;
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+ int status, bits;
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+
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+ if (!serial8250_base)
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+ return;
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+
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+ timeout = serial8250_tx_timeout;
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+ bits = UART_LSR_TEMT | UART_LSR_THRE;
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+
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+ do {
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+ status = serial_in(UART_LSR);
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+
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+ if (--timeout == 0)
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+ break;
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+ } while ((status & bits) != bits);
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+
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+ if (timeout)
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+ serial_out(UART_TX, c);
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+}
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