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authorYoichi Yuasa <yuasa@linux-mips.org>2010-02-08 12:59:39 +0100
committerRalf Baechle <ralf@linux-mips.org>2013-10-29 21:24:36 +0100
commit7cd93b893567906d9c9e9e1121667600b4cebbaf (patch)
tree2bbce647eb6d83d95be4d067d50093a9156b3f0e /arch/mips/kernel/early_printk_8250.c
parentMIPS: ZBOOT: Support LZ4 compression scheme (diff)
downloadlinux-7cd93b893567906d9c9e9e1121667600b4cebbaf.tar.xz
linux-7cd93b893567906d9c9e9e1121667600b4cebbaf.zip
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>
Diffstat (limited to 'arch/mips/kernel/early_printk_8250.c')
-rw-r--r--arch/mips/kernel/early_printk_8250.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/arch/mips/kernel/early_printk_8250.c b/arch/mips/kernel/early_printk_8250.c
new file mode 100644
index 000000000000..83cea3767556
--- /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);
+}