nios2: add early printk support

Signed-off-by: Ley Foon Tan <lftan@altera.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/arch/nios2/kernel/early_printk.c b/arch/nios2/kernel/early_printk.c
new file mode 100644
index 000000000000..c08e4c1486fc
--- /dev/null
+++ b/arch/nios2/kernel/early_printk.c
@@ -0,0 +1,118 @@
+/*
+ * Early printk for Nios2.
+ *
+ * Copyright (C) 2015, Altera Corporation
+ * Copyright (C) 2010, Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009, Wind River Systems Inc
+ *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+
+#include <asm/prom.h>
+
+static unsigned long base_addr;
+
+#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE)
+
+#define ALTERA_JTAGUART_DATA_REG		0
+#define ALTERA_JTAGUART_CONTROL_REG		4
+#define ALTERA_JTAGUART_CONTROL_WSPACE_MSK	0xFFFF0000
+#define ALTERA_JTAGUART_CONTROL_AC_MSK		0x00000400
+
+#define JUART_GET_CR() \
+	__builtin_ldwio((void *)(base_addr + ALTERA_JTAGUART_CONTROL_REG))
+#define JUART_SET_CR(v) \
+	__builtin_stwio((void *)(base_addr + ALTERA_JTAGUART_CONTROL_REG), v)
+#define JUART_SET_TX(v) \
+	__builtin_stwio((void *)(base_addr + ALTERA_JTAGUART_DATA_REG), v)
+
+static void early_console_write(struct console *con, const char *s, unsigned n)
+{
+	unsigned long status;
+
+	while (n-- && *s) {
+		while (((status = JUART_GET_CR())
+				& ALTERA_JTAGUART_CONTROL_WSPACE_MSK) == 0) {
+#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
+			if ((status & ALTERA_JTAGUART_CONTROL_AC_MSK) == 0)
+				return;	/* no connection activity */
+#endif
+		}
+		JUART_SET_TX(*s);
+		s++;
+	}
+}
+
+#elif defined(CONFIG_SERIAL_ALTERA_UART_CONSOLE)
+
+#define ALTERA_UART_TXDATA_REG		4
+#define ALTERA_UART_STATUS_REG		8
+#define ALTERA_UART_STATUS_TRDY		0x0040
+
+#define UART_GET_SR() \
+	__builtin_ldwio((void *)(base_addr + ALTERA_UART_STATUS_REG))
+#define UART_SET_TX(v) \
+	__builtin_stwio((void *)(base_addr + ALTERA_UART_TXDATA_REG), v)
+
+static void early_console_putc(char c)
+{
+	while (!(UART_GET_SR() & ALTERA_UART_STATUS_TRDY))
+		;
+
+	UART_SET_TX(c);
+}
+
+static void early_console_write(struct console *con, const char *s, unsigned n)
+{
+	while (n-- && *s) {
+		early_console_putc(*s);
+		if (*s == '\n')
+			early_console_putc('\r');
+		s++;
+	}
+}
+
+#else
+# error Neither SERIAL_ALTERA_JTAGUART_CONSOLE nor SERIAL_ALTERA_UART_CONSOLE \
+selected
+#endif
+
+static struct console early_console_prom = {
+	.name	= "early",
+	.write	= early_console_write,
+	.flags	= CON_PRINTBUFFER | CON_BOOT,
+	.index	= -1
+};
+
+void __init setup_early_printk(void)
+{
+#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE) ||	\
+	defined(CONFIG_SERIAL_ALTERA_UART_CONSOLE)
+	base_addr = of_early_console();
+#else
+	base_addr = 0;
+#endif
+
+	if (!base_addr)
+		return;
+
+#if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
+	/* Clear activity bit so BYPASS doesn't stall if we've used JTAG for
+	 * downloading the kernel. This might cause early data to be lost even
+	 * if the JTAG terminal is running.
+	 */
+	JUART_SET_CR(JUART_GET_CR() | ALTERA_JTAGUART_CONTROL_AC_MSK);
+#endif
+
+	early_console = &early_console_prom;
+	register_console(early_console);
+	pr_info("early_console initialized at 0x%08lx\n", base_addr);
+}