microblaze_v8: early_printk support

Reviewed-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NStephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: NJohn Linn <john.linn@xilinx.com>
Acked-by: NJohn Williams <john.williams@petalogix.com>
Signed-off-by: NMichal Simek <monstr@monstr.eu>

arch/microblaze/kernel/early_printk.c

+/*
+ * Early printk support for Microblaze.
+ *
+ * Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>
+ * Copyright (C) 2007-2009 PetaLogix
+ * Copyright (C) 2003-2006 Yasushi SHOJI <yashi@atmark-techno.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/kernel.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/tty.h>
+#include <linux/io.h>
+#include <asm/processor.h>
+#include <linux/fcntl.h>
+#include <asm/setup.h>
+#include <asm/prom.h>
+
+static u32 early_console_initialized;
+static u32 base_addr;
+
+static void early_printk_putc(char c)
+{
+	/*
+	 * Limit how many times we'll spin waiting for TX FIFO status.
+	 * This will prevent lockups if the base address is incorrectly
+	 * set, or any other issue on the UARTLITE.
+	 * This limit is pretty arbitrary, unless we are at about 10 baud
+	 * we'll never timeout on a working UART.
+	 */
+
+	unsigned retries = 10000;
+	/* read status bit - 0x8 offset */
+	while (retries-- && (in_be32(base_addr + 8) & (1 << 3)))
+		;
+
+	/* Only attempt the iowrite if we didn't timeout */
+	/* write to TX_FIFO - 0x4 offset */
+	if (retries)
+		out_be32(base_addr + 4, c & 0xff);
+}
+
+static void early_printk_write(struct console *unused,
+					const char *s, unsigned n)
+{
+	while (*s && n-- > 0) {
+		early_printk_putc(*s);
+		if (*s == '\n')
+			early_printk_putc('\r');
+		s++;
+	}
+}
+
+static struct console early_serial_console = {
+	.name = "earlyser",
+	.write = early_printk_write,
+	.flags = CON_PRINTBUFFER,
+	.index = -1,
+};
+
+static struct console *early_console = &early_serial_console;
+
+void early_printk(const char *fmt, ...)
+{
+	char buf[512];
+	int n;
+	va_list ap;
+
+	if (early_console_initialized) {
+		va_start(ap, fmt);
+		n = vscnprintf(buf, 512, fmt, ap);
+		early_console->write(early_console, buf, n);
+		va_end(ap);
+	}
+}
+
+int __init setup_early_printk(char *opt)
+{
+	if (early_console_initialized)
+		return 1;
+
+	base_addr = early_uartlite_console();
+	if (base_addr) {
+		early_console_initialized = 1;
+		early_printk("early_printk_console is enabled at 0x%08x\n",
+							base_addr);
+
+		/* register_console(early_console); */
+
+		return 0;
+	} else
+		return 1;
+}
+
+void __init disable_early_printk(void)
+{
+	if (!early_console_initialized || !early_console)
+		return;
+	printk(KERN_WARNING "disabling early console\n");
+	unregister_console(early_console);
+	early_console_initialized = 0;
+}