microblaze_v8: early_printk support

Reviewed-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: John Linn <john.linn@xilinx.com>
Acked-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

diff --git a/arch/microblaze/kernel/early_printk.c b/arch/microblaze/kernel/early_printk.c
new file mode 100644 (file)
index 0000000..62cc789
--- /dev/null
+++ b/arch/microblaze/kernel/early_printk.c
@@ -0,0 +1,107 @@
+/*
+ * 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;
+}