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>

1 files changed, 107 insertions, 0 deletions

diff --git a/arch/microblaze/kernel/early_printk.c b/arch/microblaze/kernel/early_printk.c
new file mode 100644
index 000000000000..62cc78993f44
--- /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;
+}