arch/microblaze/kernel/early_printk.c

   1 /*
   2  * Early printk support for Microblaze.
   3  *
   4  * Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>
   5  * Copyright (C) 2007-2009 PetaLogix
   6  * Copyright (C) 2003-2006 Yasushi SHOJI <yashi@atmark-techno.com>
   7  *
   8  * This file is subject to the terms and conditions of the GNU General Public
   9  * License. See the file "COPYING" in the main directory of this archive
  10  * for more details.
  11  */
  12
  13 #include <linux/console.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/string.h>
  17 #include <linux/tty.h>
  18 #include <linux/io.h>
  19 #include <asm/processor.h>
  20 #include <linux/fcntl.h>
  21 #include <asm/setup.h>
  22 #include <asm/prom.h>
  23
  24 static u32 early_console_initialized;
  25 static u32 base_addr;
  26
  27 static void early_printk_putc(char c)
  28 {
  29         /*
  30          * Limit how many times we'll spin waiting for TX FIFO status.
  31          * This will prevent lockups if the base address is incorrectly
  32          * set, or any other issue on the UARTLITE.
  33          * This limit is pretty arbitrary, unless we are at about 10 baud
  34          * we'll never timeout on a working UART.
  35          */
  36
  37         unsigned retries = 10000;
  38         /* read status bit - 0x8 offset */
  39         while (--retries && (in_be32(base_addr + 8) & (1 << 3)))
  40                 ;
  41
  42         /* Only attempt the iowrite if we didn't timeout */
  43         /* write to TX_FIFO - 0x4 offset */
  44         if (retries)
  45                 out_be32(base_addr + 4, c & 0xff);
  46 }
  47
  48 static void early_printk_write(struct console *unused,
  49                                         const char *s, unsigned n)
  50 {
  51         while (*s && n-- > 0) {
  52                 early_printk_putc(*s);
  53                 if (*s == '\n')
  54                         early_printk_putc('\r');
  55                 s++;
  56         }
  57 }
  58
  59 static struct console early_serial_console = {
  60         .name = "earlyser",
  61         .write = early_printk_write,
  62         .flags = CON_PRINTBUFFER,
  63         .index = -1,
  64 };
  65
  66 static struct console *early_console = &early_serial_console;
  67
  68 void early_printk(const char *fmt, ...)
  69 {
  70         char buf[512];
  71         int n;
  72         va_list ap;
  73
  74         if (early_console_initialized) {
  75                 va_start(ap, fmt);
  76                 n = vscnprintf(buf, 512, fmt, ap);
  77                 early_console->write(early_console, buf, n);
  78                 va_end(ap);
  79         }
  80 }
  81
  82 int __init setup_early_printk(char *opt)
  83 {
  84         if (early_console_initialized)
  85                 return 1;
  86
  87         base_addr = early_uartlite_console();
  88         if (base_addr) {
  89                 early_console_initialized = 1;
  90 #ifdef CONFIG_MMU
  91                 early_console_reg_tlb_alloc(base_addr);
  92 #endif
  93                 early_printk("early_printk_console is enabled at 0x%08x\n",
  94                                                         base_addr);
  95
  96                 /* register_console(early_console); */
  97
  98                 return 0;
  99         } else
 100                 return 1;
 101 }
 102
 103 void __init disable_early_printk(void)
 104 {
 105         if (!early_console_initialized || !early_console)
 106                 return;
 107         printk(KERN_WARNING "disabling early console\n");
 108         unregister_console(early_console);
 109         early_console_initialized = 0;
 110 }