arch/blackfin/kernel/shadow_console.c

   1 /*
   2  * manage a small early shadow of the log buffer which we can pass between the
   3  * bootloader so early crash messages are communicated properly and easily
   4  *
   5  * Copyright 2009 Analog Devices Inc.
   6  *
   7  * Licensed under the GPL-2 or later.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/init.h>
  12 #include <linux/console.h>
  13 #include <linux/string.h>
  14 #include <asm/blackfin.h>
  15 #include <asm/irq_handler.h>
  16 #include <asm/early_printk.h>
  17
  18 #define SHADOW_CONSOLE_START            (0x500)
  19 #define SHADOW_CONSOLE_END              (0x1000)
  20 #define SHADOW_CONSOLE_MAGIC_LOC        (0x4F0)
  21 #define SHADOW_CONSOLE_MAGIC            (0xDEADBEEF)
  22
  23 static __initdata char *shadow_console_buffer = (char *)SHADOW_CONSOLE_START;
  24
  25 __init void early_shadow_write(struct console *con, const char *s,
  26                                 unsigned int n)
  27 {
  28         unsigned int i;
  29         /*
  30          * save 2 bytes for the double null at the end
  31          * once we fail on a long line, make sure we don't write a short line afterwards
  32          */
  33         if ((shadow_console_buffer + n) <= (char *)(SHADOW_CONSOLE_END - 2)) {
  34                 /* can't use memcpy - it may not be relocated yet */
  35                 for (i = 0; i <= n; i++)
  36                         shadow_console_buffer[i] = s[i];
  37                 shadow_console_buffer += n;
  38                 shadow_console_buffer[0] = 0;
  39                 shadow_console_buffer[1] = 0;
  40         } else
  41                 shadow_console_buffer = (char *)SHADOW_CONSOLE_END;
  42 }
  43
  44 static __initdata struct console early_shadow_console = {
  45         .name = "early_shadow",
  46         .write = early_shadow_write,
  47         .flags = CON_BOOT | CON_PRINTBUFFER,
  48         .index = -1,
  49         .device = 0,
  50 };
  51
  52 __init int shadow_console_enabled(void)
  53 {
  54         return early_shadow_console.flags & CON_ENABLED;
  55 }
  56
  57 __init void mark_shadow_error(void)
  58 {
  59         int *loc = (int *)SHADOW_CONSOLE_MAGIC_LOC;
  60         loc[0] = SHADOW_CONSOLE_MAGIC;
  61         loc[1] = SHADOW_CONSOLE_START;
  62 }
  63
  64 __init void enable_shadow_console(void)
  65 {
  66         if (!shadow_console_enabled()) {
  67                 register_console(&early_shadow_console);
  68                 /* for now, assume things are going to fail */
  69                 mark_shadow_error();
  70         }
  71 }
  72
  73 static __init int disable_shadow_console(void)
  74 {
  75         /*
  76          * by the time pure_initcall runs, the standard console is enabled,
  77          * and the early_console is off, so unset the magic numbers
  78          * unregistering the console is taken care of in common code (See
  79          * ./kernel/printk:disable_boot_consoles() )
  80          */
  81         int *loc = (int *)SHADOW_CONSOLE_MAGIC_LOC;
  82
  83         loc[0] = 0;
  84
  85         return 0;
  86 }
  87 pure_initcall(disable_shadow_console);
  88
  89 /*
  90  * since we can't use printk, dump numbers (as hex), n = # bits
  91  */
  92 __init void early_shadow_reg(unsigned long reg, unsigned int n)
  93 {
  94         /*
  95          * can't use any "normal" kernel features, since thay
  96          * may not be relocated to their execute address yet
  97          */
  98         int i;
  99         char ascii[11] = " 0x";
 100
 101         n = n / 4;
 102         reg = reg << ((8 - n) * 4);
 103         n += 3;
 104
 105         for (i = 3; i <= n ; i++) {
 106                 ascii[i] = hex_asc_lo(reg >> 28);
 107                 reg <<= 4;
 108         }
 109         early_shadow_write(NULL, ascii, n);
 110
 111 }