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 #ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
  28 static void early_printk_uartlite_putc(char c)
  29 {
  30         /*
  31          * Limit how many times we'll spin waiting for TX FIFO status.
  32          * This will prevent lockups if the base address is incorrectly
  33          * set, or any other issue on the UARTLITE.
  34          * This limit is pretty arbitrary, unless we are at about 10 baud
  35          * we'll never timeout on a working UART.
  36          */
  37
  38         unsigned retries = 10000;
  39         /* read status bit - 0x8 offset */
  40         while (--retries && (in_be32(base_addr + 8) & (1 << 3)))
  41                 ;
  42
  43         /* Only attempt the iowrite if we didn't timeout */
  44         /* write to TX_FIFO - 0x4 offset */
  45         if (retries)
  46                 out_be32(base_addr + 4, c & 0xff);
  47 }
  48
  49 static void early_printk_uartlite_write(struct console *unused,
  50                                         const char *s, unsigned n)
  51 {
  52         while (*s && n-- > 0) {
  53                 early_printk_uartlite_putc(*s);
  54                 if (*s == '\n')
  55                         early_printk_uartlite_putc('\r');
  56                 s++;
  57         }
  58 }
  59
  60 static struct console early_serial_uartlite_console = {
  61         .name = "earlyser",
  62         .write = early_printk_uartlite_write,
  63         .flags = CON_PRINTBUFFER,
  64         .index = -1,
  65 };
  66 #endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
  67
  68 #ifdef CONFIG_SERIAL_8250_CONSOLE
  69 static void early_printk_uart16550_putc(char c)
  70 {
  71         /*
  72          * Limit how many times we'll spin waiting for TX FIFO status.
  73          * This will prevent lockups if the base address is incorrectly
  74          * set, or any other issue on the UARTLITE.
  75          * This limit is pretty arbitrary, unless we are at about 10 baud
  76          * we'll never timeout on a working UART.
  77          */
  78
  79         #define UART_LSR_TEMT   0x40 /* Transmitter empty */
  80         #define UART_LSR_THRE   0x20 /* Transmit-hold-register empty */
  81         #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  82
  83         unsigned retries = 10000;
  84
  85         while (--retries &&
  86                 !((in_be32(base_addr + 0x14) & BOTH_EMPTY) == BOTH_EMPTY))
  87                 ;
  88
  89         if (retries)
  90                 out_be32(base_addr, c & 0xff);
  91 }
  92
  93 static void early_printk_uart16550_write(struct console *unused,
  94                                         const char *s, unsigned n)
  95 {
  96         while (*s && n-- > 0) {
  97                 early_printk_uart16550_putc(*s);
  98                 if (*s == '\n')
  99                         early_printk_uart16550_putc('\r');
 100                 s++;
 101         }
 102 }
 103
 104 static struct console early_serial_uart16550_console = {
 105         .name = "earlyser",
 106         .write = early_printk_uart16550_write,
 107         .flags = CON_PRINTBUFFER,
 108         .index = -1,
 109 };
 110 #endif /* CONFIG_SERIAL_8250_CONSOLE */
 111
 112 static struct console *early_console;
 113
 114 void early_printk(const char *fmt, ...)
 115 {
 116         char buf[512];
 117         int n;
 118         va_list ap;
 119
 120         if (early_console_initialized) {
 121                 va_start(ap, fmt);
 122                 n = vscnprintf(buf, 512, fmt, ap);
 123                 early_console->write(early_console, buf, n);
 124                 va_end(ap);
 125         }
 126 }
 127
 128 int __init setup_early_printk(char *opt)
 129 {
 130         if (early_console_initialized)
 131                 return 1;
 132
 133 #ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
 134         base_addr = early_uartlite_console();
 135         if (base_addr) {
 136                 early_console_initialized = 1;
 137 #ifdef CONFIG_MMU
 138                 early_console_reg_tlb_alloc(base_addr);
 139 #endif
 140                 early_console = &early_serial_uartlite_console;
 141                 early_printk("early_printk_console is enabled at 0x%08x\n",
 142                                                         base_addr);
 143
 144                 /* register_console(early_console); */
 145
 146                 return 0;
 147         }
 148 #endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
 149
 150 #ifdef CONFIG_SERIAL_8250_CONSOLE
 151         base_addr = early_uart16550_console();
 152         base_addr &= ~3; /* clear register offset */
 153         if (base_addr) {
 154                 early_console_initialized = 1;
 155 #ifdef CONFIG_MMU
 156                 early_console_reg_tlb_alloc(base_addr);
 157 #endif
 158                 early_console = &early_serial_uart16550_console;
 159
 160                 early_printk("early_printk_console is enabled at 0x%08x\n",
 161                                                         base_addr);
 162
 163                 /* register_console(early_console); */
 164
 165                 return 0;
 166         }
 167 #endif /* CONFIG_SERIAL_8250_CONSOLE */
 168
 169         return 1;
 170 }
 171
 172 void __init disable_early_printk(void)
 173 {
 174         if (!early_console_initialized || !early_console)
 175                 return;
 176         printk(KERN_WARNING "disabling early console\n");
 177         unregister_console(early_console);
 178         early_console_initialized = 0;
 179 }