arch/nios2/kernel/early_printk.c

   1 /*
   2  * Early printk for Nios2.
   3  *
   4  * Copyright (C) 2015, Altera Corporation
   5  * Copyright (C) 2010, Tobias Klauser <tklauser@distanz.ch>
   6  * Copyright (C) 2009, Wind River Systems Inc
   7  *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License. See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  */
  13
  14 #include <linux/console.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/io.h>
  18
  19 #include <asm/prom.h>
  20
  21 static unsigned long base_addr;
  22
  23 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE)
  24
  25 #define ALTERA_JTAGUART_DATA_REG                0
  26 #define ALTERA_JTAGUART_CONTROL_REG             4
  27 #define ALTERA_JTAGUART_CONTROL_WSPACE_MSK      0xFFFF0000
  28 #define ALTERA_JTAGUART_CONTROL_AC_MSK          0x00000400
  29
  30 #define JUART_GET_CR() \
  31         __builtin_ldwio((void *)(base_addr + ALTERA_JTAGUART_CONTROL_REG))
  32 #define JUART_SET_CR(v) \
  33         __builtin_stwio((void *)(base_addr + ALTERA_JTAGUART_CONTROL_REG), v)
  34 #define JUART_SET_TX(v) \
  35         __builtin_stwio((void *)(base_addr + ALTERA_JTAGUART_DATA_REG), v)
  36
  37 static void early_console_write(struct console *con, const char *s, unsigned n)
  38 {
  39         unsigned long status;
  40
  41         while (n-- && *s) {
  42                 while (((status = JUART_GET_CR())
  43                                 & ALTERA_JTAGUART_CONTROL_WSPACE_MSK) == 0) {
  44 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
  45                         if ((status & ALTERA_JTAGUART_CONTROL_AC_MSK) == 0)
  46                                 return; /* no connection activity */
  47 #endif
  48                 }
  49                 JUART_SET_TX(*s);
  50                 s++;
  51         }
  52 }
  53
  54 #elif defined(CONFIG_SERIAL_ALTERA_UART_CONSOLE)
  55
  56 #define ALTERA_UART_TXDATA_REG          4
  57 #define ALTERA_UART_STATUS_REG          8
  58 #define ALTERA_UART_STATUS_TRDY         0x0040
  59
  60 #define UART_GET_SR() \
  61         __builtin_ldwio((void *)(base_addr + ALTERA_UART_STATUS_REG))
  62 #define UART_SET_TX(v) \
  63         __builtin_stwio((void *)(base_addr + ALTERA_UART_TXDATA_REG), v)
  64
  65 static void early_console_putc(char c)
  66 {
  67         while (!(UART_GET_SR() & ALTERA_UART_STATUS_TRDY))
  68                 ;
  69
  70         UART_SET_TX(c);
  71 }
  72
  73 static void early_console_write(struct console *con, const char *s, unsigned n)
  74 {
  75         while (n-- && *s) {
  76                 early_console_putc(*s);
  77                 if (*s == '\n')
  78                         early_console_putc('\r');
  79                 s++;
  80         }
  81 }
  82
  83 #else
  84 # error Neither SERIAL_ALTERA_JTAGUART_CONSOLE nor SERIAL_ALTERA_UART_CONSOLE \
  85 selected
  86 #endif
  87
  88 static struct console early_console_prom = {
  89         .name   = "early",
  90         .write  = early_console_write,
  91         .flags  = CON_PRINTBUFFER | CON_BOOT,
  92         .index  = -1
  93 };
  94
  95 void __init setup_early_printk(void)
  96 {
  97 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE) ||   \
  98         defined(CONFIG_SERIAL_ALTERA_UART_CONSOLE)
  99         base_addr = of_early_console();
 100 #else
 101         base_addr = 0;
 102 #endif
 103
 104         if (!base_addr)
 105                 return;
 106
 107 #if defined(CONFIG_SERIAL_ALTERA_JTAGUART_CONSOLE_BYPASS)
 108         /* Clear activity bit so BYPASS doesn't stall if we've used JTAG for
 109          * downloading the kernel. This might cause early data to be lost even
 110          * if the JTAG terminal is running.
 111          */
 112         JUART_SET_CR(JUART_GET_CR() | ALTERA_JTAGUART_CONTROL_AC_MSK);
 113 #endif
 114
 115         early_console = &early_console_prom;
 116         register_console(early_console);
 117         pr_info("early_console initialized at 0x%08lx\n", base_addr);
 118 }