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 base_addr;
  25
  26 #ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
  27 static void early_printk_uartlite_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 = 1000000;
  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_uartlite_write(struct console *unused,
  49                                         const char *s, unsigned n)
  50 {
  51         while (*s && n-- > 0) {
  52                 if (*s == '\n')
  53                         early_printk_uartlite_putc('\r');
  54                 early_printk_uartlite_putc(*s);
  55                 s++;
  56         }
  57 }
  58
  59 static struct console early_serial_uartlite_console = {
  60         .name = "earlyser",
  61         .write = early_printk_uartlite_write,
  62         .flags = CON_PRINTBUFFER | CON_BOOT,
  63         .index = -1,
  64 };
  65 #endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
  66
  67 #ifdef CONFIG_SERIAL_8250_CONSOLE
  68 static void early_printk_uart16550_putc(char c)
  69 {
  70         /*
  71          * Limit how many times we'll spin waiting for TX FIFO status.
  72          * This will prevent lockups if the base address is incorrectly
  73          * set, or any other issue on the UARTLITE.
  74          * This limit is pretty arbitrary, unless we are at about 10 baud
  75          * we'll never timeout on a working UART.
  76          */
  77
  78         #define UART_LSR_TEMT   0x40 /* Transmitter empty */
  79         #define UART_LSR_THRE   0x20 /* Transmit-hold-register empty */
  80         #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
  81
  82         unsigned retries = 10000;
  83
  84         while (--retries &&
  85                 !((in_be32(base_addr + 0x14) & BOTH_EMPTY) == BOTH_EMPTY))
  86                 ;
  87
  88         if (retries)
  89                 out_be32(base_addr, c & 0xff);
  90 }
  91
  92 static void early_printk_uart16550_write(struct console *unused,
  93                                         const char *s, unsigned n)
  94 {
  95         while (*s && n-- > 0) {
  96                 if (*s == '\n')
  97                         early_printk_uart16550_putc('\r');
  98                 early_printk_uart16550_putc(*s);
  99                 s++;
 100         }
 101 }
 102
 103 static struct console early_serial_uart16550_console = {
 104         .name = "earlyser",
 105         .write = early_printk_uart16550_write,
 106         .flags = CON_PRINTBUFFER | CON_BOOT,
 107         .index = -1,
 108 };
 109 #endif /* CONFIG_SERIAL_8250_CONSOLE */
 110
 111 int __init setup_early_printk(char *opt)
 112 {
 113         int version = 0;
 114
 115         if (early_console)
 116                 return 1;
 117
 118         base_addr = of_early_console(&version);
 119         if (base_addr) {
 120 #ifdef CONFIG_MMU
 121                 early_console_reg_tlb_alloc(base_addr);
 122 #endif
 123                 switch (version) {
 124 #ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
 125                 case UARTLITE:
 126                         pr_info("Early console on uartlite at 0x%08x\n",
 127                                                                 base_addr);
 128                         early_console = &early_serial_uartlite_console;
 129                         break;
 130 #endif
 131 #ifdef CONFIG_SERIAL_8250_CONSOLE
 132                 case UART16550:
 133                         pr_info("Early console on uart16650 at 0x%08x\n",
 134                                                                 base_addr);
 135                         early_console = &early_serial_uart16550_console;
 136                         break;
 137 #endif
 138                 default:
 139                         pr_info("Unsupported early console %d\n",
 140                                                                 version);
 141                         return 1;
 142                 }
 143
 144                 register_console(early_console);
 145                 return 0;
 146         }
 147         return 1;
 148 }
 149
 150 /* Remap early console to virtual address and do not allocate one TLB
 151  * only for early console because of performance degression */
 152 void __init remap_early_printk(void)
 153 {
 154         if (!early_console)
 155                 return;
 156         pr_info("early_printk_console remapping from 0x%x to ", base_addr);
 157         base_addr = (u32) ioremap(base_addr, PAGE_SIZE);
 158         pr_cont("0x%x\n", base_addr);
 159
 160 #ifdef CONFIG_MMU
 161         /*
 162          * Early console is on the top of skipped TLB entries
 163          * decrease tlb_skip size ensure that hardcoded TLB entry will be
 164          * used by generic algorithm
 165          * FIXME check if early console mapping is on the top by rereading
 166          * TLB entry and compare baseaddr
 167          *  mts  rtlbx, (tlb_skip - 1)
 168          *  nop
 169          *  mfs  rX, rtlblo
 170          *  nop
 171          *  cmp rX, orig_base_addr
 172          */
 173         tlb_skip -= 1;
 174 #endif
 175 }
 176
 177 void __init disable_early_printk(void)
 178 {
 179         if (!early_console)
 180                 return;
 181         pr_warn("disabling early console\n");
 182         unregister_console(early_console);
 183         early_console = NULL;
 184 }