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Linux/arch/microblaze/kernel/early_printk.c

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  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 }
185 

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