1 /* 2 * Early serial console for 8250/16550 devices 3 * 4 * (c) Copyright 2004 Hewlett-Packard Development Company, L.P. 5 * Bjorn Helgaas <bjorn.helgaas@hp.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 * 11 * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King, 12 * and on early_printk.c by Andi Kleen. 13 * 14 * This is for use before the serial driver has initialized, in 15 * particular, before the UARTs have been discovered and named. 16 * Instead of specifying the console device as, e.g., "ttyS0", 17 * we locate the device directly by its MMIO or I/O port address. 18 * 19 * The user can specify the device directly, e.g., 20 * earlycon=uart8250,io,0x3f8,9600n8 21 * earlycon=uart8250,mmio,0xff5e0000,115200n8 22 * earlycon=uart8250,mmio32,0xff5e0000,115200n8 23 * or 24 * console=uart8250,io,0x3f8,9600n8 25 * console=uart8250,mmio,0xff5e0000,115200n8 26 * console=uart8250,mmio32,0xff5e0000,115200n8 27 */ 28 29 #include <linux/tty.h> 30 #include <linux/init.h> 31 #include <linux/console.h> 32 #include <linux/serial_core.h> 33 #include <linux/serial_reg.h> 34 #include <linux/serial.h> 35 #include <linux/serial_8250.h> 36 #include <asm/io.h> 37 #include <asm/serial.h> 38 #ifdef CONFIG_FIX_EARLYCON_MEM 39 #include <asm/pgtable.h> 40 #include <asm/fixmap.h> 41 #endif 42 43 struct early_serial8250_device { 44 struct uart_port port; 45 char options[16]; /* e.g., 115200n8 */ 46 unsigned int baud; 47 }; 48 49 static struct early_serial8250_device early_device; 50 51 unsigned int __weak __init serial8250_early_in(struct uart_port *port, int offset) 52 { 53 switch (port->iotype) { 54 case UPIO_MEM: 55 return readb(port->membase + offset); 56 case UPIO_MEM32: 57 return readl(port->membase + (offset << 2)); 58 case UPIO_PORT: 59 return inb(port->iobase + offset); 60 default: 61 return 0; 62 } 63 } 64 65 void __weak __init serial8250_early_out(struct uart_port *port, int offset, int value) 66 { 67 switch (port->iotype) { 68 case UPIO_MEM: 69 writeb(value, port->membase + offset); 70 break; 71 case UPIO_MEM32: 72 writel(value, port->membase + (offset << 2)); 73 break; 74 case UPIO_PORT: 75 outb(value, port->iobase + offset); 76 break; 77 } 78 } 79 80 #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) 81 82 static void __init wait_for_xmitr(struct uart_port *port) 83 { 84 unsigned int status; 85 86 for (;;) { 87 status = serial8250_early_in(port, UART_LSR); 88 if ((status & BOTH_EMPTY) == BOTH_EMPTY) 89 return; 90 cpu_relax(); 91 } 92 } 93 94 static void __init serial_putc(struct uart_port *port, int c) 95 { 96 wait_for_xmitr(port); 97 serial8250_early_out(port, UART_TX, c); 98 } 99 100 static void __init early_serial8250_write(struct console *console, 101 const char *s, unsigned int count) 102 { 103 struct uart_port *port = &early_device.port; 104 unsigned int ier; 105 106 /* Save the IER and disable interrupts */ 107 ier = serial8250_early_in(port, UART_IER); 108 serial8250_early_out(port, UART_IER, 0); 109 110 uart_console_write(port, s, count, serial_putc); 111 112 /* Wait for transmitter to become empty and restore the IER */ 113 wait_for_xmitr(port); 114 serial8250_early_out(port, UART_IER, ier); 115 } 116 117 static unsigned int __init probe_baud(struct uart_port *port) 118 { 119 unsigned char lcr, dll, dlm; 120 unsigned int quot; 121 122 lcr = serial8250_early_in(port, UART_LCR); 123 serial8250_early_out(port, UART_LCR, lcr | UART_LCR_DLAB); 124 dll = serial8250_early_in(port, UART_DLL); 125 dlm = serial8250_early_in(port, UART_DLM); 126 serial8250_early_out(port, UART_LCR, lcr); 127 128 quot = (dlm << 8) | dll; 129 return (port->uartclk / 16) / quot; 130 } 131 132 static void __init init_port(struct early_serial8250_device *device) 133 { 134 struct uart_port *port = &device->port; 135 unsigned int divisor; 136 unsigned char c; 137 138 serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */ 139 serial8250_early_out(port, UART_IER, 0); /* no interrupt */ 140 serial8250_early_out(port, UART_FCR, 0); /* no fifo */ 141 serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */ 142 143 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); 144 c = serial8250_early_in(port, UART_LCR); 145 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB); 146 serial8250_early_out(port, UART_DLL, divisor & 0xff); 147 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff); 148 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB); 149 } 150 151 static int __init parse_options(struct early_serial8250_device *device, 152 char *options) 153 { 154 struct uart_port *port = &device->port; 155 int mmio, mmio32, length; 156 157 if (!options) 158 return -ENODEV; 159 160 port->uartclk = BASE_BAUD * 16; 161 162 mmio = !strncmp(options, "mmio,", 5); 163 mmio32 = !strncmp(options, "mmio32,", 7); 164 if (mmio || mmio32) { 165 port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32); 166 port->mapbase = simple_strtoul(options + (mmio ? 5 : 7), 167 &options, 0); 168 if (mmio32) 169 port->regshift = 2; 170 #ifdef CONFIG_FIX_EARLYCON_MEM 171 set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, 172 port->mapbase & PAGE_MASK); 173 port->membase = 174 (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE); 175 port->membase += port->mapbase & ~PAGE_MASK; 176 #else 177 port->membase = ioremap_nocache(port->mapbase, 64); 178 if (!port->membase) { 179 printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n", 180 __func__, 181 (unsigned long long) port->mapbase); 182 return -ENOMEM; 183 } 184 #endif 185 } else if (!strncmp(options, "io,", 3)) { 186 port->iotype = UPIO_PORT; 187 port->iobase = simple_strtoul(options + 3, &options, 0); 188 mmio = 0; 189 } else 190 return -EINVAL; 191 192 options = strchr(options, ','); 193 if (options) { 194 options++; 195 device->baud = simple_strtoul(options, NULL, 0); 196 length = min(strcspn(options, " "), sizeof(device->options)); 197 strlcpy(device->options, options, length); 198 } else { 199 device->baud = probe_baud(port); 200 snprintf(device->options, sizeof(device->options), "%u", 201 device->baud); 202 } 203 204 if (mmio || mmio32) 205 printk(KERN_INFO 206 "Early serial console at MMIO%s 0x%llx (options '%s')\n", 207 mmio32 ? "32" : "", 208 (unsigned long long)port->mapbase, 209 device->options); 210 else 211 printk(KERN_INFO 212 "Early serial console at I/O port 0x%lx (options '%s')\n", 213 port->iobase, 214 device->options); 215 216 return 0; 217 } 218 219 static struct console early_serial8250_console __initdata = { 220 .name = "uart", 221 .write = early_serial8250_write, 222 .flags = CON_PRINTBUFFER | CON_BOOT, 223 .index = -1, 224 }; 225 226 static int __init early_serial8250_setup(char *options) 227 { 228 struct early_serial8250_device *device = &early_device; 229 int err; 230 231 if (device->port.membase || device->port.iobase) 232 return 0; 233 234 err = parse_options(device, options); 235 if (err < 0) 236 return err; 237 238 init_port(device); 239 return 0; 240 } 241 242 int __init setup_early_serial8250_console(char *cmdline) 243 { 244 char *options; 245 int err; 246 247 options = strstr(cmdline, "uart8250,"); 248 if (!options) { 249 options = strstr(cmdline, "uart,"); 250 if (!options) 251 return 0; 252 } 253 254 options = strchr(cmdline, ',') + 1; 255 err = early_serial8250_setup(options); 256 if (err < 0) 257 return err; 258 259 register_console(&early_serial8250_console); 260 261 return 0; 262 } 263 264 int serial8250_find_port_for_earlycon(void) 265 { 266 struct early_serial8250_device *device = &early_device; 267 struct uart_port *port = &device->port; 268 int line; 269 int ret; 270 271 if (!device->port.membase && !device->port.iobase) 272 return -ENODEV; 273 274 line = serial8250_find_port(port); 275 if (line < 0) 276 return -ENODEV; 277 278 ret = update_console_cmdline("uart", 8250, 279 "ttyS", line, device->options); 280 if (ret < 0) 281 ret = update_console_cmdline("uart", 0, 282 "ttyS", line, device->options); 283 284 return ret; 285 } 286 287 early_param("earlycon", setup_early_serial8250_console); 288