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, " ") + 1, 197 (size_t)(sizeof(device->options))); 198 strlcpy(device->options, options, length); 199 } else { 200 device->baud = probe_baud(port); 201 snprintf(device->options, sizeof(device->options), "%u", 202 device->baud); 203 } 204 205 if (mmio || mmio32) 206 printk(KERN_INFO 207 "Early serial console at MMIO%s 0x%llx (options '%s')\n", 208 mmio32 ? "32" : "", 209 (unsigned long long)port->mapbase, 210 device->options); 211 else 212 printk(KERN_INFO 213 "Early serial console at I/O port 0x%lx (options '%s')\n", 214 port->iobase, 215 device->options); 216 217 return 0; 218 } 219 220 static struct console early_serial8250_console __initdata = { 221 .name = "uart", 222 .write = early_serial8250_write, 223 .flags = CON_PRINTBUFFER | CON_BOOT, 224 .index = -1, 225 }; 226 227 static int __init early_serial8250_setup(char *options) 228 { 229 struct early_serial8250_device *device = &early_device; 230 int err; 231 232 if (device->port.membase || device->port.iobase) 233 return 0; 234 235 err = parse_options(device, options); 236 if (err < 0) 237 return err; 238 239 init_port(device); 240 return 0; 241 } 242 243 int __init setup_early_serial8250_console(char *cmdline) 244 { 245 char *options; 246 int err; 247 248 options = strstr(cmdline, "uart8250,"); 249 if (!options) { 250 options = strstr(cmdline, "uart,"); 251 if (!options) 252 return 0; 253 } 254 255 options = strchr(cmdline, ',') + 1; 256 err = early_serial8250_setup(options); 257 if (err < 0) 258 return err; 259 260 register_console(&early_serial8250_console); 261 262 return 0; 263 } 264 265 int serial8250_find_port_for_earlycon(void) 266 { 267 struct early_serial8250_device *device = &early_device; 268 struct uart_port *port = &device->port; 269 int line; 270 int ret; 271 272 if (!device->port.membase && !device->port.iobase) 273 return -ENODEV; 274 275 line = serial8250_find_port(port); 276 if (line < 0) 277 return -ENODEV; 278 279 ret = update_console_cmdline("uart", 8250, 280 "ttyS", line, device->options); 281 if (ret < 0) 282 ret = update_console_cmdline("uart", 0, 283 "ttyS", line, device->options); 284 285 return ret; 286 } 287 288 early_param("earlycon", setup_early_serial8250_console); 289