/* * Early serial console for 8250/16550 devices * * (c) Copyright 2004 Hewlett-Packard Development Company, L.P. * Bjorn Helgaas <bjorn.helgaas@hp.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King, * and on early_printk.c by Andi Kleen. * * This is for use before the serial driver has initialized, in * particular, before the UARTs have been discovered and named. * Instead of specifying the console device as, e.g., "ttyS0", * we locate the device directly by its MMIO or I/O port address. * * The user can specify the device directly, e.g., * earlycon=uart8250,io,0x3f8,9600n8 * earlycon=uart8250,mmio,0xff5e0000,115200n8 * or * console=uart8250,io,0x3f8,9600n8 * console=uart8250,mmio,0xff5e0000,115200n8 */ #include <linux/tty.h> #include <linux/init.h> #include <linux/console.h> #include <linux/serial_core.h> #include <linux/serial_reg.h> #include <linux/serial.h> #include <linux/serial_8250.h> #include <asm/io.h> #include <asm/serial.h> #ifdef CONFIG_FIX_EARLYCON_MEM #include <asm/pgtable.h> #include <asm/fixmap.h> #endif struct early_serial8250_device { struct uart_port port; char options[16]; /* e.g., 115200n8 */ unsigned int baud; }; static struct early_serial8250_device early_device; static unsigned int __init serial_in(struct uart_port *port, int offset) { if (port->iotype == UPIO_MEM) return readb(port->membase + offset); else return inb(port->iobase + offset); } static void __init serial_out(struct uart_port *port, int offset, int value) { if (port->iotype == UPIO_MEM) writeb(value, port->membase + offset); else outb(value, port->iobase + offset); } #define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) static void __init wait_for_xmitr(struct uart_port *port) { unsigned int status; for (;;) { status = serial_in(port, UART_LSR); if ((status & BOTH_EMPTY) == BOTH_EMPTY) return; cpu_relax(); } } static void __init serial_putc(struct uart_port *port, int c) { wait_for_xmitr(port); serial_out(port, UART_TX, c); } static void __init early_serial8250_write(struct console *console, const char *s, unsigned int count) { struct uart_port *port = &early_device.port; unsigned int ier; /* Save the IER and disable interrupts */ ier = serial_in(port, UART_IER); serial_out(port, UART_IER, 0); uart_console_write(port, s, count, serial_putc); /* Wait for transmitter to become empty and restore the IER */ wait_for_xmitr(port); serial_out(port, UART_IER, ier); } static unsigned int __init probe_baud(struct uart_port *port) { unsigned char lcr, dll, dlm; unsigned int quot; lcr = serial_in(port, UART_LCR); serial_out(port, UART_LCR, lcr | UART_LCR_DLAB); dll = serial_in(port, UART_DLL); dlm = serial_in(port, UART_DLM); serial_out(port, UART_LCR, lcr); quot = (dlm << 8) | dll; return (port->uartclk / 16) / quot; } static void __init init_port(struct early_serial8250_device *device) { struct uart_port *port = &device->port; unsigned int divisor; unsigned char c; serial_out(port, UART_LCR, 0x3); /* 8n1 */ serial_out(port, UART_IER, 0); /* no interrupt */ serial_out(port, UART_FCR, 0); /* no fifo */ serial_out(port, UART_MCR, 0x3); /* DTR + RTS */ divisor = port->uartclk / (16 * device->baud); c = serial_in(port, UART_LCR); serial_out(port, UART_LCR, c | UART_LCR_DLAB); serial_out(port, UART_DLL, divisor & 0xff); serial_out(port, UART_DLM, (divisor >> 8) & 0xff); serial_out(port, UART_LCR, c & ~UART_LCR_DLAB); } static int __init parse_options(struct early_serial8250_device *device, char *options) { struct uart_port *port = &device->port; int mmio, length; if (!options) return -ENODEV; port->uartclk = BASE_BAUD * 16; if (!strncmp(options, "mmio,", 5)) { port->iotype = UPIO_MEM; port->mapbase = simple_strtoul(options + 5, &options, 0); #ifdef CONFIG_FIX_EARLYCON_MEM set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, port->mapbase & PAGE_MASK); port->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE); port->membase += port->mapbase & ~PAGE_MASK; #else port->membase = ioremap(port->mapbase, 64); if (!port->membase) { printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n", __FUNCTION__, (unsigned long long)port->mapbase); return -ENOMEM; } #endif mmio = 1; } else if (!strncmp(options, "io,", 3)) { port->iotype = UPIO_PORT; port->iobase = simple_strtoul(options + 3, &options, 0); mmio = 0; } else return -EINVAL; options = strchr(options, ','); if (options) { options++; device->baud = simple_strtoul(options, NULL, 0); length = min(strcspn(options, " "), sizeof(device->options)); strncpy(device->options, options, length); } else { device->baud = probe_baud(port); snprintf(device->options, sizeof(device->options), "%u", device->baud); } printk(KERN_INFO "Early serial console at %s 0x%llx (options '%s')\n", mmio ? "MMIO" : "I/O port", mmio ? (unsigned long long) port->mapbase : (unsigned long long) port->iobase, device->options); return 0; } static struct console early_serial8250_console __initdata = { .name = "uart", .write = early_serial8250_write, .flags = CON_PRINTBUFFER | CON_BOOT, .index = -1, }; static int __init early_serial8250_setup(char *options) { struct early_serial8250_device *device = &early_device; int err; if (device->port.membase || device->port.iobase) return 0; err = parse_options(device, options); if (err < 0) return err; init_port(device); return 0; } int __init setup_early_serial8250_console(char *cmdline) { char *options; int err; options = strstr(cmdline, "uart8250,"); if (!options) { options = strstr(cmdline, "uart,"); if (!options) return 0; } options = strchr(cmdline, ',') + 1; err = early_serial8250_setup(options); if (err < 0) return err; register_console(&early_serial8250_console); return 0; } int serial8250_find_port_for_earlycon(void) { struct early_serial8250_device *device = &early_device; struct uart_port *port = &device->port; int line; int ret; if (!device->port.membase && !device->port.iobase) return -ENODEV; line = serial8250_find_port(port); if (line < 0) return -ENODEV; ret = update_console_cmdline("uart", 8250, "ttyS", line, device->options); if (ret < 0) ret = update_console_cmdline("uart", 0, "ttyS", line, device->options); return ret; } early_param("earlycon", setup_early_serial8250_console);