| /* |
| * 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", |
| __func__, |
| (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); |