diff options
Diffstat (limited to 'drivers/serial/8250_early.c')
| -rw-r--r-- | drivers/serial/8250_early.c | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/drivers/serial/8250_early.c b/drivers/serial/8250_early.c new file mode 100644 index 000000000000..b7a5dd710228 --- /dev/null +++ b/drivers/serial/8250_early.c @@ -0,0 +1,255 @@ +/* + * 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., + * console=uart,io,0x3f8,9600n8 + * console=uart,mmio,0xff5e0000,115200n8 + * or platform code can call early_uart_console_init() to set + * the early UART device. + * + * After the normal serial driver starts, we try to locate the + * matching ttyS device and start a console there. + */ + +#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 <asm/io.h> +#include <asm/serial.h> + +struct early_uart_device { + struct uart_port port; + char options[16]; /* e.g., 115200n8 */ + unsigned int baud; +}; + +static struct early_uart_device early_device __initdata; +static int early_uart_registered __initdata; + +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 putc(struct uart_port *port, unsigned char c) +{ + wait_for_xmitr(port); + serial_out(port, UART_TX, c); +} + +static void __init early_uart_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); + + while (*s && count-- > 0) { + putc(port, *s); + if (*s == '\n') + putc(port, '\r'); + s++; + } + + /* 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_uart_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_uart_device *device, char *options) +{ + struct uart_port *port = &device->port; + int mapsize = 64; + 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); + port->membase = ioremap(port->mapbase, mapsize); + if (!port->membase) { + printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n", + __FUNCTION__, port->mapbase); + return -ENOMEM; + } + 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; + + if ((options = strchr(options, ','))) { + options++; + device->baud = simple_strtoul(options, 0, 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%lx (options '%s')\n", + mmio ? "MMIO" : "I/O port", + mmio ? port->mapbase : (unsigned long) port->iobase, + device->options); + return 0; +} + +static int __init early_uart_setup(struct console *console, char *options) +{ + struct early_uart_device *device = &early_device; + int err; + + if (device->port.membase || device->port.iobase) + return 0; + + if ((err = parse_options(device, options)) < 0) + return err; + + init_port(device); + return 0; +} + +static struct console early_uart_console __initdata = { + .name = "uart", + .write = early_uart_write, + .setup = early_uart_setup, + .flags = CON_PRINTBUFFER, + .index = -1, +}; + +static int __init early_uart_console_init(void) +{ + if (!early_uart_registered) { + register_console(&early_uart_console); + early_uart_registered = 1; + } + return 0; +} +console_initcall(early_uart_console_init); + +int __init early_serial_console_init(char *cmdline) +{ + char *options; + int err; + + options = strstr(cmdline, "console=uart,"); + if (!options) + return -ENODEV; + + options = strchr(cmdline, ',') + 1; + if ((err = early_uart_setup(NULL, options)) < 0) + return err; + return early_uart_console_init(); +} + +static int __init early_uart_console_switch(void) +{ + struct early_uart_device *device = &early_device; + struct uart_port *port = &device->port; + int mmio, line; + + if (!(early_uart_console.flags & CON_ENABLED)) + return 0; + + /* Try to start the normal driver on a matching line. */ + mmio = (port->iotype == UPIO_MEM); + line = serial8250_start_console(port, device->options); + if (line < 0) + printk("No ttyS device at %s 0x%lx for console\n", + mmio ? "MMIO" : "I/O port", + mmio ? port->mapbase : + (unsigned long) port->iobase); + + unregister_console(&early_uart_console); + if (mmio) + iounmap(port->membase); + + return 0; +} +late_initcall(early_uart_console_switch); |