/*
* 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_nocache(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);
