diff options
Diffstat (limited to 'drivers/tty/serial/8250/8250_early.c')
| -rw-r--r-- | drivers/tty/serial/8250/8250_early.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c new file mode 100644 index 00000000000..4858b8a99d3 --- /dev/null +++ b/drivers/tty/serial/8250/8250_early.c @@ -0,0 +1,193 @@ +/* + * 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 + * earlycon=uart8250,mmio32,0xff5e0000,115200n8 + * or + * console=uart8250,io,0x3f8,9600n8 + * console=uart8250,mmio,0xff5e0000,115200n8 + * console=uart8250,mmio32,0xff5e0000,115200n8 + */ + +#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> + +static struct earlycon_device *early_device; + +unsigned int __weak __init serial8250_early_in(struct uart_port *port, int offset) +{ + switch (port->iotype) { + case UPIO_MEM: + return readb(port->membase + offset); + case UPIO_MEM32: + return readl(port->membase + (offset << 2)); + case UPIO_PORT: + return inb(port->iobase + offset); + default: + return 0; + } +} + +void __weak __init serial8250_early_out(struct uart_port *port, int offset, int value) +{ + switch (port->iotype) { + case UPIO_MEM: + writeb(value, port->membase + offset); + break; + case UPIO_MEM32: + writel(value, port->membase + (offset << 2)); + break; + case UPIO_PORT: + outb(value, port->iobase + offset); + break; + } +} + +#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE) + +static void __init wait_for_xmitr(struct uart_port *port) +{ + unsigned int status; + + for (;;) { + status = serial8250_early_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); + serial8250_early_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 = serial8250_early_in(port, UART_IER); + serial8250_early_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); + serial8250_early_out(port, UART_IER, ier); +} + +static unsigned int __init probe_baud(struct uart_port *port) +{ + unsigned char lcr, dll, dlm; + unsigned int quot; + + lcr = serial8250_early_in(port, UART_LCR); + serial8250_early_out(port, UART_LCR, lcr | UART_LCR_DLAB); + dll = serial8250_early_in(port, UART_DLL); + dlm = serial8250_early_in(port, UART_DLM); + serial8250_early_out(port, UART_LCR, lcr); + + quot = (dlm << 8) | dll; + return (port->uartclk / 16) / quot; +} + +static void __init init_port(struct earlycon_device *device) +{ + struct uart_port *port = &device->port; + unsigned int divisor; + unsigned char c; + + serial8250_early_out(port, UART_LCR, 0x3); /* 8n1 */ + serial8250_early_out(port, UART_IER, 0); /* no interrupt */ + serial8250_early_out(port, UART_FCR, 0); /* no fifo */ + serial8250_early_out(port, UART_MCR, 0x3); /* DTR + RTS */ + + divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud); + c = serial8250_early_in(port, UART_LCR); + serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB); + serial8250_early_out(port, UART_DLL, divisor & 0xff); + serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff); + serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB); +} + +static int __init early_serial8250_setup(struct earlycon_device *device, + const char *options) +{ + if (!(device->port.membase || device->port.iobase)) + return 0; + + if (!device->baud) { + device->baud = probe_baud(&device->port); + snprintf(device->options, sizeof(device->options), "%u", + device->baud); + } + + init_port(device); + + early_device = device; + device->con->write = early_serial8250_write; + return 0; +} +EARLYCON_DECLARE(uart8250, early_serial8250_setup); +EARLYCON_DECLARE(uart, early_serial8250_setup); + +int __init setup_early_serial8250_console(char *cmdline) +{ + char match[] = "uart8250"; + + if (cmdline && cmdline[4] == ',') + match[4] = '\0'; + + return setup_earlycon(cmdline, match, early_serial8250_setup); +} + +int serial8250_find_port_for_earlycon(void) +{ + struct earlycon_device *device = early_device; + struct uart_port *port = device ? &device->port : NULL; + int line; + int ret; + + if (!port || (!port->membase && !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; +} |